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(5 MAR 2018)

We undertook a comprehensive project over the last 8 weeks to perform an unbiased, independent, full product and performance review, of the 3 major players in the Fat Bike suspension fork market.

In order to perform a fair and unbiased review, several BASELINES needed to be established, to make the test fair for all competitors. provided all necessary gear and suspension forks to independent riders and asked them to do all their independent testing offsite, while recording their results.  If the product testers ran into component issues, found operating condition limitations, or product failures, the data was sent back to to review and attempt to replicate these conditions using our own equipment.  In every instance, we were able to duplicate and validate their findings on at least 2 or 3 bikes, so the results are vetted through multiple sources confirming the statistical and performance review data was accurate. will publish the Lead Independent Tester's full review unaltered and in it's entirety. 

Before and after the actual review article, will introduce the background information and performance baselines for the test.  We will only include supplementary comments, charts, pictures, and provide product and performance clarifications (like direct communications with the manufacturers or factories during testing), to help tell the story of this product review, and answer questions the Independent Testers ran into during the testing process.

The decision, of which suspension fork won the shootout review, is completely the decision of the lead independent tester.

We completely support their independent decision and will publish their complete report for the sake of transparency. is the only retailer in CANADA that sells *all three models* of the suspension forks in this test.  We thought we owed it to our customers to perform this review, so they had the best buying options possible. shares information, and our goal is three-fold : 

  • Improve the riding experience for the customer, by providing industry-leading products.
  • Communicate our tests and product review results directly with manufacturers, in hopes of product update revisions.
  • Share the information gained, with the cycling community.


If you have taken a moment to sit down and think about just how many versions of fat bike suspension forks are out there, it's over 20 makes/ let the selection process begin !!




  • Versions (4) : RL 100/120, RCT3 100/120
  • Travel : 100mm, 120mm
  • Hub Compatibility : 150mm thru-axle standard hub only (5x150 TA)
  • Steerer : Tapered head-tube only
  • Tire Compatibility : 26 x 4.8" and 27.5 x 3.8" 
  • Suspension : Solo Air Spring w/ RCT3 Damper
  • Lockout control : Yes. Full lockout




  • Versions (1): Carbonara
  • Travel : 60mm max, C.O.R. approx. 15mm (constant operating range of travel at speed)
  • Hub Compatibility : 150mm thru-axle standard hub only (5x150 TA)
  • Steerer : Tapered head-tube only
  • Tire Compatibility : 26 x 4.8" and 27.5 x 4.5" and 29 x 3.0"
  • Suspension : Carbon Leaf Spring, no damping / no rebound control
  • Lockout control : None
Wren Logo


  • Versions (5): ATK 110, ATK 150 w/Keyed Stanchions, WSF-135/AS or /AT, WSF-150/AS
  • Travel : 80, 90, 100, 110, 120, 130, 140, 150mm
  • Hub Compatibility : 135mm or 150mm thru-axle standard hub
  • Steerer : Straight or Tapered head-tube
  • Tire Compatibility : 26 x 4.8" and 27.5 x 4.5" 
  • Suspension : Twin-Air System w/Damper
  • Lockout control : Yes. Full lockout
Manitou Mastodon


  • Versions (9) : MASTODON COMP STD 100/120 and EXT 100/120, PRO STD 100/120 and EXT 100/120/150
  • Travel : 80, 100, 120, 140, 150mm
  • Hub Compatibility : 150mm thru-axle standard hub only (5x150 TA)
  • Steerer : Tapered head-tube only
  • Tire Compatibility : STD = 26 x 4.0 and 27.5 x 3.8 , EXT = 26 x 4.8" and 27.5 x 4.5" 
  • Suspension : Dorado Air w/ MC2 Damper
  • Lockout control : Partial lockout only


  • Versions (1) : OLAF PBR 100
  • Travel : 100mm
  • Hub Compatibility : LEFTY proprietary 73mm hub only
  • Steerer : Tapered head-tube only
  • Tire Compatibility : 26 x 4.8" and 27.5 x 3.8"(?) 
  • Suspension : 2Spring Air w/ PBR Isolated Damper Tech and Enduro+ Tune
  • Lockout control : Yes. Full lockout


First - we have to determine a number of factors that will go into this test.  This criteria selection process needs to be fair, and the eligible product options need to be up to date with 2018 production standards and readily available in the marketplace.  In addition, we need to baseline them in several ways, so that cross-platform testing can be done, where we are not randomly picking suspension forks by different vendors in random travel lengths and AC Heights.  This all needs to be standardized through baseline criteria.  Next, we have to establish, what product we are going to consider the "baseline" by which all others will be compared to.  We need to do all that, and make sure the test bikes can accommodate those forks too, without any modifications needed to the installation (such as crown race extenders) and no conflicts with wider fork crowns hitting the down-tubes, when extended in a 90-degree turn from the centerline.

Once we determine which brands, or product lines we will test, we need to find the ACTUAL suspension fork, in EACH of those product lines that best meets the baseline criteria.  As mentioned above, there are over 20 suspension forks to currently chose from.  We need to narrow that down to 3 forks.

In Short, here is the BASELINE TEST Criteria REQUIREMENTS :

  • Establish a baseline suspension fork by which all others will be compared to
  • Establish the other two suspension fork manufacturers in the competition, based upon a set of defined Industry requirements.
  • Establish a Cross-Platform requirement (Axle-to-Crown AC Height) each suspension fork needs to meet, in order to select that particular model from all available manufacturer's options
  • Establish the test bikes, which have 100% full compatibility with all 3 suspension forks selected
  • Install and configure the suspension forks on the test bike(s), and perform the test



We had to look at all the suspension fork manufacturers, and choose the 3 brands that best met the acceptance of mass production standards, features and suspension travel, for all fat bikes in 2018.  From those 3 manufacturers, we selected the best forks they had to offer, in their premium build lines, and installed them on industry-leading alloy and carbon fat bikes.


  •  The suspension forks in this review need to be leaders in their class, for their prospective manufacturers.
  •  The suspension forks need to have at least 100mm of true travel, with full Damping capability.  (this omits Lauf Carbonara, as it is only a leaf spring fork, with limited travel and has a very fast rebound, which cannot be controlled or dampened.)
  • The suspension forks in this review needed to accommodate tires up to 26 x 4.8" in size on 80mm rims. (according to published Manitou fitment charts, this would omit the Mastodon PRO STD series) 
  • The suspension forks need to accommodate a standard 150mm wide front hub with a 15x150mm thru-axle.  (Even though it is a well-performing fork, this omits the Lefty Olaf, which uses a proprietary hub system that has not gained mass acceptance, and is limited to specific frames and wheelsets designed/compatible for its specific use.) (This also omits the 135mm hub versions of the Wren Twin-Air series.)
  • The suspension forks need to have tapered head-tubes. (This omits the Wren WSF135 and WSF150 100mm travel forks, that have straight steerers for non-tapered headsets.)
  • The suspension forks need to have either a Full or Modified lockout control.  (This would again omit the Lauf Carbonara.)
  •  The suspension forks in this review need to have the SAME or VERY SIMILAR axle-to-crown (AC) heights.  Why?  Because AC Height determines how high the bike cockpit sits off the ground, and if the AC height is altered, so would the overall geometry of the entire bike.  By keeping the AC HEIGHT the SAME for ALL suspension forks tested, we can then say the "bike itself" (meaning its unaltered geometry) will handle the "same" under all conditions, and the actual changes in ride quality and handling, will be DIRECTLY related to the installed fork's performance capabilities.
  • We then picked the best forks remaining, from each of the 3 leading manufacturers, with the AC HEIGHT = 530 +/- 1mm.
  • The modified AC Height after applying the Factory-suggested SAG setting, must be equal to, or less than =< 511mm AC HEIGHT.  This requirement is needed, because many Fat Bike frames have a "511" cut-off on their warranties and suspension-corrected geometries.


    • AC HEIGHT = 531mm
    • TRAVEL = 120mm
  • WREN ATK 110
    • AC HEIGHT = 530mm
    • TRAVEL = 110mm
    • AC HEIGHT = 531mm
    • TRAVEL = 100mm


  • 15 x 150mm Thru-Axle
  • Accommodates standard 150mm front hubs
  • Suspension travel of at least 100mm
  • Accommodates 26 x 4.8" tires (or larger)
  • Adjustable Damping capability
  • Adjustable Rebound control
  • Full or Modified Lockout switch
  • Tapered headtube design
  • Factory-suggested SAG adjustment results in AC =< 511mm



Often overlooked, and not always understood, is the AC HEIGHT specification of a fat bike frame.  This Axle-to-Crown (AC) measurement is a very important specification, because manufacturers often base their warranties and frame durability ratings off that number.  This is also closely tied to the "Suspension Correct" calibration number assigned to manufactured frames. 

From our extensive research done on STACK and REACH (click for separate article review), our internal database found that the majority of quality hard tail fat bike frames, are suspension corrected to an Axle-to-Crown (AC) Height of 511mm. 

If you try to install a suspension fork that exceeds this number - and your frame is rated to MAX AC=511, you are liable to :

  • void your frame warranty
  • increase the ride height of the front end of the bike
  • degrade the intended ride-quality, by altering the intended geometry of the bike
  • potentially throw off the center of gravity


The suspension fork shootout takes all the above facts and variables into consideration and has carefully prepared their fork selection, so that after applying the manufacturer-suggested amount of SAG to the fork, the final ready-to-ride AC Height will be <= 511mm.

