FAT BIKE STACK and REACH
Hard Tail (HT) and Full-Suspension (FS)
copyright rideFATbikes.ca 2016-18
This is the Stack and Reach article, including our custom Charts, that was referred to by FAT-BIKE.com, in their FAT CAMP Tech Talk Show (pod cast #19, aired January 7th 2017).
You can listen to that pod cast, while reading this article, by clicking << Here >>. The FAT-BIKE.com review of our website starts at 24min51sec and goes to 32min35sec.
Let me start out by stating I created this web page to share information freely with the Fat Bike community, to help everyone get fitted to the right Fat Bike.
SOME DESIGNS ARE CLEARLY BETTER THAN OTHERS.
" HAVING TESTED OVER 45 fat bike designs by fall 2017, by many different manufacturers and setup with many different suspension configurations, there are very clear choices that offer exceedingly good geometry, handling, and values for the money. "
while others completely missed the mark.
We have taken this information, learned from over three years of INDUSTRY testing and configuring fat bikes (all 4 seasons of the year), and turned OUR BUSINESS into a full custom build service.
Our driving force is still to advocate and help people find the best fitting bikes and gear, so they have the best experience with the sport of Fat Biking, and it becomes a new pass-time for everyone 4 seasons of the year.
The Journey that created these Charts
When I started looking for my first HT (hard tail) Fat Bike several years ago, I was chasing after all sorts of random information online, crunching those numbers, including luring advertisements/marketing and frame colours, seeking the "right fit" and the "right bike". Over the years, I found out that STACK and REACH are by far, the two most important things to consider in finding the right Fat Bike for any given rider. There are many other important secondary factors too, like BB (Bottom Bracket) drop, HT (Head Tube) angle, ST (Seat Tube) angle, and definitely C/S (chainstay) length.
Options like colour, Brand Name on the down-tube, and price, are basically irrelevant, if you can't find a Fat Bike that will properly fit you and accommodate to your riding needs.
You will be throwing your money away on those bikes, and likely to put them up for resale on the secondary market after only owning them for one season or less.
It will amount to you never fully realizing the potential enjoyment and performance in the sport, if you opt to buy the wrong fitting bike, because some advertisement told you to buy brand "xyz", or you liked the colour of a certain Fat Bike, or just because a company makes well-known road bikes, that does not mean they spent the time, effort and engineering on designing a GREAT Fat Bike.
Usually, it's companies that focus all their efforts on, and only manufacture Fat Bikes, that seem to do the best job at bringing true performance and ergonomically correct Fat Bikes to market.
That said, when I realized Stack and Reach were very important factors in finding the right Fat Bike for myself, I started to compile all the frame data over many months, because there was no other source on the Internet with this readily available. What has been compiled here, is to date, probably the most ambitious attempt at cataloging all the Fat Bike frame geometries in production, and available in North America.
If we have missed any frames, please feel free to send us an email, and we can see about adding that brand/model to the list. Our focus is on Fat Bikes in the $2000+ USD marketplace, and under 32 lbs.
Bikes in the $1500 CDN or less market segment might look and sound like real fat bikes, but they tend to fall very short of the mark on many levels, so no sense listing them here. (aka : Moose Bicycles)
STACK and REACH Explained
OK, so what the heck is STACK and REACH..?
With Stack and Reach, you have no need for :
- "SM, MD, LG" or "15, 17, 19, 21" sizing techniques.
- ignore ETT (effective top tube) and HT (Headtube Height).
STACK and REACH will replace all those "traditional" systems of categorizing frames, and it will standardize the cycling industry, not just for Fat Bikes, but for all bikes. (Currently, I think it's most widely depended on, for Time Trial and Triathlon bikes, but it applies to Fat Bikes too!)
Information Required for Proper Frame Fitment
It is best to start out this process by getting the data on two sources of information :
- Knowing the Stack and Reach numbers of your existing Fat Bikes, or best fitting MTBs that you ride.
- Having a Personal Custom Fit Assessment completed.
Most cycling and training centers can perform this fitment test for you. There are even some free "do-it-yourself" Fitment guides online. The idea is to have a really good understanding of your body dimensions. These include (but not limited to) : Inseam, Forearm, Thigh, Lower Leg, Trunk, Sternal Notch, Total Height, and riding style (AM, XC or Adventure/Excursion).
Once you have all these frame and body measurements, they will accurately record your personal data on how your body would best fit on any type of bike.
