Introduction - Summer Review




Introduction - Summer Review






(1 AUG 2018)



A comprehensive project was undertaken to perform an unbiased, independent, full product and performance review, of the 2 major players in the Fat Bike suspension fork market, during non-snow conditions.  Data was collected from one year of riding during the warmer summer months, between 2017-2018.

The SUMMER 2018 review of 120mm and 150mm travel forks, is the companion article to the very thorough 3-month WINTER Fat Bike suspension fork competition, that was performed between DEC 2017 and FEB 2018, and focused on fat bike forks with 100-120mm of suspension travel.

This is a fully independent test and review.  We were not solicited or paid, nor provided free gear to test for this review.  All components were purchased off the shelf by  The results are unbiased and reflect the real-world findings during this test.  There was no "reward" or incentive to pick one fork over the other, other than to know we did the best job possible in providing a fair and balanced review.

Disclaimer : The riders testing the the products in this review are not professional MTB racers.  More like weekend warriors, with a passion for the sport, and cyclists for over 20 years.  We like to hit the trails in southern Ontario and Vermont to ride with friends in the summer, and we race Fat bikes in the winter. sponsors several regional races in the winter, cheering on the participants, and giving away draw prizes ranging from tires, to carbon bars, and even suspension forks.  

Some background  on the suspension forks in this review - we have owned the BLUTO RCT3 120, and rode it for 2 years, on several  different fat bikes.  Then switched to the Wren ATK suspension forks, trail riding and racing on them for over a year, on 6 different hardtail and full-suspension fat bikes.  Now we have just about a year under our belt of testing the Manitou Mastodon PRO (STD and EXT) forks on 7 different fat bikes, both hardtail and full suspension.

This review will take two of those Fat bikes, and compare the WREN ATK and MANITOU MASTODON PRO forks, in both 120mm and 150mm suspension travel modes.

This review is to share our experience with the suspension forks and Fat bikes that were tested.  There are more capable extreme riders out there to take these forks to their ultimate limits.  So, if you are one of those skilled riders and have ridden and tested all these forks, we would gladly accept your feedback via email, and would add your performance and scoring data to this article to enhance the review.  The idea is to share accurate information, and keep it brand neutral.  


LAUF CARBONARA - A spring leaf device with less than 60mm of available travel.  The LAUF suspension design does well on fast-paced gravel/CX bikes, but has very limited use in the Fat Bike market. You can read about it, in our LAUF CARBONARA 9-month review.

BLUTO RCT3 120 - Although this XC-based suspension fork ushered in the era of suspension travel for fat bikes, and led to the push in suspension-corrected frame design (transforming the entire Industry), the BLUTO RCT3 is in retirement mode now, past it's prime, and is affectionately called "the noodle".  It cannot in any way, keep up with either the WREN ATK or the MASTODON PRO in an all-out competition.  As such, it is no longer part of our suspension fork competitions.  Many riders may own this fork, and if you are looking for a parallel upgrade, the Manitou Mastodon COMP (STD or EXT) is a good option for entry-level to mid range bikes purchased in 2018 or later.  The Bluto RCT3 forks weigh about 1.2 lbs less than the WREN and MASTODON forks, (and cost less than half as much), but rest assured, adding that additional weight to your fat bike, will result in a significantly more controlled ride.

MASTODON COMP 120 series - We did not consider this modern entry-level/mid-range fork series, because we only want to compare the best product offerings from WREN and MANITOU.  The Mastodon COMP was designed to directly replace the Bluto series on all entry level suspension fat bikes, especially the 27.5 x 4.0+ wheelsets that were not compatible with Blutos.  Manitou does not make a COMP 150mm travel fork either, so it cannot be considered for this competition.

CANNONDALE LEFTY OLAF - this unique fork weighs an extra pound over the Mastodon PRO and WREN ATK.  It has pretty darn good ride qualities.  Drawback is severe incompatibility with the majority of existing wheelsets (due to the Cannondale hub design and lack of manufacturers making the specialty hubs needed for the secondary custom-build market), so this fork is slowly getting phased out to the marketplace.  Owning the Lefty Olaf fork requires owning multiple wheelsets, especially if you wish to switch to a 150TA standardized-hub carbon race fork for winter riding and shed over 4 lbs off you bike weight!  (the Lefty does well on MTB, but probably won't break into the Fat Bike market with any significant strength).  Lastly, this fork does not come in the suspension travel lengths needed for this review.



WREN ATK 120 and 150

Wren Logo


  • Versions : ATK 120, ATK 150 w/Keyed Stanchions

  • Travel : 120, 150mm

  • Hub Compatibility : 150mm thru-axle standard hub

  • Steerer : Tapered head-tube

  • Tire Compatibility : up to 26 x 4.8" and 27.5 x 4.5"

  • Suspension : Twin-Air System w/Damper

  • Lockout control : Yes. Full lockout


MASTODON PRO 120 and 150

Manitou Mastodon


  • Versions : MASTODON PRO STD 120 and EXT 150

  • Travel : 120, 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 : No. Partial lockout only





  • Factory recommended SAG setting = 20%

    • Resulting Travel = 96mm

    • Resulting AC Height = 516mm


  • Factory recommended SAG setting = 20%

    • Resulting Travel = 120mm

    • Resulting AC Height = 540mm



  • Factory recommended SAG setting = 22%

    • Resulting Travel = 94mm

    • Resulting AC Height = 505mm


  • Factory recommended SAG setting = 22%

    • Resulting Travel = 117mm

    • Resulting AC Height = 548mm



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 the suspension 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 a certified suspension corrected geometry, specifically designed for each fork selected in this test, and that means NO VOIDED WARRANTIES by the frame manufacturers (this wipes out the majority of the fat bikes on the market wanting "120"mm travel).