NOTE : After applying factory-suggested SAG settings the available Travel is also reduced.


TRAVEL and AC HEIGHT Adjusted for SAG :


  • SAG setting = 20%
  • Travel = 96mm
  • AC Height = 507mm


  • SAG setting = 20%
  • Travel = 88mm
  • AC Height = 508mm


  • SAG setting = 22%
  • Travel = 78mm
  • AC Height = 509mm






Once the Suspension Forks for this test were selected, we then decided upon the best available fat bikes to perform the testing. 


  • The most important required qualification, was that each test bike would be 100% compatible with installation of all 3 forks without any aids or modifications needed to make them fit, (such as crown race extenders) nor could the installed forks interfere with the bikes' down tubes (when turned 90 degrees off the centerline) .
  • Each bike needed to have tapered head-tubes, and front wheelset hubs = 150mm, with 180mm Rotors (or larger), and use a 15mm Thru-Axle bolt.
  • Each fat bike needed to be All-Mountain (AM) rated, and ready to tackle the toughest local trails the testers could throw at it.
  • Each fat bike needed to have suspension corrected geometry (as discussed above) to accommodate these forks, and not void any manufacturer's warranties.
  • Each bike needed to be configured with excellent componentry, and ready for winter riding conditions.




  • 2016 FATBACK RHINO (XL) Lightweight Alloy Frame (w/adj rear chainstay dropouts)
  • SRAM XO1 11spd Drivetrain
  • SRAM GUIDE Hydraulic Brakes
  • SRAM 180FR/160RR Centerline Rotors
  • DT SWISS BR710 WHEELSET 82mm width (setup tubeless)
  • TERRENE WAZIA 26 x 4.6 Studded Tires
  • Total weight was 30 lbs w/ BLUTO RCT3 120 or 31 lbs w/ WREN ATK 110 or MASTODON PRO 100 suspension



(If the first bike ran into a limitation or "feature" on any fork, this secondary bike would be used to replicate and verify that condition, using the same type of fork, or same fork, as needed.

  • 2018 FATBACK CORVUS FLT (MD) Carbon Frame
  • SRAM XO1 EAGLE 12 SPD Drivetrain
  • RACEFACE NEXTR Carbon All-mountain/Enduro-rated Crank
  • SRAM GUIDE ULTIMATE Hydraulic Brakes
  • SRAM 180FR/160RR Centerline Rotors
  • DIRT COMPONENTS THUMPER WHEELSET Carbon 83mm width (setup tubeless)
  • SCHWALBE ADDIX JUMBO JIM 26 x 4.0 All-Season tires
  • Total weight of bike was 26 lbs w/ WREN ATK 110 or MASTODON PRO 100 suspension, and 25 lbs with the Bluto RCT3 120 installed.




FOES MUTZ150 - EAGLE 12spd

(used as a verification platform, when testers on the first two bikes found issues or limitations of their WREN ATK or MASTODON PRO EXT test forks.  This bike then tested that fork in the 150mm travel version only, to see if the issues/limitations persisted at that level too).

  • 2018 FOES MUTZ 150 (LG) Alloy Frame, Full-Suspension
  • SRAM XO1 EAGLE 12 SPD Drivetrain
  • SRAM GUIDE RSC Hydraulic Brakes
  • SRAM 200FR/180RR Centerline Rotors
  • DIRT COMPONENTS THUMPER WHEELSET Carbon 83mm width (setup tubeless)
  • MAXXIS MINIONS FBF4.8 Front and FBF 4.0 Rear EXO-TR-rated Tires
  • Total weight of bike was 36 lbs w/ WREN ATK 150 or MASTODON PRO EXT 150 suspension


All bikes pictured in this review were custom built by

All photographs, review content, and charts contained in this review are copyright 2018 of either or Ryan Ellis.


The Suspension Forks






The Suspension Forks















The Rockshox Bluto was the first suspension fork for fat bikes, entering the market in October 2013 and forever changed the way riders and manufacturers looked at fat bikes.  The Bluto ushered in many technology changes for fat bikes, and made the sport a better.  SRAM made two versions of the Bluto, the RL and the RCT3, in both 100mm and 120mm travel lengths.  We are testing their final version, the RCT3 120mm, w/ tapered steerer, and accepts up to 26 x 4.8" or 27.5 x 3.8" tires, on standard 150mm hubs.

BLUTO RCT3 - in the box

  • AC HEIGHT = 531mm
  • TRAVEL = 120mm

Inside the Retail Box :

  • 15 x 150mm MAXLE Lite Axle
  • Star Nut and basic service kit
  • Decal



The Wren Twin-Air suspension fork is an inverted design with keyed stanchions, and has gone through at least two major revision upgrades in the last 3 years.  This version has an adjustable rebound, compression, and air-side control, along with full lockout mode.  There are only two versions of this fork, and both use a tapered steerer.  The "110" covers travel increments of 80, 90, 100, and 110mm.   The "150" covers travel increments of 120, 130, 140, and 150mm.   Both accept up to 26 x 5.0" or 27.4 x 4.5" tires on most standard 150mm hubs.  We are testing the latest Twin-air version, in the 110mm travel length.  The model number is WSF150-110ATK.

WREN - in the box

  • AC HEIGHT = 530mm
  • TRAVEL = 110mm

Inside the Retail Box :

  • Carbon Bash guards and hardware
  • 15 x 150 Wren lightweight alloy bolt-on axle
  • Wren User manual
  • Cable Routing gear
  • Travel and AC Height clips



The Manitou Mastodon PRO is the newest fat bike suspension for on the market, and has been in use for about a year now.  This fork looks to improve on performance where the Bluto RCT3 left off and is claimed to be 25% stiffer.  It is the widest, tallest, and heaviest of the bunch, and comes in a bewildering selection of 8 different retail versions capable of 100, 120 or 140mm travel, plus 2 additional OEM versions with 150mm travel.  We are testing the MASTODON PRO EXT 100, with 100mm travel and accepts up to 26 x 5.0" tires.

MASTODON - in the box

  • AC HEIGHT = 531mm
  • TRAVEL = 100mm

In the Retail Box :

  • Stealth Gray Decal Set
  • User manual
  • Spacer/Token kit
  • TPC Rebound Damping, Hi+Lo Speed PRO Setup chart
  • IVA Token/Clip Adjustment chart
  • Travel Adjustment Token/Clip chart

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Beginning of Review





Beginning of Review






The Review

Author, Ryan Ellis

February 2018


"I need / want to purchase a (new) suspension fork for my fat bike, but what fork should I buy?"  It’s a common question but the answer is not as clear as I would like.  With limited information and reviews online about many of the new forks consumers are forced to roll the dice with a $1000.00 suspension fork purchase and hope they choose well. 


When I bought my fat bike one season ago the fork options were a rigid steel fork, a rigid carbon fork, or a RockShox Bluto.  The Lauf was also an option but for my trail riding and four season needs it offers little useable travel, no spring damping and just looks goofy to me.  I chose to go with a RockShox Bluto RL in 100mm of travel then changed it out for a Bluto RCT3 with 120mm of travel.   After about 8 months of riding on the 120mm travel RockShox Bluto RCT3 the fork developed a knocking sound that my mechanic attributed to bushing play.  The Bluto is going back to RockShox for warranty consideration and I’m going to take this opportunity to change it up for a different fork.

Thanks to in Burlington, Ontario I had the opportunity to perform an extended test ride with the top models from Wrensports and Hayes / Manitou

At the conclusion of the test period I will be putting my money where my mouth is an ordering a new fork from 

Here are my impressions, findings, and thoughts from behind the handlebars with the RockShox BLUTO RCT3, the WREN 110 ATK inverted fork and the Manitou MASTODON Pro Ext 100 - FAT BIKES in CANADA


I am neither a professional writer (you’ve probably already picked up on that) or the best fat biker out on the trails.  I’m the average 40-year-old weekend warrior who gets 1-2 good fat bike rides in per week during the winter.  I’m 6’3” and 200(ish) lbs and I am only a couple years into my fat bike riding career. 

Prior to fat bikes, I do have more than 20 years of off road riding experience and currently enjoy a mid travel, full suspension 29er for most warm weather riding.  My fat bike is primarily a winter ride and this review is based on testing during an Ontario winter with temperatures (usually) between +5 Celsius and -20 Celsius. 



This fork review was based on six weeks of regular riding on the same bike.  It required lots of late night fork swaps but it should provide a relevant comparison.  The test mule was an XL Fatback Rhino Alloy with a SRAM XO1 11 speed drive train, SRAM Guide hydraulic brakes, and DT Swiss BR 710 wheel set. 

Of particular note, this frame is a great platform for testing because it provides plenty of down tube clearance to accommodate all of the forks in this test.  Please keep in mind that your frame may not provide the same down tube clearance.


Keeping it scientific

This review took place on the trails and not in a laboratory.  My impressions are based only on my own observations and experiences riding each fork.  I did my best to subject each fork in a variety of trail conditions and environmental conditions. 

Temperatures during testing were generally cold in the -10 to -15 degrees Celsius range with a couple opportunities to ride each fork closer to the freezing mark. 

The trails were snow covered for most of the testing period. Although, I did manage to get one ride in on the new Mastodon Pro EXT 100 before the first snow of the season and one ride in on the Wren 110 ATK after a thaw and rain destroyed the snow cover. 

As noted above, the fat bike suspension forks were all tested on an Alloy XL Fatback Rhino frame and tire pressures were maintained in the range of 6-7psi in the rear and 7-8psi in the front tire." 