For each type of bike, Stack and Reach numbers are combined with other critical frame geometry specifications, to arrive at the optimal frame configuration, for your cycling terrain and intended usage.
Why is it helpful to know your existing bike's stack and reach numbers? Because with this information, you can envision how a new bike frame is going to "fit" in relation to what you already have... and you can "fit" this bike into your riding style... be it more downhill, XC, snow-based trekking, or some other race geometry. Some need a longer reach to the bars to be able to move their center of gravity around on the bike... while others may want a taller stack, so the front end is higher up than their previous ride.... or, some racers may want the opposite, to lower the front end and get into more of an aero tuck position for XC racing. Adjusting body position, also adjusts the power transfer from many different leg muscles. Whatever the situation may be... knowing where you are NOW with your current bike's Stack and Reach, is a great starting point, on your journey to where you need to go, to get into an even better Fat Bike geometry.
PRIMARY FOCUS GEOMETRY STATS
For Fat Bike FITMENT, primary importance Frame Geometry numbers are
The next most important frame geometry numbers are
- Chainstay Length
- Stand Over Height (especially for winter riding)
- Bottom Bracket Drop
- Heat Tube Angle
- Amount of Suspension Correction for different forks
- Max Tire Width
Please don't underestimate the importance of these stats, as they can significantly affect (or alter) your riding experience. All Fat Bikes are not created the same. Some are clearly better designs than others.
For Fat Bikes PURCHASED in 2017, the Most Important FRAME Features to Look for are
- Frame Clearance for up to 4.8in tires
- Thru-Axle Hub Spacing of 150mm FR, and 177 or 197 RR
- For All-Mountain riding (AM), frame suspension corrected up to 120mm
- For XC racing, frame suspension corrected to 100mm
- Chainstay length of 435-450mm for AM and XC use, and 455-465mm for general Snow-biking/Adventuring
Frame Geometry Measurements depending on personal taste are
- Seat Tube Angle (angle/position of rider weight over the BB and rear wheel)
- Head Tube Angle (how responsive and "twitchy" will the steering be, vs. how "delayed" it may feel)
- Bottom Bracket Drop (how low, or how tall is the bike's center of gravity)
Trends To Look For in the Fat Bike Industry for 2017
(as compared to previous years 2014-2016)
- MUCH Shorter Chainstays (if your bike is pushing 465+, its outdated and won't handle singletrack as well - aka a "Moose" or "RSD Mayor" bike)
- Stricter warranties on carbon full-suspension Fat bikes. If you want the best survivability on AM trails, go ALLOY FSFB, like the FOES MUTZ. (Several overseas carbon full-suspension frames have been cracking, and/or cannot sustain repeated trail crashes, and must be replaced).
- More Carbon parts (Carbon frame, rims, handlebar, seat post and crankset are now standard on many builds)
- 1x11 and 1x12 SPD drivetrains have replaced 10spd drivetrains. (10 SPD or lower drivetrains are now outdated and being phased out)
- Wheelset accommodations for : 26 x 4.8in / 27.5 x 4.0in / 29 x 3.25in tires.
- Growing interest in strength vs weight savings in carbon wheelsets. example - HED Fat Bike wheelsets are only SNOW RATED, and require a minimum of 8 PSI at all times, to protect from rim strike delamination. Not many are aware of this. Whereas, a seriously engineered carbon wheelset like the Fatback Footprint, is practically AM-rated and can take insane amounts of abuse. The difference in weight can be about 1.25 lbs. But the security factor allows 4-season riding under any reasonable tire PSI.
- Practically all stock rims (alloy or carbon) are now TUBELESS COMPATIBLE. (Very important - read about it << HERE >>)
- Thru-Axle (TA) has replaced Quick-Release (QR). (stay clear of 135mm FR and 170mm RR QR setups as they are now phased out)
- 150mm FR and 197mm RR hub spacing has become the standard for most Fat Bikes. Some PLUS bikes and FSFBs use 177mm TA RR.
- BB drop is averaging 50-60mm.
- 26in rims are now averaging 68-83mm widths. This is down from 80-100mm from previous years.
- 27.5in rims have been introduced, but haven't taken full hold because they can interfere with some suspension fork setups when using 4.5+in tires. (example : 27.5 wheelset, with 4.5in+ tires are not compatible with Bluto suspension forks because of clearance issues). Note the Mastodon PRO EXT and all WREN ATK series of suspension forks are fully compatible with 27.5" fat bike wheelsets.