  • Each bike needed to be configured with excellent componentry, including 12spd gearing, premium dropper posts and saddles, strengthened carbon wheelsets (4 season rated), and the bikes needed to be ready for summer riding conditions (w/ appropriate tires).

  • Both test bikes were configured with very similar premium drivetrain and cockpit componentry, so the main difference in the competition was down to the suspension forks.



FATBACK SKOOKUM - EAGLE 12spd - Total race weight of bike was 28 lbs w/ WREN ATK 120 or MASTODON PRO 120 suspension. Dry build weight without pedals or sealant was 26.2 lbs.

2018 FATBACK SKOOKUM (LG), Front Suspension

  • Carbon frame, all-mountain rated, internal dropper post cable routing, suspension corrected to 120mm suspension forks.

  • Chainstay length of 440mm, Headtube angle of 68.5 degrees

  • Designed for aggressive singletrack riding


  • SRAM XO1 EAGLE 12 SPD Drivetrain

  • 9POINT8 FALL-LINE 440x150mm dropper post



  • SHIMANO M8000 Hydraulic Brakes

  • SHIMANO ICETECH 180FR/160RR Rotors

  • DIRT COMPONENTS THUMPER WHEELSET Carbon 83mm width (setup tubeless - Orange Seal) w/ INDUSTRY NINE Torch hubs


  • SQLAB "610" custom fitted saddle (for singletrack riding)

  • Multiple frame-guards protectors built into design




FOES MUTZ150 - EAGLE 12spd - Total race weight of bike was 36 lbs w/ WREN ATK 150 or MASTODON PRO EXT 150 suspension. Dry build weight without pedals or sealant was 34 lbs.

2018 FOES MUTZ 150 (LG), Full-Suspension

  • Hand crafted and welded alloy frame, made in the USA by FOES FABRICATION. Suspension corrected to 150mm travel BOTH front and rear. Internal dropper post cable routing.

  • All-mountain and downhill rated, designed for aggressive trail riding.

  • Chainstay length of 465mm, Head-Tube angle of 65 degrees.


  • SRAM XO1 EAGLE 12 SPD Drivetrain

  • DVO TOPAZ T3 AIR rear shock

  • 9POINT8 FALL-LINE 375x125mm dropper post


  • SRAM GUIDE RSC Hydraulic Brakes

  • SRAM 200FR/180RR Centerline Rotors

  • DIRT COMPONENTS THUMPER WHEELSET Carbon 83mm width (setup tubeless - Orange Seal) w/ INDUSTRY NINE Torch hubs

  • MAXXIS MINIONS FBF4.8 Front and FBF 4.0 Rear EXO-TR-rated Tires

  • SQLAB "610" custom fitted saddle (for singletrack riding)


Quick note on tires.  We need to clearly specify which tires are being used in this competition review for two reasons :

  1. to set the baselines

  2. Confirm that the STD vs EXT versions of the Mastodon PRO suspension fork are fully compatible with these tires. (Some of the Mastodon factory charts need updating - the STD forks fit more tires than the factory charts suggest). Why is this important? The STD version of the fork at any length, has a lower AC Height than the EXT version. As such, the STD version of the fork will lower the front end of the bike 20mm, and accommodate a better ride, assuming the tires/wheelsets used with that fork are fully compatible with it.


We can confirm, and FATBACK BIKES has also confirmed, that the MASTODON PRO STD 120 fork can accommodate the Schwalbe ADDIX Jumbo Jim 26 x 4.8" tires (when mounted on 80-83mm wheelsets) ... even though this tire is not listed as compatible on the Manitou factory charts, for this particular fork.

Note :  The WREN ATK forks fit all 26 x 4.8" tires without needing to refer to any compatibility charts.


All tires were setup tubeless and mounted on the following equipment :

  • Orange Seal Endurance race sealant, tape and Versa valve stems

  • Dirt Components Thumper carbon 83mm wide custom wheelsets

  • Industry Nine Torch hubs (150mm TA FR / 177 or 197mm TA RR)





  • WREN ATK WSF 150-150 (set to 120mm travel)




  • MAXXIS MINION EXO TR 26 x 4.8"


  • WREN ATK WSF 150-150 (set to 150mm travel)


All bikes pictured in this review were custom built by

All photographs, review content, and charts contained in this review are copyright 2018









  • SETUP (45pts)

  • RIDE QUALITY (315pts)

  • SERVICE / REPAIR (65pts)






  • Suspension Fork Price : How affordable is the premium level of this fork model, compared to its available performance?

  • External Fit and Finish : The sheer design and engineering refinement and clean presentation of the fork.

  • Accessory Parts Included : Does the fork packaging include all needed parts to assemble and use the fork out-of-the box? Does the fork include some nice added benefits, such as carbon bash guards, A/C height adjusters, IVA volume adjusters, and Stealth graphics pkg?

  • 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.



  • 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.

  • Fork Seal design and quality : How well does the fork seals keep oil/grease from exiting the fork, and refrain from letting dirt and sand into the fork?

  • 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.

  • Modification needed for all 4 season use : Does this fork require special cold weather seals or dampers? Do these dampers work all 4 seasons, or does this require changing out parts at least 2 times a year? (zero maintenance/modification = highest score)


SETUP    (45 pts)

  • 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 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, includes the latest tire/wheel combination charts?, or does it need updating?