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Marketing information from the RockShox website

“We started with the features you’ve come to love from RockShox: Fast Black aluminum upper tubes, stout 15mm Maxle, remote or crown adjustable damping, tapered steerer tube, and the infinitely tunable Solo Air spring. Then, the chassis got the fat treatment by reengineering it to meet the unique needs of fat tires and wheels. Everything from crown, to arch, to axle has been optimized to tackle the increased torsional loads of its wide stance. With more traction and control than ever before, you’ll never be happier you went fat.”


RockShox Bluto RCT3 Specifications

The BLUTO is available in four (4) different versions.  

  • BLUTO RCT3 100, 120
  • BLUTO RL 100, 120

The ROCKSHOX BLUTO RCT3 120 is the fork selected for this test review, and is highlighted in green in the chart below.

BLUTO RCT3 Physical specifications and tire compatibility.




BLUTO RCT3 120 equipped Fatback Skookum

RockShox Bluto RCT3 First Impressions


(by Lead Independent Tester)

"Having owned and ridden numerous RockShox products over a number of years, I have always found their fit and finish to be excellent.  With the exceptions of a couple of very tiny paint imperfections, the fit and finish of the RockShox Bluto RCT3 was close to perfect." 


"All damper and rebound controls are easy to access and operate and the sag setting indicators on the stanchions are a touch that I really appreciate when setting up the fork.  The air pressure chart on the fork leg gets you into the ballpark quickly and it’s easy to add or remove a little air pressure to make your final adjustments."


"This particular fork has the bolt-on Maxel Lite15mm axle and after riding both the bolt-on and the quick release (QR) version, I would always choose the simplicity of the bolt on-axle.  Even when using a rack that required me to remove the front wheel I found the bolt-on Maxel Lite to be easier to use than the quick release axle." 


RockShox Bluto RCT3 Initial Setup


"The set up of the RockShox Bluto RCT3 was very quick and easy.  A pump up to the recommended air pressure and a couple small tweaks to set the sag was the bulk of the work.  Rebound was set with the garage floor bounce test and compression always run wide open.  I’m not one to fiddle with lock out switches and levers and would prefer some inefficiency in climbing, rather than futzing with my suspension fork.  I didn’t change this setup for the duration of my time with this fork." 


"If I had any volume reducing tokens I would have liked to try adding one or two to make the suspension a little more progressive but I didn’t have any on hand.  I’m also not sure how many tokens were pre-installed by the factory, so I can’t tell you how many I was riding during testing." [see footnote (*1*) below]


RockShox Bluto RCT3 Ride quality


"On the trail I was impressed with the RockShox Bluto RCT3.  I found it to be supple over small bumps but not quite as progressive over larger hits as I would have liked.  With 20% sag I would regularly use all 120mm of available travel and bottom out when riding moderate trails.  I never experienced a harsh bottom out but additional bottomless token may have provided a more progressive suspension feel." 

Bluto RCT3 120 equipped FATBACK RHINO XL XO1

"Ride quality did not noticeably change with temperature fluctuations and the fork performed well at -15 Celsius and at +30 Celsius.  I did not experience any of the temperature related issues such as leaking seals and stiffening damper with the RockShox Bluto RCT3 that I have read about in the online forums." 


"I’ve read reviews and watched YouTube videos about the RockShox  Bluto and the term “noodly” gets used a lot to describe the stiffness of the fork.  Because almost all of my fat bike riding experience has been on a Bluto equipped bike, I therefore couldn’t compare the Bluto to a stiff rigid fork.  When riding with the Bluto I did notice some handling characteristics of the bike that I initially attributed to fat tires and soft sidewall flex."


"After riding the Wren 110 ATK and the Mastodon Pro EXT 100 on the same bike, on the same trails, and with the same tires and tire pressure, I’m sure that the 32mm stanchion RockShox Bluto chassis was just overwhelmed and demonstrated enough flex to be noticeable in the handling of the bike."


"The 32mm stanchions on the Bluto look down right spindly (aka wimpy looking) installed on just about every fat bike out there.  I’m old and a chicken, so hucking off large drops with my fat bike is not in the cards.  The structural integrity of the Bluto was still in the back of my mind when making my line choices, because  I would avoid some of the drops and features that wouldn’t give me any concern when riding my 29er full suspension trail bike.  There are lots of videos online of great riders pushing their Blutos to the limit in demanding terrain, so I’m sure the fork is up for the challenge, but for me it just wasn’t confidence inspiring."    


BLUTO RCT3 120 equipped FATBACK RHINO XO1 build

"When reading about the Bluto online I found numerous complaints about the fork performance deteriorating when riding below freezing.  I didn’t experience this particular problem with the Rockshox Bluto RCT3 or with the RockShox Bluto RL under those conditions.  Rebound and compression speed may be slower in colder temperatures but not enough that I found it noticeable on the trails."


"The flex of the fork identified above could be considered a problem, but the fork is essentially a widened cross country chassis.  It doesn’t pretend to be anything else and does offer the lightest weight of the bunch (3.7 lbs).  If you want a lightweight fork offering this much travel, some flex is the compromise you need to be willing to accept."


"The major issue that I experienced with the RockShox Bluto RCT3 is a knocking sound and play that developed inside the fork that has been attributed to worn bushings.  This has occurred with less than a year of seasonal riding on the fork.  This disappointed me after spending quite a bit of money on the RockShox Bluto RCT3, but I was willing to do the maintenance to get myself riding again.  Unfortunately, with the RockShox Bluto the bushings are not a simple maintenance item.  To replace the bushings you need to replace the entire fork lowers.  This seems like a lot of waste and expense and hassle to perform a common repair.  A quick search of the usual online retailers revealed new lowers without stickers for approximately $300.00.  A new sticker kit will add another $50.00 to the cost, totaling $350.00 in repairs."


(*1*) - (Tokens) : The BLUTO RTC3 120 has the ability to add up to 4 tokens, and zero are pre-installed at the factory, in this configuration.







Marketing information from the Wren Sports website:

“The Inverted fork design simply works better. By inverting the fork so that the lighter stanchions are on the bottom, we reduce the mass of the moving part of the fork so that it will react quicker and easier to the trail. Inverting also anchors the stanchions into the stronger, larger upper tubes and crown making the overall chassis much stronger and stiffer. It also lowers the fulcrum point where the uppers join the stanchions compared to other fork designs decreasing the leverage factor. Inverting also positions the seals downward so that all kinds of bad stuff doesn't sit on them and get pulled into your fork.”


Wren 110 ATK Specifications

The Wren inverted fat bike suspension fork comes in two versions :

  • WREN ATK 110, 150mm     

[see footnote (*1*) below]

You can adjust Travel only or Travel and AC together, on these models. The Wren 150 ATK version weighs about 100g more at 2208g. 

The WREN ATK 110 was the suspension fork selection for this review test, and is highlighted in Green, in the charts below :





Wren 110 ATK Inverted Fork First Impressions


(By Lead Independent Tester)

"If I can believe what I’ve found on the net, the WrenSports inverted fat bike suspension fork is an evolution of the “Fork of Many Names” that was previously branded and sold under multiple brand and model names.  My understanding is that WrenSports has undertaken a considerable redesign of the fork and the current iteration can’t really be compared to its predecessors." (*2*)


"Before this opportunity to test the Wren 110 ATK, I had never seen a WrenSports inverted fork in person and only had limited anecdotal information from riders who had.  I honestly didn’t have the highest expectations of the Wren and anticipated a prototype look and feel." 


"Upon opening the plainly packaged Wren I was surprised with the high quality feel and look of the fork.  It was slightly less refined than the RockShox Bluto RCT3 or Manitou Mastodon Pro EXT 100.  There are a couple sharp edges on the drop out casting, and the clamps that hold the stanchion guards on are a bit utilitarian.  Overall, this fork feels like a solidly built and high quality suspension fork.  Plus, it looks very cool!"

Wren ATK 110 Initial Setup

FOES MUTZ150 w/ WREN ATK 150 and FOX FLOAT DPX2 suspension - Custom Built by

"After reading the manual in its entirety a few times to make sure I fully understood the twin air system, setting up the Wren to the recommended starting point proved to be fairly straight forward, save for a couple minor challenges." 


"Step one is adding air to the top and bottom chambers equally until the recommended 20% sag is achieved.  With the inverted Wren fork design, you can’t simply use your shock pumps pressure gauge when pumping up the top and bottom air chambers.  Because of the floating piston design of the twin air Wren, the air pressure in the top and bottom chambers will always equalize.  The equalized pressure is relevant because the pressure inside the air spring provides the correct sag and can be adjusted to control bottoming out or to allow the fork to achieve full travel.  However, what is also important with the Wren’s twin air design is the relative air volume in the top and bottom chambers." 


"When setting up the fork initially Wren recommends that you add the same volume of air in both chambers to provide a very neutral starting point for adjustment.  The only way to do this is to count the number of pump strokes and add the same number of strokes to each chamber.  If the sag is more than 20% you can add a couple pump strokes to the top and the bottom and try again.  If the sag is less than 20% and you have too much air in each chamber the only option is to bleed all the air from the fork and start again.  The inability to make small, accurate, and recordable decreases in air volume without fully bleeding the air out of the fork is a limitation of the twin air design." (*3*)

Mid-summer 2017 Custom built Fatback Corvus testing the WREN ATK 110 in 90F temps.