- Very few bikes now ship with 5in tires on 100mm rims. Trend with "weight weenie" manufacturers is to ship 26 x 4.0in tires on 80mm rims to save weight. (these bikes usually require upgrades to wider tires to handle the snow).
- Alloy Fat Bikes are now 27 lbs or less for the nicer models. 33-36 lbs for the starter models, and above that weight is outdated tech.
- Carbon Fat Bikes are now commonly shipping at between 24-28 lbs, depending on stock configuration. (tires, wheelsets and fork selections make up most of the weight difference between the models, and to a lesser extent, the groupset and crankset purchased affects overall bike weight the most). We recently custom built a 4-season rated 22.1 lb FATBACK CORVUS FLT. Or, snow-rated only, it weighed in at 20.7 lbs.
- Carbon Fat Bike frames are now all generally around 2.75 to 3.5 lbs. Some are only XC rated, while some are further strengthened for AM use (like the Fatback Skookum), and may weigh a bit more...like 1500gr versus 1250gr.
- Medium-Duty Front Suspension : Starter to mid-spec Fat Bikes will ship with either an alloy or carbon rigid fork. Some may ship with the new Mastodon COMP model. (The Bluto is now outdated and not suggested for any build). (The LAUF Carbonara is an event specific fork and not recommended for all-round everyday use).
- Heavy-Duty Front Suspension : Higher-end models are shipping with either a WREN 110 ATK or Manitou Mastodon PRO fully adjustable suspension fork, in replacement of a rigid carbon fork.
- AM hardtail suspension corrected frames are designed to handle 120mm suspension forks. (Wren ATK 110, Wren ATK 120, Mastodon PRO 120 STD / EXT)
- XC hardtail suspension corrected frames are designed to handle up to 100mm suspension forks. (very beginner old-stock 2015-16 models = BLUTO RL or RCT3 100. Advanced 2017 builds include Mastodon PRO 100 STD / EXT and Wren 110 ATK series..that can be configured for 100mm travel and AC "axle to crown" height ).
- AM Full-Suspension frames (like the FOES MUTZ 150), is suspension corrected Front and Rear to 150mm (6in) of travel !! This bike requires a special fork, designed just for it, like the Mastodon PRO 150 EXT and the WREN ATK 150.
- Adventure/snow-bikes do not always have suspension corrected frames, and will ship standard with a nice carbon rigid fork, sometimes with an option for a LAUF Carbonara. (0-15mm of constant operating range (COR) of travel) - NOTE: Lauf Carbonara's do not allow a full 60mm of constant suspension travel, as their name/description may imply). (you can read about that << here >>)
FRAME GEOMETRY LAYOUT
STACK and REACH Definition
"The evolution of mountain bikes has made the old system of top tube and seat tube based sizing irrelevant. The wide range in seat tube angles and bottom bracket heights can create a situation where one bike could feel longer or taller than another frame with the same measurements. Once a rider is in a standing position, the fit and feel of their bike’s cockpit is determined exclusively by the handlebar and pedals. Finding the specific geometric relationship between those two points is the only way to accurately compare the fit and feel of different bicycle frames."
"The horizontal distance from the bottom bracket center to the top of the headtube centerline is referred to as REACH. The vertical distance between these two points is known as STACK. By comparing the reach and stack on different frame models, the rider is able to identify exactly how their bike will fit and feel on the trail. This system eliminates any uncertainty created by the seat tube angle, and forever drops the need for “actual” and “effective” top tube measurements. The reach and stack of a frame is the most important sizing information for a freeride or downhill rider but it is extremely valuable for trail riders, (Fat Bikers) and XC racers as well." (quote taken from Dec 18. 2008 article in Pinkbike).
SEVEN (7) SIGNS YOU MAY BE IN THE WRONG CYCLING POSITION OR ON THE WRONG FRAME :
1. Numb Fingers
2. Lower Back pain
3. Knee pain
4. Saddle soreness
5. Overall lack of comfort, including shoulder or neck pain that accumulates over time
6. Foot or Toe pain on long rides, or while sprinting or climbing
7. Lack of Power Transfer
2017 STACK AND REACH CHARTS
These charts are updated regularly and contain the STACK and REACH data for HARDTAIL and FULL SUSPENSION Fat bike frames available in North America, who publish their frame geometry "Stack and Reach" stats.