  • Minimal Tools Required for 1st use : How many tools are required past a shock up (with PSI indicator) and Allen keys, to get the fork dialed in? How easy are these tools to obtain?

  • Air Charts / Sag % Indicators on the fork? : self-explanatory. (yes/no questions are scored 5=YES, 0=NO)

  • Accessibility of Dials and Air Valves : self-explanatory.


RIDE QUALITY    (315 pts)

  • Steering Response : quick and agile, or sluggish and slow? Does fork "flex" play into this factor?

  • Full Lockout Switch? : 5=Yes, 0=No

  • High-Speed Compression? : 5=Yes, 0=No

  • Low-Speed Compression? : 5=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?

  • Resistance to Stanchion Shaft Flex : How easy is it to manipulate the fork into allowing stanchion/leg flex during riding? (stiffest fork stanchions scored the highest)

  • Resistance to Axle /Stanchion Flex : How easy is it to manipulate the fork into allowing flex at the junction point of the wheel axle and the lower leg/stanchion? Poor designs score lower. Poor designs allow "wheel deflecting", where the wheel/tire will physically deflect into the left fork leg/stanchion, over some hard hits and terrain features, because of the imbalance in air/oil compression, and rebound control sides.

  • Resistance to Bushing / Stanchion Flex : How easy is it to manipulate the fork under load to flex at the bush fork/stanchion junction? How quickly do the seals deteriorate over time, to create bushing flex?

  • Resistance to Bottoming Out : self-explanatory. Some forks are much easier to bottom out than others...

  • Controlled "Top-Out" : How well does the fork rebound settings, and oil-side damper, control the return stroke from topping out?

  • Overall Ride Quality on a complete race course circuit : This includes varying terrain and speeds, over both XC and downhill trail sections. This is a very important category. Some forks require you to stop and reconfigure for each type of terrain, while some forks can self-adjust on the fly. Other forks never really feel at home, and it's a constant compromise.


SERVICE / REPAIR / VALUE    (65 pts)

  • Customer Service Availability (email and phone) : How easy is it to reach Customer Service? How quick is response time and how helpful are they when they do respond? Do you get the answers to all your technical and service questions?

  • 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 ONLY).

  • Authorized Canadian Service Centres : Are their authorized factory service centres, coast to coast, to address warranty or service issues? 5=Yes, 0=No

  • Maintenance Documentation : How accessible are these documents on the Company websites? How well are those maintenance documents written? How helpful are the diagrams? Do they explain assembly/disassembly/repair well enough to do at home, with the proper tools?

  • Maintenance Videos : Manufacturer's commitment to service videos walking the customer through service configuration, repair and modification of the suspension fork. How easy is it to find these videos on the Company website?

  • Warranty Support Period : self-explanatory. Extended warranty periods scored better. 5pts for each year of warranty coverage.

  • 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.

Many people have asked if we could add comparison data for the BLUTO RCT120 to this 120mm suspension fork test.  So we did!  The results are below :









  3. WREN ATK 150

  4. WREN ATK 120

  5. BLUTO RCT3 120


STD 120

EXT 150


The MASTODON PRO forks are very well made, with high quality machining, and tight tolerances on all the parts.  The external finish resists scratching, and looks great.  All the accessory parts needed to fully adjust and setup your fork are included.  The box is well made to protect the fork while in transit, and the addition of the Stealth decal kit is a nice touch.  This fork comes in at a very good price point for performance-minded riders.

All MASTODON PRO shipping boxes clearly display the actual build date, job queue#, along with the serial# and product description.  This is excellent build quality control measures.  In case an issue is found on a shipped fork, it can be traced back to the crew on duty that created the fork itself, and the supplies and tools used.


In general, the WREN ATK series had the best overall AC/Height ratios.  Whereas the MASTODON PRO STD 120 had the best, and the PRO EXT 150 had the worst.  The WREN ATK and MASTODON PRO both had excellent tire compatibility in 26, 27.5 and 29er sizes.  The Axle design of the MASTODON PRO stole the show.  EXCELLENT AXLE DESIGN, that led to a very rigid dropout, and tightened up the entire fork's rigidity.  The fork seals were of high quality and tight tolerances.  The MASTODON PRO accepted the largest amount of 150mm TA hubs, without any compatibility issues.  There was no modification needed, to make the fork work all 4 seasons between the operating temps of 100F to -10F  (38C to -23C).


This fork was quite easy to set up and fine tune for riding purposes.  It required a few more steps than the BLUTO RCT3, but far less configuring than the WREN ATK. Setup documentation was well provided, with colour information packets included both in the shipping box, and online at the Manitou website support section.  The fork only required a shock pump for setup.  The dials and air valves were well marked and easy to reach and use.



The longer you had a chance to ride the MASTODON PRO, over varying terrain and at different speeds, the more you got to love how well it worked.  It slowly melted away from the conscious, once it was dialed in, and became part of the bike ride itself.  The fork worked as it was designed to, and never let you down.  When adjusting was needed, the dials and air charts were readily available and easy to use.  The IVA internal volume adjustment tokens allowed fine tuning of ramping and lessened topping out. The rebound control had indentable clicks, so you could clearly dial in a setting that was recordable, and repeatable.  High and Low speed compression dials were clearly accessible and marked, with indentable clicks to fine tune and record your settings.

The fork felt well controlled, stable, and took whatever was thrown at it and was ready for more.