"Once the sag is set and the fork has equal air volume (and pressure by default) in both the top and bottom chambers of the fork it’s time to adjust the rebound.  Wren has not provided detents or clicks to help you nor have they limited the range of adjustment that the user has access to.  The red adjuster knob on the bottom of the right fork leg provides complete adjustability to go from pogo stick fast to molasses slow, and everything in between.  It’s up to the user to select a speed that won’t allow the fork to pack up in the smallest bumps or eject them from the bike in larger bumps.  With very little rebound damping (fast rebound speed) there is a noticeable top out clunk sound inside the fork.  With a little more rebound damping dialed in, this sound completely disappears.  With higher speed riding or more frequent hits it may not be possible to run the rebound fast enough and avoid the top out sound." 


"With the sag set and rebound dialed I hit the trail and fine-tune the feel of the Wren.  By increasing the volume of air in the top chamber relative to the bottom chamber the Wren 110 ATK will provide a softer, plusher and less progressive ride.  And by decreasing the air in the top chamber relative to the bottom chamber the Wren will provide a more progressive feel.  Decreasing the volume of the top chamber relative to the bottom chamber is similar to adding bottomless tokens to a RockShox fork or adjusting the IVA system on a Manitou fork but the twin air design allows you to achieve the same affect by only your shock pump and without opening up the fork.  What can become confusing when making these adjustments is that the equalized air pressure in the top and bottom chambers will be influenced by adjusting the volumes of the upper and lower chambers and adjustments may have to be made to the sag.  For example if you adjust the fork to your preferred sag setting but then decide you want a more progressive ride characteristic and add some air to the bottom of the fork you may also notice that your sag is now less than 20%.  It can become slightly confusing!  Once you have settled on an air pressure that provides 20% sag and the volume ratio that you like you will want to record this so that you can achieve the same result in the event that you bleed the air completely from the fork and start from scratch." 


One of the Independent Tester's Fat Bikes - custom built by

"The Wren 110 ATK that I was provided for testing came with a quick release axle and a bolt on axle.  The design of each axle doesn’t feel as refined or sophisticated as the Axle system of the RockShox Maxle Lite or Manitou Hexlock SL but both do the job of holding the front wheel in place.  Wren recommends the bolt on axel over the quick release axle for all fat bike applications.  The bolt on axle provides more clamping force and rigidity to handle the forces generated by fat bike wheels." (*4*)


"The brake line management system on the inverted Wren is also different than a conventional fork.  If you fix the brake line to the fork leg, the inverted design results in a loop of brake line close to the rotor growing as the fork compresses.  The loop of brake line could find its way into the spokes or brake rotor.  Wren ships with two cable management guides that are fixed to the upper stanchion with zip ties.  These are essentially the same solution that is used with some externally routed dropper seat posts.  This solution is not as tidy as the brake line management found on a conventional fork but it is completely effective and it does allow you to control placement of the guides to avoid brake line rub."

Wren 110 ATK Riding Impressions

RAF RIDER testing the WREN ATK 150

"Riding the Wren felt very much like riding any other high-end bicycle suspension fork.  When tuned properly it provides excellent small bump sensitivity with the desired amount of ramp up as the fork progresses through its travel.  Steering was precise and noticeably faster than the RockShox Bluto RCT3 or the Manitou Mastodon Pro EXT 100." 


"I suspect the fast steering can be mostly attributed to the 45mm offset of the Wren vs. the 51mm offset of the Bluto and the Mastodon." 


"It is possible that the rigidity of the fork also enhances the faster steering response.  This is a very rigid fork - the most rigid of the bunch in my opinion." (*5*)


"During testing the effects of the fluctuating temperatures on the fork were a little frustrating as I tried to dial in the ride quality that I wanted.  As the temperature fluctuated (below the freezing point) so did compression and rebound speed.  Physics and the properties of air, oil and metal indicate that this effect should be noticeable on all suspension forks.  The Wren 110 ATK is the only fork that I’ve found it to be significant." (*6*)

Wren 110 ATK Issues


"Prior to riding the unique Wren 110 ATK I spent a few evenings scouring the Internet looking for whatever complaints I could find.  I wanted to know what to watch out for when testing the fork.  The two most common complaints that I could find were the fork “freezing up” in cold conditions, and rubbing of the tire on the upper fork leg.  The rubbing was attributed to the inverted design that allows some independent movement of each fork leg.  Interestingly, I didn’t find complaints about the Wren being more complicated to set up."  (*6*)


"In my experience during testing the Wren was absolutely influenced by cold temperatures."  (*6*)  "As ambient temperatures decreased from 21 degrees in my work shop to -10 degrees at the trail head the Wren’s rebound and compression damping both became much heavier during the parking lot bounce test.  The difference was more pronounced with rebound than compression.  During actual riding and at about -10 and warmer, the increased rebound damping and compression damping effect was minimized as the cycling suspension generated heat.  Rebound speed could also easily be increased to overcome the sluggish damper.  At temperatures colder than about -10 Celsius the Wren did not generate enough heat to overcome the effects of temperature and the fork in the fully open compression setting felt almost the same as it did with the lock out engaged.  This effect was more noticeable in riding conditions with a significant wind chill."   


"While the early heavy snow falls this season quickly smoothed out the most demanding terrain I did my best to hit every rock, log, jump, and trail feature that I could during testing.  Despite my best efforts, I was unable to duplicate any of the tire on upper fork leg rubbing that I’d read about online.  It’s possible tire rub is only noticeable with the widest of wide tires.  I have plenty of clearance with my 4.6” tires and the independent movement of the fork stanchions would have to be significant to ever result in rubbing.  The owners who reported rubbing may have been using the quick release axle and not the bolt-on axle, or, may have used the quick release axle installed incorrectly." (*4*)


FOOTNOTES (WREN ATK 110 section) - from the Manufacturer and

(*1*) - Response from : (True Fork Travel) -  I bet almost no one realized this, but the WREN ATK 110 is really a 120mm travel fork, and the WREN ATK 150 is really a 160mm travel fork.  They both sacrifice 10mm of usable travel, when the carbon bash guard clips are installed.

(*2*) - Response from : ("Fork of Many Names") - Previously marketed under the "Carver", "AEKO", "Muru" and "11nine" labels, and currently marketed under the "FATLAB" and "WREN" label.

(*3*) - Response from Wren : (Setting up Sag / Twin-Air Chambers) - "In terms of adding air to achieve sag, after initial setup and getting close to sag, we recommend small additions, not a couple of pumps at a time.  Each pump stroke can make a significant change, as you are getting closer and closer to dialing in the fork.  This would prevent having to start over. Yes, if you bleed there is no way to gauge accurately, but the advantages to the adjustability outweigh this in our opinion. We discussed this with our engineers during development, and the additional cost to equip the fork with digital gauges indicating where the sliding piston is located, was too expensive an option."

(*4*) - Response from WrenSports : (Axle Setup / Tire Rub) - "The QR and/or the Bolt-on axle should always be inserted first into the BRAKE side.  The securing bolt should then be fastened (firmly and to torque spec) via the drive-side of the fork." 

"Regarding tire rub - We have found that in those cases where we were contacted by customers about this issue, either the axle was installed backwards (not from brake side), or the two stanchions were not lined up evenly to allow the axle to slide in and seat evenly, which resulted in a loose condition that was not felt until riding.  This caused the wheel/rim to deflect into the left upper stanchion of the fork."

(*5*) - Response from WrenSports : (Regarding Steering Response) - "The faster, more precise steering is mostly due to the rigidity. The 45mm offset does also make some difference. The main reason for the picking 45mm as the offset, is to allow the fork to fit more bikes with varied geometry and help balance the ride. We did not work with just one OEM in mind. The offset also matches well with our AC adjustability to be able to put our fork on much older bikes."

(*6*) - Response from WrenSports : (Cold Weather Performance) - "We have discussed this at length with everyone involved.  We know there are Wren fork-equipped bikes out there that work great in temps much colder than the Bluto or the Mastodon can achieve (past -30c). We need to figure out why the particular test forks in this review did not perform for you." 

(*6*) - Response from : (Cold Weather Performance) - The failure of the Wren suspension forks freezing up prematurely between -5c and -10c has been verified by :

  • testing random sample forks from our own inventory, in both 110 and 150mm lengths.  These forks were shipped to us at different times in 2017, mostly between the end of the summer, into the winter months.
  • Customers out in the field have sent us communications indicating that some of their suspension forks froze up between -5c and -10c, while a few others stated their Wren forks worked down to -18c to -20c without a problem.
  • We crossed checked these findings by serial number, and found they were occurring in clusters.
  • Warranty replacement forks sent directly from the factory to customers in Canada, also exhibited premature freeze-up issues.

This indicates it is not an isolated incident, but instead a manufacturing inconsistency where build specifications have differed from real-world testing on forks built throughout 2017.   If the Wren fork was made in 2016, it appears to be more predictable and consistent than Wren forks made within the last 6-9 months.  We had perfectly working Wren forks in early 2017, but not by end of 2017.  Customers were starting to notice cosmetic and functional defects in the forks, by Fall 2017.  We immediately notified WrenSports LLC of these issues so they could investigate.

(*6*) - Response from WrenSports : (Cold Weather Performance) - "The updated (1 MAR 2018) factory specification of the Wren fork is to function problem-free down to -15c."

(*6*) - Response from : (Cold Weather Performance) -  Upon learning of our test results, WrenSports LLC asked for extra time to send out a new fork from the factory to beat/challenge the poor cold weather performance we were seeing in the forks we randomly pulled from current production runs.  We waited almost 3 weeks.  No fork arrived.  As of publication date [5 MAR 2018] we still do not have a clear answer as to what is causing this problem.  The review continues on...