If we have missed any vendors in the $2000+ USD marketplace with Fat Bikes under 32 lbs, please let us know, and we will try our best to include those frames in these charts.
FAT BIKE FRAMES - ALLOY
FAT BIKE FRAMES - CARBON
EXAMPLE SIZING CHART
FAT BIKE FULL SUSPENSION FRAMES
This FSFB chart is due for a major revamp as some frames did not pass EFBE or SGS Industry certification testing, and will be removed shortly. Plus at least one overseas manufacturer made engineering mistakes to their front and rear end suspension and tire clearances and basically crippled the release of their FSFB since Interbike).
STACK AND REACH CHART BREAKDOWN
- The STACK of the Fat Bike frames increase as you move vertically from bottom to top of the chart.
- A taller "STACK" basically translates to a more upright riding position (the top of the headset is farther from the ground).
- Riders with longer legs, will definitely want a taller STACK.
- A Fat bike with a tall STACK and short to medium Reach, will put the rider in an upright riding position and more closely resemble all-mountain MTB geometry.
- The "REACH" of the Fat Bike frames increase, as you move horizontally from left to right on the chart.
- As REACH increases, the rider will stretch out more over the frame, in order to reach and hold the handlebars.
- A longer REACH usually is indicative of a longer torso and arms of the rider, and usually translates to taller riders using longer "REACH" on their Fat Bikes.
- A longer reach does not always translate directly into a more comfortable Fat bike... it can easily turn into the opposite. Proper body-fitment sizing is critical.
- XC racers, or winter endurance riders sometimes prefer more "reach"... but it may come at the expense of agility and maneuverability.
- The longer the chainstay, generally the better the steep climbing ability of the frame.
- A longer chainstay can also assist with higher sprint speeds on hardpack, as the rear wheel will track a bit differently, and help keep the bike pointed ahead.
- The shorter the chainstay, the more agile the frame will be in singletrack conditions, and closer resemble MTB geometry.
Note: 7 FAT BIKE frames have adjustable chainstay length settings.
- FATBACK RHINO 440-462mm. Accommodates 27.5+ and 29er+ tire sizes and up to 26 x 4.8in tires on 100mm rims. Sliding rear dropout can also be optimized for Single Speed setups.
- OTSO VOYTEK 430-450mm. Accommodates 27.5+ and 29er+ tires sizes and up to 26 x 4.6in tires on 70mm rims.
- CANYON DUDE 439 to 455mm. Accommodates 27.5 x 3in and 29+ tires. Accepts up to 26 x 4.8in tires on 80mm rims.
- TREK FARLEY 440 to 455mm. Accommodates 27.5 x 3.0in, 29er x 2.4in, and 26 x 4in tires at 440mm chainstay. Accommodates 27.5 x 4in, 29 x3.0in or 26 x 5.0in tires on 455 chainstay setting (according to TREK)
- PIVOT LES FAT 437mm to 447mm. Accommodates 26 x 3.8in, 27.5 x 2.8in, 29 x 2.4in tires at 437mm chainstay. Accommodates 26 x 4.8in and 29er x 3.0in tires at 447mm chainstay (according to PIVOT).
- SALSA MUKLUK 432mm to 449mm. Accommodates 26 x 4.8in, 27.5 x 3.25in and 29 x 3.0in tires.
- VENTANA EL GORDO 438-465mm. Accommodates 26 x 4.8in tires on 100mm rims, 27.5+ and 29+ tires.