This fork did just about everything in excellent fashion.  There were no flaws in the design.  Just two annoyances :

  1. No lockout switch for sprinting or steep climbing

  2. Headset kept loosening up (see explanation below - it's a factory quality control issue that fixes itself over several technical rides - you sort have to "break in" the fork - literally!)


HEADSET ISSUE - well this issue is really a manufacturing problem at the Hayes factory.  When the Manitou Mastodon forks are being made, the steerer tube is pressed into the Crown.  Instead of seating ALL THE WAY INTO THE CROWN, the Steerer has been stopping short by about 3mm.  This means when you cut the steerer, install the fork, and tighten everything up, it all LOOKS OK.  But after you start using the fork on aggressive trails, the steerer will continue to seat further into the crown.  

NOTE : Post-review update 22 AUG 2018 - this phenomena has been occurring with every incoming Mastodon PRO fork.  Each one will need special attention during and after rides, until the steerer tube fully seats in the the crown.  It's a bigger annoyance than previously thought.

Once you start riding, the headset gives you the illusion it is becoming loose.... well what is really happening, is the steerer tube is continuing to "seat" into the crown, and this makes the stem rise, causing the headset spacers to form gaps, and then the headset bearings have no pre-load pressure against them and it all starts to loosen up.  

Here is the solution :

  • pack an extra 3-5mm headset spacer in your bike pack. You are going to need to use it.

  • pack all the allen wrenches needed to tighten the stem bolts and star nut / top cap.

  • ride the bike repeatedly through rocky terrain, or down many flights of cement stairs.

  • the headset will become loose, and start to complain. Stop and tighten it all up.

  • Keep repeating doing this until the top cap is now probably touching the steerer tube. (the 3mm gap that is usually there during installation, will slowly disappear over time, as the steerer continues to seat into the crown). Add the extra spacer you have been tagging along, once the steerer closes that 3mm gap, and touches the top cap.

  • Keep riding. You will know when the steerer is seated by two things happening. 1 - the headset no longer gets loose. 2 - when you run your finger under the crown where the steerer is inserted - it may have started out with a 2mm lip, and then over time, gone flush with the crown, but what you are looking for is when it's about 1mm indented into the Crown. Then it is probably "set" and will no longer need further adjusting.

  • Hayes / Manitou has confirmed this issue and the resolution to it.

>>>  I will add pictures, and links that Manitou sent me pertaining to this issue, as time permits.  <<<

Now back to our RIDEABILITY observations :

Without the lockout switch, you do lose some power transfer on smooth hardpack.

Aside from the above 2 "nuisance" issues, the Mastodon PRO fork has been working in flawless fashion, right through the winter, and into the summer.  Zero return rate, zero warranty calls to date.  This is what a custom builder likes to see in equipment ... it both works well, and doesn't come back with issues and upset customers. 

We have thrown everything at these forks that are mounted to two high-end fat bikes, and the Mastodon PRO has hammered through it all.  This includes a recent trip to Vermont to test the fork on bigger, longer descents, and more technical trails than we have here in southern Ontario.  The Mastodon PRO is so good once setup, that you literally forget that it is there, and can concentrate on your ride and the terrain around you.

As long as front tire pressure is where it should be (usually between 9-15 PSI - depending on tire and rim size), the loads transmitted by the wheelset will travel into the fork, and the front suspension will work it all out, and keep the rear wheel tracking fine.  Having both High and Low speed compression can really come in handy when dealing with fast challenging courses, with long periods that the fork can "pack up" travel... some forks will blow through that travel and start bottoming out, but the Mastodon PRO was not a fork with that issue.  Nor did the Mastodon PRO have issues with excessive topping out.  

The Mastodon PRO is a very well controlled Fat Bike fork and worthy of the win!

Notes on the PRO STD 120 :

The 120mm travel fork is the perfect match for the Fatback Skookum XO1 Eagle that it was tested on.  Fatback ships all Skookums standard, with this exact fork, the Mastodon PRO STD 120.  It accepts the 26 x 4.8in Schwalbe ADDIX Jumbo Jim tires on 26 x 83mm rims with zero issues. 

Notes on the PRO EXT 150 :

Quick item - the MASTODON PRO EXT 150 is an OEM ONLY fork.  You cannot buy in on the open retail market.  As a consumer, you can only acquire it through the purchase of a qualified full suspension frameset, or custom build, such as the FOES MUTZ 150.

The 150mm travel fork had the tallest AC/HEIGHT ratio of all the forks tested.  It was noticeable on climbs, and required a bit more leaning forward to keep the front wheel planted on the steepest climbs.  Once at the top of the trail, and pointed downward, this was a non-issue and the fork performed flawlessly on the FOES MUTZ 150.  A frame hand welded and fabricated just for 150mm travel suspension fat bikes.  (Gorgeous bikes btw!!)

Both the WREN ATK 150 and the MASTODON PRO EXT 150 worked well, when it came to aggressive, bit hit riding and flowing fast descending, but the Mastodon PRO EXT 150 still edged out the WREN on overall ride quality, especially on downhill trails, that switched over to frequent flowy XC sections.  The transition was seemless with the MASTODON PRO, and the fork absorbed it all, and kept the bikes in total control.  The transition was more noticeable with the WREN ATK.

You feel in total control, and throw whatever you can at the MASTODON PRO fork, and it still soaks it up.  I am not a pro rider, nor will you see me in videos jumping airborne across any significant distance, but I do hand the test bikes over to those with the skills, and they provide the hard-core feedback.  They all gave the MASTODON PRO EXT 150 the thumb's up.