Marketing information from the Manitou website:


“Real-world trail suspension for your fatbike! All-temperature performance soaks up chatter and big hits on freezing cold snow as well as it does on shimmering hot sand, and everywhere in-between.

  • Extended ride height versions fit up to 26×5.15” / 27.5×4.5” tires
  • Standard ride height versions fit up to 26×4” / 27.5×3.8” tires
  • All-temperature performance born of frigid winter ride-testing (certified to 0F or -18C)
  • 34mm trail chassis is stiffer and steers more precisely than any other fatbike suspension fork
  • E-MTB Certified”


Manitou Mastodon Pro EXT 100 Specifications

The Manitou Mastodon is available in nine (9) different versions!  There are the PRO (Durado Air) and COMP (Expert Air) model lines, divided into STD (standard) and EXT (extended) Ride Height configurations.  Eight (8) of these models are Retail, while one (1) version is OEM only.

  • MASTODON PRO EXT 150 - (OEM only)
  • MASTODON PRO EXT 100, 120
  • MASTODON PRO STD 100, 120
  • MASTODON COMP EXT 100, 120
  • MASTODON COMP STD 100, 120

The MANITOU MASTODON PRO EXT 100 is the suspension fork selection for this test review, and highlighed in green, in the charts below.





Mastodon Pro EXT 100 First Impressions

(by Ryan Ellis, Lead Independent Tester)

"The Manitou Mastodon Pro is the biggest, widest and heaviest fork of the bunch.  It looks solid, it feels solid and the build quality is excellent. 

  • The fit and finish of this fork is exceptional, the best of the test group. 
  • Machining and anodizing are perfect. 
  • With 34mm stanchions, a wide stance, and cool reverse arch design the Mastodon Pro looks like it belongs on a fat bike. 
  • The bolt on hex style axle of the Mastodon is an exquisite piece of design and machining that is far more sophisticated than the axle found on the Wren ATK or the Bluto RCT3
  • The Mastodon Pro provides two locations on the left fork leg that the brake line can be easily attached via zip ties.  This is not as neat as the built in clamp on the Bluto but it is quite a leap ahead of the primitive cable guides that come with the Wren." 

Mastodon Pro EXT 100 Initial Setup


"The Mastodon pro features a solo air style air spring as well as externally adjustable rebound damping, high speed compression and low speed compression via the standard anodized knobs on the top and bottom of the damper leg of the fork.  Additionally the Mastodon pro offers the IVA (incremental volume adjust) system in the air spring leg of the fork.  The IVA system is clever in that it doesn’t require any additional parts like the RockShox bottomless token system.  After opening the air spring side of the fork with a 24mm socket the air spring position can be adjusted with a series of built in clips.  Reducing the volume of the air spring with provide a more progressive ride that ramps up quicker to reduce bottoming.  Increasing the volume of the air spring will provide a more linear ride that bottoms easier but provides a supple ride that is sensitive to small bumps throughout the stroke of the fork.  During testing I rode with the IVA system at the factory settings and found it to be sufficient for riding snow covered trails, only bottoming out gently a couple of times.  During more aggressive summer riding a slightly more progressive tune would probably be in order."


"Manitou provides an easy to read single page setup guide for the Mastodon Pro and I found the recommended settings to be a great starting place.  For my weight around 100psi is recommended to achieve static sag in the 15-25% range.  I settled on approximately 25% sag for myself.  I adjusted the rebound speed to my liking and left high speed and low speed compression wide open." 


"The only setup annoyance that I had when installing the Mastodon Pro was related to brake line routing.  I found that the reverse arch and the placement of the brake housing attachment points on the rear of the leg resulted in some unusual routing of the brake line through the fork between the crown and the arch to minimize brake housing rub points on the fork and on my frame.  My best solution still required me to protect the fork at two locations with tape.  Brake line routing may be cleaner with your setup." 

Mastodon Pro EXT 100 Riding Impressions

"The Mastodon Pro EXT 100 uses Manitou’s Dorado Air spring and top of the line MC2 compression damper.  When combined with the stiff chassis of the Mastodon Pro the ride quality is as good as you would expect from any of the best mountain bike suspension forks on the market.  The fork performed well in all conditions and felt very composed and not in any way challenged by the terrain.  There is some noticeable stiction with the Mastodon that is more evident during the workshop bounce test than it is out on the trail.  It is possible that this will improve but is still noticeable after 5-6 hours of riding." 


"During testing of this fork I did not experience any noticeable influence of cold weather on the performance of the fork (within 5 Celsius to – 15 Celsius).  The fork behaved in sub-zero temperatures just as it did when I set it up in my warm basement workshop." (*1*)


Mastodon Pro EXT 100 Issues

"The Manitou Mastodon was only recently released and I wasn’t able to find much information about the fork.  The online forums were buzzing with anticipation of this new fork but I didn’t find any complaints.  During my testing I identified a couple of small issues that a potential buyer should consider before purchasing."

SIZE - "Firstly, the Mastodon Pro is a huge fork with a very wide stance and an equally wide crown.  The fork is so big that I suspect that the crown will not clear the down tube and may result in crash damage to the frame or the fork if installed on some fat bikes.  Even many frames that were designed for use with a Bluto don’t always provide the down tube clearance required to use a Mastodon.   The high speed and low speed compression knobs are also elevated above the right fork leg which will further exacerbate the problem for frames with already tight clearance.  Anyone interested in the Mastodon should check for potential clearance issues if this is a concern." (*2*)


AC Axle-to-Crown Height - "Secondly, for the same 530-531mm axle to crown measurement and a few hundred grams more weight the Mastodon Pro provides only 100mm of travel (with the extended height fork tested) vs the 110mm of travel offered by the Wren 110 ATK vs. the 120mm of travel of the RockShox Bluto RCT3.  I suspect that the Mastodon is short changing us on travel to accommodate the 27.5 x 4.5” fat tires found on the bikes of major OEM purchaser Trek." (*3*) 


WEIGHT - "Up to half a pound more than a Wren and 1.2 lbs more than a Bluto" (*4*)



(*1*) - (Cold Weather Testing) - We completely agree.  The Mastodon PRO EXT fork worked well down to its rated -18c without any problems, and continued working well down to -20c.  Extended time outside, or in the wind, did get it to start acting sluggish as you went past -15c.  It performed the best of all 3 forks tested in cold weather.

(*2*) - (Size) - This is a big fork!  (Hence, I think, the reference to a Mastodon in the wild).  This fork does have compatibility issues on older style frames, that were built with only the Bluto in mind.  I think as time passes, frames (specifically down-tube shapes) will be updated, to accommodate this wider stance.  The Mastodon is 23mm, or about 1 inch WIDER than a Bluto.  Lucky for us, the MASTODON PRO and WREN ATK both fit perfectly on all the FATBACK and FOES RACING fat bikes we custom build. 

(*3*) - (AC Axle-to-Crown Height) - OK, this one is frustrating.  For two reasons.  There are so many fork versions to choose from, plus, you need to second guess the charts that Manitou released.  It seems that they did not test every tire combination with standard 80mm rims. Some tires rated as not being compatible with the STD version actually DO fit.  This "error"  or miscalculation causes customers to play it safe and go for the EXT version, versus the STD version.  What that does is add 20mm to the AC Height, slackens out the frame geometry, and reduces the travel by 20mm.  This gives the Mastodon the worst AC-to-suspension-travel ratio of the forks tested.  If Manitou invests some time updating their charts on this rating... they might help customers gain 20mm of travel, for the same AC stack height, or, help them save 20mm of AC stack height, for the same travel rating.  (Please refer to our charts at the beginning of the review for more info on general STD vs EXT stack and travel).

(*4*) - (Weight) - As a point of reference, for the weight weenies out there sifting through manufacturer's claimed weights -  Here are some actual digital measurements, from the Park Tools digital scale in our workshop.  The weights are "race-ready", meaning they include the axles, cut steerer tubes (230mm usable), star nuts installed, and in the case of the Wren, the carbon bash guards installed:


  • 4 lbs 14 oz
  • 2.23 kg

WREN ATK 110    (-0.2 lbs lighter)

  • 4 lbs 11 oz
  • 2.15 kg

BLUTO RCT3 120    (1.0 lbs lighter)

  • 3 lbs 14 oz
  • 1.77 kg













Which fat bike suspension fork is the best?


"If you’ve read this far or even scrolled to the end of this article you would probably like to know what fork I think is the best.  Before we go any further let me remind you that what went into this article was not scientific testing.  The observations and reports are based on one rider’s experience over an extended test ride in a variety of trail and environmental conditions.  To be honest, I was expecting to be able to recommend a clear winner but these are all good forks.  Each of these fat bike suspension forks has both strengths and weaknesses vs. their competition."






  • The lightest weight option (3.9 lbs uncut)
  • Good cold weather performance (tested to -18c) without modifications or aftermarket seals
  • Most likely to be compatible with your frame
  • Great value when buying with a new bike
  • Good suspension performance with easy setup
  • Air pressure guide and sag settings printed on the fork
  • Maxel Lite Axles are one very simple and easy to use
  • Fit and finish of the fork is excellent
  • Built in brake line management clamp is built into the fork
  • The most Travel for the same AC Height (120mm for 531mm AC)
  • 2 year warranty


  • More flex than the Wren or the Mastodon
  • Questionable reliability
  • Steering is not as precise as the Wren or Mastodon, likely due to fork chassis flex
  • Only available with lower level damper technology
  • Replacing bushings requires replacing the fork lowers
  • Looks spindly next to fat bike tires


Choose the BLUTO RCT3 fork if :

You are buying a new fat bike and it comes with a RockShox Bluto or you can upgrade to a Bluto for very little money.  This suspension fork offers good performance at a relatively light weight and it will make your fat bike a versatile four season machine that is a lot more fun to ride than a rigid fat bike.