Break it down into several key FUNCTIONAL areas
- Frame Stack
- Frame Reach
- Chainstay length
- Personal body fitment measurements
- Rider position vs Rider comfort
- Intended use of the bike (AM, XC, race, adventuring, snow-biking, etc)
- Frame material - Carbon vs Alloy
- Q Factor
- Max tire size
- Singletrack (AM) vs Doubletrack (XC) handling
- 3 season vs 4 season (winter) use
- Rear rack and Pannier bag options
- Frame Front Suspension correction (rigid fork vs suspension fork)
- Frame Rear Suspension travel (for FSFB bikes)
- Thru-Axle Hub spacing
- 1x 12spd vs all other drivetrain options
- GripShift vs Trigger shifting
- Hydraulic vs Mechanical brakes
- Dropper post option
Three Types of Riding Positions
- (AM / Single-track) All-Mountain, Single-track
- most upright. comfortable position
- best frame type for riders with chronic lower back, shoulder or neck pain
- best rider position for climbing, especially steep long climbs
- great at sprinting, if you move forward on the saddle
- AM-suspension frames usually corrected for 120mm of travel (vs 100mm)
- frames accept largest tire combinations
- best frame type for negotiating single-track courses
- frame designs in this category with longer chainstays will generally perform better in the snow
- most upright. comfortable position
- (Adventure / Snow-biking) Double-track, and winter riding
- rider is more stretched out, than AM design
- frames designed for climbing in all conditions, when equipped with longer chainstays
- frames usually designed for sprinting on rolling double-track terrain
- effective design for snow biking and endurance trekking
- frames usually suspension corrected for 60-100mm of travel
- frames usually accept largest tire combinations
- look for frames with lowest stand-over height, when considering a fat bike just for the winter months (*very important*)
- this frame style is not advised for riders with chronic lower back, shoulder or neck pain
- rider is more stretched out, than AM design
- (XC Race) 3-season aggressive XC riding
- very low rider position, rider weight is farthest forward
- frames designed for sprinting and high-speed riding in rolling hard-pack single and double-track race conditions
- tallest riders (over 6ft) may find these frames to accommodate your body geometry best
- while this may not be considered a traditional snow-bike setup, and it can also be set up for Trials/Acrobatic riding
- this frame style is not advised for riders with chronic lower back, shoulder or neck pain
- frame design may not always accept the largest tire combinations (but some companies like Fatback do)
- very low rider position, rider weight is farthest forward
GOAL : You will learn not to make three of the most common buyer mistakes :
- You won't be seduced by "limited time only deals" or closeout bargains online. Why buy a "bargain" bike that doesn't fit you correctly..?
- You won't be seduced by colour schemes, decals, or marketing hype.
- You won't be seduced merely by a brand name. Some of the best Fat Bike manufacturers, are widely unrecognized by the general public, but highly acclaimed within the sport itself. It is worth doing some research to learn more about the different brands available in this sport.
RESULT : You will learn WHICH FRAMES FIT YOU THE BEST, and provide the most current up-to-date build kits. by focusing on those models you can extract maximum power potential and riding enjoyment.
Observing the Results of the FAT BIKE STACK and REACH Charts
These charts were created to fully disclose an unbiased look at all the Fat Bike frames currently offered in North America. We know everyone arrives here already biased from previous marketing ties, or experiences with their previous road or mtb bike Brands. That's fine. We'd ask that you look at this data with an open mind and really consider the possibilities before you make your next purchase in the sport of Fat Biking.
SIGNIFICANT CHANGES FOR 2017 PRODUCT LAUNCHES
The 2017 Model Launch has seen some significant changes happening in the industry. 1) Many companies with unpopular designs from last year dropped out of the market, like Scott. 2) Even more companies got their engineers together and completely redesigned their frames.
Fat Bike companies wanting to stay on the cutting edge of change have re-positioned their "Adventure/Snow" bikes in either the "AM" (All-mountain) or "XC" (cross-country) categories. Trends in these two regions show shorter chainstays overall. Smaller Q factors (Like OTSO). Taller stack and shorter reach for "AM" designs (Fatback Skookum carbon and RM Blizzard alloy), and shorter stack and longer reach for "XC" designs.
One company that always seems to stay ahead of the trending curves and tech changes is Fatback, and they have 3 well-placed models across the geometry sizing spectrum. The Skookum/FLT in "AM", the Corvus/FLT in "Adventure/Snow" and the Rhino/FLT in "XC". All have been fine-tuned with the latest frame geometry updates and can still spec 4.8in tires, using 100mm, or many 27.5+ and 29+ wheelset combinations. They are well placed across the sizing charts and all between 25-30 lbs). This company is passionate about fat bikes and been designing and building JUST fat bikes for about 10 years now.
For instance, the Iditarod Fat Bike Race Across Alaska, has seen Fatback win over a dozen times, in the harshest climates. They even beat the sled dog teams and broke world records !! (click here for more info)
OBSERVATIONS on CHARTED DATA
- Most companies have predictable linear geometry throughout the sizing spectrum... they increase in stack and reach in linear fashion as you progress in size (aka - the bubbles from each size S-M-LG-XL can be connected by an imaginary straight, or slightly rounded line)
- Some companies do not increase their STACK numbers as frame size increases, until they reach the LG/XL models. This is a logarithmic vs. linear STACK/REACH rise.