Our test bike was a very nice FOES MUTZ 150, all-mountain rated and equipped with SRAM EAGLE XO1 drivetrain with Raceface components rounding out the cockpit and crankset.  The SRAM GUIDE RSC carbon brakes were mated with 200mm FR and 180mm RR Centerline rotors, to provide the best stopping power.  The entire system worked well together, and the DVO TOPAZ T3 AIR mated to the MASTODON PRO EXT 150 into a complete system that just brought smiles to the riders using the bikes and test gear.   

This setup was probably the most fun I have ever had riding downhill on a fat bike, and the best part of it all was we got to do it in a cool place like Vermont!



Customer Service Availability was excellent when trying to reach Manitou by email or phone.  Some days were better than others, but all inquiries were addressed and resolved.  Tech support even provided links to videos and documents, describing some of the engineering choices that were made in the design and fabrication of the MASTODON PRO fork, such as its interesting cable routing.  (When I have more time, i will add those links to this review article).

We sometimes had a two week delay on equipment or parts, but never longer than that, and sometimes, parts/build shipments arrived from the USA in only 3 days.  Same for our suppliers in Canada, if the forks were in stock, they arrived within just a few days time.

Manitou has 2 authorized Canadian Service Centers in Canada, for suspension fork repairs - one in BC and another in Quebec.

Maintenance documentation - Manitou supplied a wealth of setup and service documents for these forks.

Maintenance videos - these were harder to find, but if you were persistent on Youtube, you could find them ... usually authored by several hosts besides Manitou, and MANITOU staff were guests visitors to the bike shop or recording studio authoring the videos.  Manitou could collect these videos and link them back to their support pages to make a more inclusive "library" of their support work.

Warranty - 10 pts for 2 yr warranties and 5pts for 1 yr warranty.

Serviceable at Home with minimal specialty tools - ummm, not really, this is one of those forks you had best send into the professional rebuilders, like S4 Suspension in Quebec, unless, you have all the specialty tools needed, all the spare parts needed, and are really well versed in not damaging the internals when rebuilding a suspension fork.

Another bonus for the MASTODON PRO fork series is that no modification is needed when riding all 4 seasons, with temperatures ranging from 100F down to -10F  (38C down to -23C).  This fork functions in a closed-system to handle those temp extremes without ANY tweaking.


2nd PLACE = WREN ATK 120 and 150



Also known as the "bad-ass looking fork".

We should point out that only 1 WREN ATK fork was needed for this test, as it could be configured as a 120mm travel fork, and as a 150mm travel fork within 15 minutes of service time, due to its modular design.  Once the fork was opened up, tokens needed to be added/subtracted or moved around to modify travel height and AC height.  Fork internals were re-greased, and closed up using readily available tools.  (This is a benefit feature of the Wren ATK forks - easy to adjust AC and travel, and only two forks cover the full suspension travel range from 100-150mm.  Manitou uses 5 forks in the pro model and another 4 forks in the COMP line, to achieve the same feature-set.)

The WREN ATK was the most expensive fork tested.  In addition to the retail box price, you will need to purchase a cold-weather damper for the fork to perform in the same operating ranges as the MASTODON PRO, right out of the box.  This now makes the WREN ATK's total cost about $250 CDN higher than a MASTODON PRO.  This additional cost is really hard to justify, with all things in this review considered.

The external fit and finish on the WREN ATK fork used in this test was acceptable.  Actually better than average of the last few batches we had been shipped that had clear pitting, scratches, or dents on the stanchions.  The forks we tested this time still had the sharp dropouts as mentioned in the winter review, and a few of the same quirks were still evident, but our focus was on how well the WREN ATK could compare to the MASTODON PRO during the summer months, and how much of a gap behind, the BLUTO RCT3 was.

One quick note, there are no manufacturing dates, batch numbers, or any other manufacturing identifiers on the WREN boxes aside from SERIAL# and fork MODEL.  It is anyone's guess, when these forks were actually manufactured.  This is really important as there are regions in time when there were better WREN fork batches than others, as we posted in our winter 2017-18 review.  The MASTODON PRO fork boxes all show manufacturing dates, job queues, serial numbers, and it's clear you can trace those forks back to when they were made, and who was on the production line floor when it was built. 

Build quality award goes to MASTODON.

The packaging of the Wren forks has always been a sore spot for us, as we have received numerous damaged forks... especially if the fork boxes are not double boxed, or they get wet... usually what happened was the brake mounts broke through the shipping boxes and got spurs or were damaged.  The brake mount on this box had broken through, but the bubble wrap had protected the fork.

Shipping Quality award goes to MASTODON



The WREN ATK Series had the best overall AC/Height axle-to-crown ratios.  Except the MASTODON PRO STD 120 beat out the WREN ATK equivalent, and accepted the same wheel sizes.  The MASTODON PRO EXT 150 had the worst AC/Height ratio in the 150mm travel height, and it was noticeable on climbs.  The WREN ATK and MASTODON PRO both had excellent tire compatibility in 26, 27.5 and 29er sizes.

The WREN ATK comes in only 2 sizes, whereas there are 5 different options for the MASTODON PRO.

WREN ATK 110 and 150 vs MASTODON PRO 100 STD, 100 EXT, 120 STD, 120 EXT, 150 EXT.

Less versions usually means you can swap your fork onto another similar fat bike and it will still work.  The WREN ATK 110 covers 80-110mm travel and the ATK 150 covers 120-150mm travel.