  • The most rigid fork in the test
  • Quick and precise steering
  • Modular fork is easy to maintain and spare parts are usually readily available
  • The user can communicate directly with the manufacturer for parts and support
  • Lighter weight than the Mastodon with slightly better down tube clearance
  • Excellent suspension performance
  • Unique fork from a small manufacturer
  • Only two models provide all travel and tire compatibility options
  • 2 year warranty

WREN ATK 110 and 150


  • More time consuming to initially setup and dial in
  • The most expensive fork in the test
  • No built in air pressure charts or setup guides
  • Top-out “clunk” when running fast rebound speeds
  • Less Damper Tuning options than the Mastodon Pro
  • Regular stock fork damper freezes up between -8c and -10 Celsius
  • Purchase of an additional damper required for cold weather compatibility adds $100.00+ to the cost of the fork
  • Carbon stanchion "bash" guards prone to getting caught on vehicle interior, bike rack, etc. and are prone to breaking
  • Installing the Carbon Bash Guards reduces 10mm of usable travel on all Wren forks
  • Decent fit and finish, but not nearly as good Manitou and RockShox
  • Bolt-on and quick release axle designs are much less refined than the Bluto or Mastodon axles. 
  • Brake line routing relies on plastic guides zip-tied to the upper fork leg
  • Unique fork from a small manufacturer

Choose the Wren 110 ATK (or 150 ATK) if:

  • You ride mostly in temperatures above -10 Celsius and you want the most rigid and precise steering fat bike suspension fork. 
  • You enjoy tinkering with the tuning of your suspension fork to get just the right feel.  
  • You value ease of repair and maintenance and appreciate the modular design of the Wren that allows the user to easily replace damaged or worn or lost components. 
  • You are looking for an alternative to the to Bluto that offers better handling and a more robust design but is still compatible with your frame without clearance issues. 



  • Quick and easy to setup
  • Aftermarket forks come with two sets of decals to customize the look
  • The best Fit, Finish, and Build Quality of the three forks tested
  • Superior Axle Design of the 3 forks tested
  • Cold Weather Performance tested down to -18c right out of the box, with no additional parts to buy, modify, or install.
  • The Most Tunable Damper with High Speed, Low Speed, and Rebound Adjustment
  • Very composed and refined ride feel through all conditions
  • IVA air spring volume adjuster requires tools but no additional parts
  • Manitou has around 30 years of mountain bike suspension fork knowledge and experience


MASTODON PRO EXT 100 and 150


  • The heaviest fork in the test (4.7-4.9 lbs)
  • Confusing array of (8) different RETAIL Travel and AC fork Height (STD vs. EXT) variations to choose from - (Tire height and width is the determining factor between STD vs EXT, and some posted MANITOU charts are inaccurate)
  • Slightly more chassis flex than the Wren (but significantly less flex than the Bluto)
  • Extra wide crown will have clearance issues with some frames  (1 inch wider than a Bluto)
  • The lowest travel option for the same Axle-to-Crown (AC) Height on the PRO model
  • 1 year warranty




Choose the Manitou Mastodon Pro (EXT and STD in all travel variations) if:

  • You appreciate good suspension performance but prefer to set up your suspension fork once and have it perform across a wide variety of conditions. 
  • You like to tinker with your bike but you’re more inclined to have your suspension fork serviced by a shop as required.  
  • Your frame has clearance for the wide Mastodon crown and you don’t mind less suspension travel and more weight for the same axle to crown height, when picking the PRO EXT model.  (STD model has lower AC, but accepts only narrower tires)   
  • Seeing the name of a major suspension fork manufacturer on your fork leg is comforting. 
  • You appreciate the best build quality, fit and finish of the bunch.


And the Winner is....

3 mastodons - 1500-wm.jpg





"Thank you again to for the opportunity to participate in this extended test ride of the best fat bike suspension forks currently available.  Even after multiple test rides with each fork choosing between the Wren and the Mastodon to replace my Bluto was not easy." 


Final thoughts about the Wren 110 ATK

"The Wren was a lot of fun to ride, when it worked.  The burly 43mm uppers and 36mm stanchions inspired confidence and encouraged me to ride features that I have previously avoided on my fat bike.  I like the idea of supporting a small company like Wren Sports and the ability to easily contact customer service for parts and support is a significant benefit of riding the Wren. 

The major downside of the Wren is poor cold weather performance.  All of the three Wren forks used during testing suffered from the same heavy damping and rebound as the temperatures dipped below O degrees Celsius. 

By -10 degrees Celsius each test fork stopped operating altogether, even with the installation of a cold weather damper." 


Final thoughts about the Manitou Mastodon Pro EXT 100

"The Mastodon is a polished and composed fork that worked FLAWLESSLY during testing in ALL trail and environmental conditions.   It is the biggest, widest and heaviest fork of the test but the extra heft is not noticeable while riding. 

The wide crown will not be compatible with some frames but I didn’t have any issues with my Fatback Rhino..  For me the limited travel in the PRO EXT 100 as compared to the Wren or the Bluto is the most significant downside of the Mastodon. 

But we are still going to do follow-up testing the Mastodon PRO STD 120 next with 4.8in tires on 82mm rims as we just got word from an Industry Guru, this may indeed work. If so, the downsides for this fork completely disappear."


My Choice

"The Wren was a lot of fun and I wanted to love it, but the inconsistent performance was a deal breaker. 

The PERFECT Fit and Finish, Quality of Construction and Consistent Performance of the Mastodon PRO across a range of temperatures were qualities that I could not live without. 

At the conclusion of this review period I purchased a Mastodon PRO suspension fork from and I look forward to many months of trouble free riding."


Author, Ryan Ellis.







  • OVERALL APPEARANCE                   (30pts)
  • SETUP                                                  (26pts)
  • RIDE QUALITY                                    (108pts)
  • SERVICE / REPAIR                              (26pts)

TOTAL = 230 pts





  • External Fit and Finish :  The sheer design and engineering refinement and clean presentation of the fork.
  • Build Quality :  The level of workmanship, build and quality control exhibited upon inspecting the product against the competition.  Resistance to breaking or needing frequent repairs or warranty work.
  • Packaging / Shipping Protection of the box :  The overall safety and security of the fork in shipment, with respect to its smart packaging techniques to keep it safe from scratching, scuffing, or brake mounts tearing through the box while in transit.



  • Weight :  Most points awarded to the lightest fork weight.
  • Best Travel to AC Height Ratio :  Most points awarded to the forks you can achieve the greatest travel range, while losing the least amount of mm to AC Height requirements.
  • 26" and 27.5" Tire Compatibility :  Most points award to the forks that can accommodate the greatest number of wheel and tire combinations.
  • Axle Design and Quality :  Most advanced, functional, and well thought out axle designs received the highest amount of points.
  • Best 150mm Hub compatibility :  One fork had issues accepting some 150mm standard-sized width TA hubs, due to dropout CNC milling design, and it was scored accordingly, where the other two forks, accepted all standard 150mm hubs we tested.
  • Rigidity / Stanchion Diameter :  Most rigid fork with beefiest Uppers and Stanchions, was scored the highest.



  • Ease of Setup :  How easy is it to calibrate each fork for PSI, Sag settings, and to get it dialed-in for trail riding?
  • Setup and Service Documentation :  How detailed and self-explanatory is the supplied documents that arrives with the fork, or downloadable from the manufacturer's website?  Is it up to date, include the latest tire/wheel combinations, or does it need updating?
  • Minimal Tools Required :  How many tools are required past a shock up (with PSI indicator) and Allen keys, to get the fork dialed in?
  • Air Charts / Sag % Indicators on the fork? :  self-explanatory. (yes/no questions are scored 1=YES, 0=NO)
  • Frame Clearance Issues :  The wider the fork, the least amount of fat bike frames it is compatible with.  Many Fat Bike frames were designed to accommodate the Bluto in 2014, but were not updated since that time, to accommodate the Wren or Mastodon fork widths.  For instance, the Mastodon fork is 23mm or about 1 inch wider than a Bluto. 
  • Accessibility of Dials and Air Valves :  self-explanatory


  • Steering Response :  quick and agile, or sluggish and slow?  Does fork "flex" play into this factor?
  • Full Lockout Switch? :  1=Yes, 0=No
  • Range of Adjustability :  aka = Window of Adjustability for all fork air spring and damper features.  How wide is the range of control?
  • Solo Air Spring w/RCT3 Damper :  rating the Bluto's air spring and rebound damper control system.
  • Twin-Air System w/Damper :  rating the Wren ATK's air spring and rebound damper control system.
  • Durado Air w/MC2 Damper :  rating the Mastodon PRO's air spring and rebound damper control system.
  • Resistance to Fork Flex :  self-explanatory
  • Resistance to Bottoming Out :  self-explanatory
  • Controlled "Top-Out" :  How well does the fork rebound settings, and oil-side damper, control the return stroke from topping out?  
  • Rebound Control :  How advanced is this system?  Are there incremental dial settings, so you can accurately record your configuration?