- For example... a Trek Farley in SM/MD is not going to ride like a Trek Farley in LG/XL. There is a big change in geometry between MD and LG Trek Farley frames. This also applies to the Specialized Fatboy. Don't expect one size of these bikes to ride like another. If you are going to pick your new Fat bikes based on Brand Name, some concessions may need to be made by the rider to properly fit on Fat bikes by companies that increase their frame sizes in this manner. If MD s too small, and LG feels a bit too stretched out, it may be best to look at another Brand all-together. There is no use forcing you to fit on this size, if it doesn't click in just right.
- Some Companies use the SAME STACK on ALL their frames. (RSD Mayor and Framed Alaskan Alloy). The Stack is TALL on all their models, and never changes as frame size increases. Only the REACH increases with frame size. This is hit or miss sizing, and may require longer legs to fit properly on their frames. Both bikes have rather long chainstays (around 470) - so more suited to straight-line snow riding. They will be noticeably harder to navigate and turn in non-snow singletrack conditions, versus a well-handling 4-season fat bike design with chainstays around 455.
- There is a common theme to all the Chinese OEM Carbon FSFB (full-suspension fat bike) frames. They obviously copied the Salsa Bucksaw Carbon frame, and made knock-off designs of their own. Problem is, many of them also are reported to now experience frame cracks on the seat-stays and seat tubes. As tested by the riders at LaMere Cycles. The carbon frame front triangle on the AG-177, CS-01/LLevant Perno (same frame), and iMUST SNO4 Malamute/Growler Double Stout (same frame) appear to be practically identical. The rear frame triangles have been modified by each supplier, in order to adjust the rear hub spacing and bottom bracket size. I am not sure if any of them passed SGS or EFBe Industry Product Testing, as the OEM manufacturers never forwarded passing-grade Industry independent test results to us (we don't accept in-house factory testing, as that is not impartial testing). One set of frame copies went the route of 177 rear axles and 100mm BB spacing, and the other went to 197mm rear axle and 120mm BB spacing (widest in the fat bike market). The linkage systems and rocker arm assemblies on this Chinese OEM FSFB frames have been reported to be weak or wear out quickly.
- One name brand has two different Fat bike models with almost identical frame geometry. This is is the case for the Borealis Echo and Borealis Crestone. (And these seem to be based off the classic "FM190" frame from China, but with an extended ETT). The Echo was released after the FM190. It appears after reviewing the data, that the Echo frame had several modifications made to it during the revision process. Instead of calling it the "Echo v2", these revisions turned into a new frame, and re-marketed under the "Crestone" name. Both frames are within a few millimeters of each other in overall design. Visually, there are several changes to the tube design, and there is a claimed weight reduction. The Crestone is claimed to be a bit lighter and has a lower stand-over height, which are the two main differences over the 2015 Echo version.
- There are about 6 small boutique brands that relabel the FM190 mold geometry as their own brand. They also advanced it into the newer OEM CS197 frame. They all have the same geometry, but some may have different tube shapes. Bottom line, it's the same bike, from the same factory in China. Same durability issues long-term. Several copied the original design process that LaMere used in creating their lightweight carbon hard tail a few years ago. These Chinese OEM agents then copied the LaMere Stack and Reach settings and changed the tube shape and frame name. This results again, in the CS-197/Growler/Llevant hardtail frames. (Catalog frames from China - that stole tech originally from another American company's prototype designs, and then later rebadged with other North American "brand" names) to be sold state-side.
- Only one company had a Fat bike designed with a chainstay that increased in length, as the frame increased in size. That was the Norco Ithaqua carbon. (even though increase was small, 440mm SM, 443mm MD, 445mm LG, 448mm XL. That's an interesting idea.
- Some Fat Bike models border on MTB "PLUS" bike sizing, and rear tire size is limited. As is the case for the Rocky Mountain Suzi - Q, which is limited to 3.8in tires. If you are looking for a narrow "Q" factor, and short chainstay lengths (434mm) like the Suzi-Q, but want more options on rear tire width, look to the OTSO Voytek instead. The OTSO Voytek beats out the Salsa Beargrease and RM Suzi-Q in almost every category for these fat bikes that closely border the "plus" bike region. The Voytek has an adjustable minimum 430mm rear chainstay length, an even narrower Q-factor than a Suzi-Q, and can take up to 4.6in tires on 26 x 70mm rims. The Stack and Reach geometry on both bikes is very similar.