Axle Design and Quality - Ohhhh, this is such a sore spot with the WREN ATK forks.  VERY POOR AXLE DESIGN.  The Axle design on the WREN sucks.  Flat out SUCKS.  Even their new design.  SUCKS.  It can cause the front wheel to deflect into the left stanchion, because the Compression and Rebound stanchions have independent (unequal) resistances, and will travel independently... with nothing to lock them into equilibrium - like the LEFTY OLAF for instance, or the superior AXLE designs of the BLUTO or MASTODON forks.  The axle needs to lock the stanchions into a RIGID SYSTEM, but it fails miserably on the WREN ATK.  WREN says to, and I quote, "tighten the shit out of it" ... referring to the axle bolt assembly.  Even if you do, it can still flex and loosen up and the wheel deflects into the left stanchion on fast or hard enough hits.  (It sounds like you bottomed out and tire is rubbing against the crown, except, it's the tire hitting the left stanchion - over time, an arched scratch may form on your left Stanchion, as confirmation of this phenomenon).

Fork Seal Design and Quality - not the greatest.  Right out of the box, about half of the Wren forks are leaking oil or grease.  In the Shootout photos, if you look close, you will see the WREN ATK forks leaking grease/oil... look for the thin "rings" below the bushing collars and forks seals between the lower legs and upper stanchions.  Now, if you do not have the carbon bash guards attached, these leaky seals allow dirt to quickly attach to the lower legs and sooner of later those dust and dirt particles will be driven up into the fork seals and bushings.  In this review, for fun, I included the BLUTO fork scores... and their bushings were even worse... they wore out quickly, and resulted in a clicking noise and some flex when the fork is fully extended... all you had to do was apply the front brakes and gently rock the bike back and forth, and the BLUTO seals/bushings would cause flex.  The WREN design is one step up from that.  The MASTODON PRO design blows them both away.

150mm Hub Compatibility - MASTODON PRO received top marks, along with the BLUTO, as everything we tested them with, worked.  Whereas, the WREN ATK has some issues with several standard 150mm TA front hubs.  The upper milling on the inside of the WREN ATK dropouts would bind with the flanges on some hubs and cause rubbing and/or resistance.  This of course affected performance, and was unacceptable.  Workaround was to add 1.5mm spacers to some hubs, on each side of the dropout, to get the hubs to fit into the fork dropouts, without both sides rubbing.  Problem was, this caused the lower dropout and fork legs to be wider than 150mm internal width.  This "bowed" the fork, and added curvature to the internal shafts, and that added minor deflecting angles to the seals/pistons, and this would cause premature wear and also excessive resistance when setting up SAG.  We took videos of this, but no need to hammer the point home and post them.  The WREN ATK dropouts need a redesign, and we suspect the extra 1.5-2.0mm of shelf milling is an attempt to help secure the axle in place to reduce the chance of the wheel deflection noted above.  Hubs that will fit - Industry Nine Torch.  Hubs that might not fit : many OEM Chinese brands, and some Specialized hubs to name a few.

Modification needed for all 4 season use?  - Yes, installation of cold weather damper (CWD) is now mandatory for below -5C weather.  The swap is fairly quick, if you have the tools.  I mention this because if it is already installed, and the summer month are approaching, you need to swap it back out for the stock oil damper, as the CWD doesn't work as well in hot weather.

All these knocks in the WREN ATK design brought down its scores, and we are completely omitting the issues of the sharp edges on the dropouts near the air and rebound knobs - which we have been told are being addressed with future production releases.  Seriously though, if WREN re-engineered all these issues, and could maintain a higher level of quality control, the fork would be tough to beat.


I will score the WREN ATK 120 and 150 together, because they are basically the same fork, adjusted for different ride heights.  Same internals, same AC Height ratios.  Same exact ride qualities, same adjustment options.  Same PROS, same CONS.

INITIAL SETUP -  of the WREN ATK series forks is always confusing.  It's really easy to grasp the concept of pumping 30 pulls of the air pump into the bottom chamber, and 30 into the top chamber to get started... but from there... it's all a bit of waving the magic wand around and hoping you nail that elusive perfect ratio for the trails you like to ride.  It IS OBTAINABLE, and it does TAKE TIME to do.  Many rides in fact, but if you are patient, and bring your pump with you on multiple rides, and recalibrate the system several times before and during your rides, you will start to see the beauty in the twin-air's ability to arrive at unique dampening ratios.  Just be sure to write down exactly what those ratios were, when you achieved them, and don't let any air out of the system before recording it, or else you just lost that needle in the haystack!

You may be able to find that ratio, and it's like riding in a classic Cadillac with air ride suspension... you just float over the terrain.  It is an amazing feeling, but, it only applies to that specific terrain at that specific speed.  Once you leave that trail section, the fork may become too plush or too firm... for example ... I set up a WREN ATK 110 for a beach run.  This beach section was 3 km long and hard nice hardpack near the water, along with some really loose sections that you need speed to float over... the sand was plush and the tiny pebbles added both traction and about 10-15mm of suspension.  I was able to set up the WREN ATK so it took it all as if it was a flat road, and I hit 47kph doing it.  On sand.  It was phenomenal.  Then I switched over to jumping berms and dunes and the fork went too plush and repeatedly bottomed out.