  • Stock Setup works to (-5c) ? :  Does the stock fork perform to -5c "out of the box", without modification, or degradation in performance?
  • Stock Setup works to (-10c) ? :  Does the stock fork perform to -10c "out of the box", without modification, or degradation in performance?
  • Stock Setup works to (-15c) ? :  Does the stock fork perform to -15c "out of the box", without modification, or degradation in performance?
  • Stock Setup works to (-20c) ? :  Does the stock fork perform to -20c "out of the box", without modification, or degradation in performance?
  • Stock Setup works to (-25c) ? :  Does the stock fork perform to -25c "out of the box", without modification, or degradation in performance?


  • Customer Service Availability :  How easy is it to reach Customer Service via phone or email?  How quick is response time and how helpful are they?
  • Availability and Ship Times of Replacement Parts :  How easy is it to order replacement parts, get warranty service on an item, and get it shipped out for replacement or repair? (this rates response times from Canada).
  • Modular Design / Upgradeability ? :  The fork's design capability of installing enhancements to upgrade from one version to the next, and still use the same chassis.
  • Maintenance Videos :  Manufacturer's commitment to service videos walking the customer through service configuration, repair and modification of the suspension fork.
  • Warranty Support Period :  self-explanatory.  Extended warranty periods scored better.
  • Serviceable at Home w/minimal specialty tools :  All forks required some uncommon tools, but one fork needed only tools acquired from any well-supplied auto-parts store.  The other two forks required special order items.





Thanks again to Ryan Ellis for taking a few months during the Fall of 2017 and early winter 2018 to test all three suspension forks, compile his test results, and write his first online product review! 




This 3-Fork Shootout Review was scored across a total score of 230 points, encompassing 6 main categories, and 36 sub-categories. 

  • We tried to be as fair and thorough as possible
  • We only tested the forks pulled from RANDOM production batch runs that were in stock.   We did not allow manufacturers to hand-pick forks for us to test.
  • All parts were provided by 
  • If a fork failed some part of the test due to mechanical issues, we pulled a second fork, from a different shipment.  If that second fork still failed, we scored that manufacturer based on what was available to us, and docked points for things like Build Quality, and Quality Control consistency. 
  • If a fork did not perform to it's manufacturer-rated cold-weather specification, we scored it accordingly. 
  • We did not install any after-market parts to boost the performance of any "out-of-the-box" stock forks.
  • Our test ran for over 2 months, and included warmer fall weather and terrain, as well as cold winter temps, with snow, ice, and wind chill factored in. 
  • This 3-fork shootout review was conducted by independent testers, with no stakes in any of the companies that manufacture the forks.  
  • Each Independent Tester had owned a Bluto RCT3 for a significant amount of time, before committing to this test. 
  • Non of the Independent Testers had owned a Mastodon fork before this test. 
  • No one was paid for their work. 
  • The Independent Test Scores from all involved were startling similar at the end, with only slight variations.
  • The scores listed here are of the Lead Independent Tester, and the owner of
  • In the way we scored the forks, RIDE QUALITY was weighted so that it comprised of about half the total score awarded.




INNOVATION  -  2014 belonged to the ROCKSHOX BLUTO because this suspension fork ushered in a whole new opportunity for fat bike riders, with its innovative suspension options.  At the time of its release, the Bluto was probably the biggest revolution the sport had seen to date.  This fork opened the door for more advanced frame and component designs, and Industry standardizations.  

LIGHTWEIGHT  -  Weighing in at about 1 lb lighter than the competition, this cross-country inspired design is a good beginner fork to get into the sport, and comes in at a low price point.  Downsides - The lighter weight comes at the expense of durability and fork flex, and this fork is more prone to bottoming-out than the other forks tested.  The Bluto's ride quality was not expected to compete with the Wren ATK or Mastodon PRO on demanding trails, but it was the baseline for our test. 

DURABILITY ISSUES - The most common repair issue is the bushings tend to wear out quickly, and create play in the fork.  All-in-all, the Bluto RCT3 certainly is an improvement upgrade over using a rigid fork, for trail riding enthusiasts.

After owning a Bluto for several solid seasons of riding... riders that upgrade to either a Wren ATK or a Mastodon PRO for more gnarly, aggressive trail riding, should almost instantly see a boost in Ride Quality.




This fork is like a classic muscle car in a way... it can be a lot of fun to own, has its handling limitations when compared to the latest sports cars, might leak oil from time to time, and can require considerable wrenching to pull off that V8 performance. Yet it always has that "wow" factor for its unique look.

The Wren ATK fork did place a respectable second overall, and placed first in the categories of :  

  • Ride Quality
  • Customer Service

That said, this fork has so much potential if quality control levels were maintained consistently.  Unfortunately, we ran into several issues, which ranked the WREN ATK last in several categories including :

  • Build Quality
  • Cold Weather Performance
  • Initial Setup of Twin-Air Spring and Compression /Rebound Damper

When you are dealing with a catalog product, like the WREN ATK series suspension fork, it can be tough to get engineering support, because the OEM manufacturer (MEKKEM SASO Industrial in Taiwan) owns the rights to the fork, and determines things like quality control procedures during production runs.  The state-side manufacturer has very little control of QA (Quality Assurance).  The creator of this suspension fork (the owner of FATLAB) apparently, by summer of 2017, stopped plans to produce the next updated version of this modular-designed fork.  The latest design was version 5, called the "TWIN-AIR".  You can read more about this on the Internet, at many places like THIS LINK , or if your Deutsch is not up to speed, throw it in Google translator and get a rough English equivalent here :  THIS LINK .  (scroll down to the "FATLAB01" entries... starting at 21 FEB 2017, and it goes on for several pages - from their you can pick up the full story of this fork through some Google searches...)

If you own a Wren ATK fork and purchased it prior to the summer of 2017, chances are it works quite well.  If anyone had issues with their fork, we tried our best to swap it out for a replacement, and with a 2 year warranty, everyone is encouraged to contact WrenSports LLC if they have any issues, as Wren does a good job of fielding customer service issues and warranty returns.



  • Ride Quality was excellent, if riding above -5c  
  • Steering was quick and accurate
  • Support videos were excellent
  • Customer Support was always easy to reach and helpful
  • The WREN ATK was compatible with more fat bikes, than the MASTODON PRO, because it had a slightly narrower crown
  • Most tire/rim combinations were compatible with this fork
  • AC Height-to-Travel ratio was good
  • Stiffest fork of the bunch
  • This fork can be set up for very aggressive riding, on fast steep descents.
  • Setup and Service are accomplished with a minimal amount of specialized tools.
  • The Twin-Air Spring is highly adjustable... it just takes time to learn the "dialed-in" settings for different trails (and you need to remember to record those settings, in order to replicate them later on - everything is based off shock pumps - there are no PSI indicators or click/indentable dial gauges with ratios or numbers)
  • 2 year manufacturer's warranty
  • The guys at Wren really do try to connect with their customers and provide personalized service.  That's a benefit of a small company.


  • No matter how well this fork performed, it always seemed to run into problematic issues at some point.
  • the dropouts measured 154mm when the axle was removed.  (they should measure 150).  The extra 4mm caused "bowing" to occur when the fork was clamped down to the hub.  Resulting in 2mm deflection on each fork leg, from crown to dropout.  This caused friction, and resistance... which in-turn affected setting sag up by as much as 40% in one video a customer sent in to us.  This problem also affects overall ease of travel of the fork.
  • Quality Control on the external fit and finish of the fork  (see pictures below)
  • Quality Control on the internals, with respect to cold weather performance failing at or before -8c, instead of -15c.
  • You can control the damper, but it does not offer individual High Speed or Low Speed compression at all.  You can't really get one or the other, all you can do is adjust the damper to dampen the movement of the air spring. (To truly get High and/or Low speed compression, the damper would have to have valves or ports that respond to low speed compressions and then another set of ports or valves that open when the fork is compressed quickly.  This is where the MASTODON PRO damper is years ahead in design and sophistication).
  • There is no PSI gauge, or indicator to let you know the percentage of air in the top vs bottom air chambers.
  • There are no click/indentable/numbered dials for the rebound speed.
  • Changes in temperature (and altitude) affect the Air Pressure and Density of air inside the "Twin Air" system.  (for example, as the temperatures decrease below freezing, the fork acts as if it is "losing" some of the the air PSI - aka - more prone to bottoming out).  This can cause repeated modifications to the PSI settings of the twin air system, to get the same ride quality, at different times of the year.
  • The shipping boxes are less than ideal.  The current packaging configuration encourages scuffs and tiny scratches on the crowns, and the odd brake mount to bust through the box while in shipment. 
  • Poor adhesive bonding and alignment of the Uppers to the Crown occurs sporadically.
  • VERY SHARP machining all around the dropouts is now prevalent and it can easily cut a fingers and knuckles when working the rebound control and/or air cap.
  • by adding the bash guards, you lose 10mm of usable travel.
  • Lack of detailed Twin-Air setup charts for various trail riding configurations (by comparison, FATLAB has detailed setup charts for the same suspension fork design).
  • (pictures of the sporadic manufacturing issues are provided at the end of this review)


The poor cold-weather performance was found on both the 110 and 150 models we had set aside for this review, on bikes in multiple provinces, so the issue was not isolated to one location or source.  Adding the "extreme" cold-weather damper, had no affect.  Forks still froze up between -5c to -8c, as noted earlier in the review.  Neither the factory that makes this fork, nor WrenSports LLC employees could explain why this was happening.