Roughly speaking, for a 185 lb rider, on XC style trails, look for about 60-70 PSI.  Ratio of 1:3 or 1:4 top:bottom on the pumps.  You rate the fork tuning by the number of pumps you put into the chambers... that is the ONLY accurate measurement you can use.  the PSI pressures may not be all that accurate for the average shock pump, at or around the 50-75PSI levels, as they can run up past 250 PSI, and are more accurate in that region.  Be careful about when detaching the pump, so you do not lose air, as that monkey-roaches up the entire system too.

SETUP DOCUMENTATION - the Wren documentation is not very good, when compared to its competitors.  WREN fails to provide the ever important AIR CHARTS that are BADLY NEEDED to setup this fork.  FATLAB, the European version of this fork, DOES indeed provide Air Charts to their customers.  There are no air charts marked on the WREN fork, nor any air charts marked in any of the documentation.

Minimal Tools required for 1st use - indeed, all you need is an air pump (and a band-aid if you cut your fingers on the sharp edges of the dropouts)

Accessibility of Dials and Air Valves - yes, easy to get to, if you don't cut your fingers or slice off some skin.  (file down or debur the sharp edges on your dropouts after you buy the fork).



First off, the WREN ATK series are better performing forks than any of the BLUTO RL or RCT3 series.  If you own a Bluto, the WREN will beat it flat out.  It's not even close, especially when it comes to ride performance, and you push both forks to the edge of their performance limits.  This assumes SUMMER riding.  We have had intermittent issues with the WINTER performance on the WREN ATK.

There are loyal WREN customers out there, and it is hard to write this article and not upset them (as I own a few WREN ATK forks myself).  The bottom line, is the WREN ATK fork can beat out a Bluto RCT3, but it cannot maintain superiority over a MASTODON PRO when you consider a full race or trail circuit, of widely varying terrain and speeds.  You can dial a WREN ATK in so that it can mimic almost any other fork out there, including even a leaf spring LAUF!  It can impersonate those ride qualities ... stiff and firm, for aggressive hard pack, fire road, paved sections, where all-out sprinting is needed ... this fork excels there, especially with the lockout switch.  Downside is, if the WREN ATK is air chambered for this type of riding, and then you hit slow, rutted, loose terrain... the WREN fork cannot quickly adapt in all situations and still perform at ideal levels.  You may need to stop and recalibrate the air chambers... otherwise is may suddenly feel far too stiff, or, too plush and loose.

The WREN ATK fork has a ton of potential if they went with a 6th version of it (I am told it's currently in the 5th revision, called "Twin Air" - two separate air chambers both top and bottom fed, on the compression side of the fork).  These chambers apparently equalize pressure over time, and have a floating piston between them that is apparently supposed to act like an IVA ramp, as found in the Mastodon PRO.  I found the MASTODON PRO ramps MUCH better, and in logarithmic, rather than linear fashion.  The WREN seemed to ramp in linear fashion... same resistance all the way up to the top-out point (which when you hit it, you think something cracked on the front end of the bike - but Wren LLC states the fork is built strong enough to take the repeated topping out).  The MASTODON PRO ramps up in increasing resistive fashion, so topping out is far less noticeable, if it happens at all.

Heavier riders may prefer the WREN ATK, as it seems to take on 250+ lb riders better than the Mastodon PRO.   I do not have direct experience with this, but it is feedback I have received and seen in the forums.

WREN ATK has a slightly faster steering response, probably due to the rake angle, and the full lockout switch is definitely nice for sprints and steep climbs.

The complete lack of High Speed or Low Speed compression hurts this fork's performance potential.  The designer of the FATLAB/WREN ATK fork was mentioning in a German MTB forum that if a 3rd internal air chamber was added, and a little bit of magic engineering performed, then H/L speed compression might be a real possibility in the modular Wren design.  If so, that could really boost performance of this fork.

The lack of an air pressure dial to show bottom and top air pressure is a bummer indeed, because you can never really accurately determine what the top and bottom air chambers are set to.  Hence, it can be tough to repeat the same exact settings under certain situations.

WREN ATK range of adjustability is the greatest amount of all the forks tested.  Unfortunately, you can never fully know where the floating piston is located in the air side, and under what exact pressures it is facing simultaneously from the top and bottom air chambers.

The resistance to axle and bushing flex (or lack thereof) was covered in earlier sections.  The Keyed stanchions of the WREN ATK Forks are very stiff and strong.  They win top marks for the bunch.

You can configure this fork so that it almost never bottoms-out, whereas, there is less control over the rate at which it tops-out.

Rebound control is fully adjustable.

Overall ride quality on a full race course composed off all major terrains, ascents/descents, and riding speeds, is a solid 8/10.  Bluto scores in at a 6/10 - and it could go lower the more technical and rougher the course.  Mastodon PRO scores in at a 10, if one of them had to score the highest (a 10)....but I still think there is room for a real-world 10/10 Fat bike suspension fork to be created.  No Fat Bike suspension fork to date is perfect, each has trade-offs.



Customer Service Availability - Wren staff are consistent and usually available via email or phone, and readily respond to customer service issues.  This is a strong point of the Brand and the Company.

Availability and Ship Times of Replacement Parts - this can get difficult for Canadian customers.

Authorized Canadian Service Centers - none in Canada.  They all shut down in 2018.

Maintenance Documentation - sketchy, and not well detailed.  Lacks detailed pics.  As compared to the competition, this area needs improvement.

Maintenance Videos - flat out, Russ nailed it with the WREN Service Videos.  Right to the point, well laid out, step-by-step, leaves very little room for error.  Best service videos of the forks tested. 10/10 (get rid of the barking dog, and it's 11/10 !)