Update:  (9 MAR 2018) The MEKKEM SASO factory initially told us that they were going to manufacture a fork to show us they can pass all the test criteria in this review, including cold weather testing.  We received an email tonight from the Wren OEM factory, that after almost a month of waiting, they are not in a position to send us a fork to test.

Update : (9 MAR 2018)  FATLAB has taken their own suspension fork off their website, and replaced it with the Manitou Mastodon PRO, in all their photos. 

I suspect a lot of Wren owners have been caught by surprise at these results.  I was too.  As I said before, I own a WREN ATK, yet I voted for MASTODON PRO once we really got into the testing.  The winner was emerging early on, and the MASTODON kept in the lead.  MANITOU did their homework.  The MASTODON PRO suspension fork was literally flawless from a consistent, reliable, performance perspective.  

This WREN ATK fork lacks the latest tech advancements and refinements.  It's also the most expensive fork in this competition. 

People are willing to pay for a premium product, but they will demand premium results.  As the most expensive fork in the competition, we expected better build quality, refinement, and consistency.  I've owned several Wren forks and prior to summer 2017, they generally worked better out-of-the-box, than as of late.  

Because of the inconsistencies WrenSports LLC is currently working through, we are offering a sale discount of 30% off on the the remaining forks in inventory.  They carry a 2 year warranty directly through the manufacturer.  You can order via our Contact page.

The decision Ryan and I had to make was a tough one, but we feel it was the correct one, and stayed true to what our goals were when we set out to perform this extended test.




REFINEMENT  -  "2018 belongs to the MASTODON PRO.  With refined execution in build quality, that results in excellent fit and finish, along with consistent problem-free and sure-footed control, this is currently the fat bike fork to buy if you don't want to roll the dice with your money.

CONSISTENT  -  The ride quality of the MASTODON PRO was excellent.  It consistently performed as expected, and worked down to -18c in cold weather riding with zero issues.  The axle design and clamping system is fantastic.  The MASTODON PRO offers both High and Low Speed compression, at the same time, and this is a difference maker for many riders.

On the MASTODON PRO, there were no issues with any 150mm TA hub designs.  The dropouts measured exactly 150mm across when unbolted.  The shipping box protects the fork well while in transit against scuffs and scratches, and arrives at the customer's door with good presentation and a nice collection of setup information guides and charts. 

The main drawbacks on the MASTODON PRO would be :

  • about a 0.25 lb increase in weight over a Wren
  • the widest fat bike suspension fork Crown that fits the least amount of frames
  • a slightly slower steering response
  • a bit of fore/aft flex the heavier riders noticed  
  • Customer Service can sometimes be hard to reach
  • there are 9 versions to pick from (instead of 2)
  • The Travel to AC Height Ratios on the PRO EXT models are the worst of the 3 forks in this test, so on average, you lose 10-20mm of travel to the other competitors, if using 26 x 4.8in or larger tires on your bike.  (See charts at the beginning of the review for a better explanation on why this is the case). 

I think Manitou could revisit their AC HEIGHT / TRAVEL charts and update for riders using 80-83mm rims from many popular wheelbuilding brands, on the most popular tire sizes.  I think this update could save riders 20mm of AC height, and/or gain 20mm of travel, increasing the performance and handling of the fat bike it is installed onto.  Many bikes with PRO EXT forks, just might have done fine with the PRO STD versions instead.

All in all, if this suspension fork can fit on your fat bike, and weight is not a deal-breaker, it is a safe bet, that offers very good performance and excellent build quality.





Quality Control




Quality Control






POOR ADHESIVE JOINT, Left fork upper, where it meets the crown.

VERY SHARP EDGES - Right dropout, REBOUND side.  3mm lip extends off fork dropout and easily cuts anything it comes in contact with.

Chunk of adhesive 7mm wide left on front of fork upper (in plain sight), and then painted over.

POOR ADHESIVE JOINT, Right fork upper, where it meets the crown.

VERY SHARP EDGES - Left dropout, AIR side.  3mm lip extends off fork dropout and easily cuts anything it comes in contact with.

LARGE SCRATCH with pitting in the fork upper, front side, about 25mm wide.  Also painted over at the factory.  (This occurred on 4 forks in a ROW that we unboxed).  This also unfortunately showed up on some customer forks, that we immediately returned and exchanged.  

WREN ATK FORK DROPOUTS MEASURING 154mm (6.05 inches) across, instead of 150mm, in their natural open position.  This caused the stanchions to "bow in" by 2mm on each side and caused enough friction and resistance to affect sag settings by about 40%.  This also affected normal operation of the fork.  Workaround, by adding custom 2mm spacers on each side of the 150mm TA hub, it straighened out the fork legs when the axle was tightened.  Not good.  2 spacers, plus 2-piece axle cap to worry about on every wheel change.  This is happening on the majority of the Wren fork we received.  It's worse on the WREN ATK 150's than on the 110's.



Comparing Control Dials and Axles


Comparing Control Dials and Axles





BLUTO RCT3 - Low Speed compression dial with Lockout switch


MASTODON PRO - HIGH and LOW SPEED Compression dials


BLUTO RCT3 Rebound control dial

WREN ATK Rebound Control - Notice the sharp edge next to the contol knob?  It was sharp enough to cut the skin off your knuckles when adjusting Rebound control.

MASTODON PRO Rebound Control - smooth surfaces, easy to access dial, that had clickable indents to record settings.


BLUTO RCT3 120 Air Filler Cap

WREN ATK 110 - TWIN-AIR FILLER CAP (top chamber)

MASTODON PRO - IVA Incremental Volume Adjust


BLUTO RCT3 MAXLE axle = 50gr on the digital scale

WREN ATK - QR (97gr) and Bolt-on (66gr)  2-piece axles

Mastodon PRO axle = 63gr on the digital scale


BLUTO RCT3 Dropout - measures 149mm with axle removed

WREN ATK Dropouts - measures 153mm wide w/axle removed

MASTODON PRO Dropouts - measures 150mm with axle removed





If you read this far, I will give you some very important information if you are still trying to figure out "Which fork will fit on my bike ??".  The difference is much closer than you may think...

Some handy items to make this measurement easier :

  • a straight-edge 30cm ruler
  • a digital caliper
  • scotch tape
  • black fine point marker
  • right-angled set square

It is very important to get the horizontal measurement precise. 

  1. Remember to apply scotch tape to the frame before using the marker over it. (see pictures for example)
  2. First, use the digital caliper and find the center-point of the headset, when looking at the bike from the drive-side, with the fork turned 90-degrees to the right.  This center-point, is where all other measurements will be based off of.
  3. Line the straight-edge up along the bottom edges of the lower headset bearing cup and draw a thin line on the down-tube, where this line would intersect directly over the fork's outermost edge.  Then measure directly 90 degrees downward to get the second accurate measurement.


WREN ATK :  (1 contact point needs to clear)


  • CONTACT is made 118mm to the left, and 21mm below, the centerline of the (very bottom of the) lower headset bearing cup, when looking at the bike from the drive-side (right side).
  • CLEARANCE (+3mm) would be 121mm to the left, and 24mm below headset centerline, measured horizontally left and below the bottom edge of the headset bearing cups.
  • CLEARANCE (+5mm) would be 123mm to the left, and 26mm below headset centerline, measured horizontally left and below the bottom edge of the headset bearing cups.

NOTE : This measurement is to the lockout level switch, on the right side of the fork crown, which would be the first item on the WREN ATK that would hit a frame, should the clearance not be sufficient, in a 90-degree turn.


MASTODON PRO : (2 contact points need to clear)


  • [Top of HI-LO compression dial] :  CONTACT is made 116mm to the left, and 20mm below, the centerline of the (very bottom of the) lower headset bearing cup, when looking at the bike from the drive-side (right side).
  • [Outer edge of red compression switch] : CONTACT is made 125mm to the left, and 33mm below, the centerline of the (very bottom of the) lower headset bearing cup, when looking at the bike from the drive-side (right side). 

NOTE : BOTH of these items need to clear the frame down-tube, in a 90-degree turn, to the right.

  • [Top of HI-LO compression dial] :  CLEARANCE (+3mm) would be 119mm to the left, and 23mm below headset centerline, measured horizontally left and below the bottom edge of the headset bearing cups. PLUS REQUIRED ADDITIONAL CLEARANCE at (128mm - left) and (36mm - below)
  • [Outer edge of red compression switch] :  CLEARANCE (+5mm) would be 121mm to the left, and 25mm below headset centerline, measured horizontally left and below the bottom edge of the headset bearing cups.  PLUS REQUIRED ADDITIONAL CLEARANCE at (130mm - left) and (38mm - below)


We are in the process of making Autocad templates for this, that can be printed out via PDF, cut out on a piece of paper, and taped to the frame to see of there is collision or clearance.  Once done, we would encourage people to contact us via email for a copy of these guides, and our only "ask" is that you email us back and give your Year, Make, Model, Size of fat bike and let us know of the forks would clear or collide with that frame.  We will build a database from this information and post it online for everyone to use freely.


If you already have one (or both) of these forks on your Fat Bikes, please send us an email with the YEAR, MAKE, MODEL, and SIZE - along with tire brand, size, and rim size, so we can add it to the database of compatible fat bike configurations.  

AS THE DATABASE GROWS, WE WILL POST IT on our site for all to use.  CHEERS!!


Thank You

... time to go Riding !!


Thank You

... time to go Riding !!



brought to you by





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