Warranty Support - 2yrs full warranty, and WREN does back it up.  Best warranty of the forks tested.  Downside is, most forks NEEDED warranty work within those 2 years.

Serviceable at Home with minimal Specialty tools - Yes indeed.  If you like to tinker, and have a man cave with bike tools, then you will appreciate working on WREN forks.  Only a few tools are needed out of the norm, and they can be acquired by visiting an auto-parts store, and fine tuning them with the use of a grinder.  This makes up for the lack of service centers in Canada.  As long as you can figure out a way to get the parts to you in Canada (from the USA) without paying a lot of duty taxes or shipping, then you are good to go.

One final note : ALWAYS keep the Carbon Bash Guards attached.  If you don't, you are asking for trouble... either the lower legs could become scratched or dented, and that will lead to seal tearing, or oil/grease leaks.  Second, the bash guards shield the lower legs from dust and debris floating up and sticking to the lower leg shafts... and sooner or later, that fine dust or dirt may find its way into the fork.  Be proactive and keep the bash guards attached, and frequently wipe the lower legs clean of debris.

WREN Sports LLC easily wins the SERVICE / REPAIR / VALUE section of the Summer Competition.




The WREN ATK is a solid choice for any BLUTO owner looking to trade up to better suspension (assuming the bike frame is compatible and strong enough for it).  The WREN ATK has a good modular design, and could be a real contender for best overall fat bike fork, if some things about its construction and design were addressed and re-engineered. 

Heavy Riders and Tandem bikes - If rider weight is over 250+ lbs, then the WREN ATK might be the way to go, as the chance for bottoming the fork out is a little less on the WREN, then the Mastodon PRO, when rider weight passes the 240 lb mark.  All bets are off by 300 lbs.

E-Bikes - we do not test them, nor custom build them, and have no plans to do so.  We cannot suggest if the WREN ATK or MASTODON PRO would be better here.  I think both forks would have some structural issues over time, because of the increased torque loads an e-bike can generate at higher speeds, while hitting solid objects on the trail (or on the road - like a curb).  What will break first?  The frame's headtube?  The rim? The fork?  The rider's helmet?  Who knows...  The seals and stanchions on e-bike specific forks need to be reinforced moving forward, because they are under different force loads than previous bike designs.  As Li-Po and other battery technologies emerge to offer more instantaneous power, the forces these e-bikes are subjected to, will continue to rise, and the the weakest links will quickly be found out and will break. (This applies to both the bike and the rider).

At this time, the WREN ATK will easily beat out a BLUTO RL/RCT3, and can nudge out a MASTODON COMP under certain comparisons, but, the MASTODON PRO wins 1st overall, and costs about 20% less than a WREN ATK.

The WREN ATK may have slightly larger, stiffer key-stanchions, but it suffers from the worst axle, bushing, piston and seal designs (all produce flex).  The WREN ATK carbon bash guards look great and do a good job of protecting the lower legs from scratches and debris.  The Achilles' heal of the carbon bash guards is any reverse hit or even a tug from the back, can break them off their mounts.  This can happen from falling forward off the bike and your foot or legs catch the back of the bash guards, or backing up in a wooded area and a bush or twig catches the back of the Bash Guard and breaks it off, or even from some owners pulling their WREN-equipped bikes out of the trunk-space of their car or the inside of their SUV.

The MASTODON PRO does not have a full lockout.  This is a total bummer.  Some people say it's not needed, but I know it really helps with sprinting and climbing, so I say full-lockouts are a definite plus.  Any part of the bike that robs pedaling energy while climbing the access trail to the top of the run, is something you want to minimize.

The MASTODON PRO has that "nuisance issue" of the Steerer tubes not being fully seated into the crown.  This causes the headset to loosen up on the first several rides, until you hit enough rough and tumble terrain, with enough force and energy, to actually seat the Steerer tube fully.  A fully seated Steerer tube, may move up to 3-4mm over the "stock" out-of-the-box position it arrives in from the Factory. (bring a spare 5mm headset spacer with you on the first few rides - so the steerer tube doesn't suddenly come into contact with the top cap, and end your riding day early).  Once this "nuisance issue" resolves itself over time, the MASTODON PRO becomes a solid fork with great reliability and outstanding rideability.

The MASTODON PRO has the superior dropout design, with clean lines, easiest gauge accessibility and highest hub design compatibility.  There are no sharp edges, like found the WREN ATK, when trying to adjust the bottom air or rebound controls.



When you consider all the categories we tested in this SUMMER 2018 FAT BIKE FORK SHOOTOUT, (and in the WINTER 2017/18 FAT BIKE FORK SHOOTOUT) the MASTODON PRO still remains unbeaten, and pulling farther away with the lead.  It is a clear winner as evidenced by the 90% winning score.  (vs. Wren 78%, Bluto 73%)

The BLUTO RL/RCT3 owned the Fat Bike front suspension market when it first came out in about 2014, then the WREN ATK clearly took over for a spell - until about mid 2017.  The BLUTO is now antiquated in both form and function - if you own one, it's definitely time for an upgrade (to a MASTODON COMP, WREN ATK or MASTODON PRO). 

The MASTODON PRO continues to show us that refinement, production consistency, attention to detail, and excellent engineering techniques, have produced the best Fat Bike fork yet to be released on the consumer market in North America in 2018.  

We highly recommend the MASTODON PRO suspension fork on your next Fat Bike.   Cheers !! Logo

Hope you enjoyed reading our review. 

If you are ready for a custom Fat Bike build, please contact us to set up a test ride and build meeting.