FAT BIKE WHEELSET SELECTION
Tire and Wheelset Combinations
- Top Left : 35mm carbon rims and 2.4in FR and 2.2in RR Continental MTN King and X-King tires (26 lbs)
- Top Right : 35mm carbon rims and 3.0in MAXXIS Chronicles FR and RR (27 lbs)
- Bottom Left : 80mm MuleFUT SL80 rims and MAXXIS Minion 4.8in studded tires FR and RR (29.5 lbs)
- Bottom Right : 80mm MuleFUT SL80 rims and MAXXIS Mammoth 4.0in racing tires FR and RR (28 lbs)
(OD) Outer Diameter Comparisons :
As you can see above, there are 8 comparative cross-section diagrams of the (OD) Outer rim diameter of tires affixed to different rim sizes, that are compatible for FAT BIKE use.
26", 27.5" (also called 650b), 29er, and 27.5+ / 29er+ Boost tire and rim configurations are listed.
This chart will show that some combinations have very similar outer diameters, like the 26x4", 27.5+ x3.0", and 29er x 2.25". All are within 0.6" OD (or 28.7" to 29.3" total OD). Contact patch width will vary between 2.25" to 4.0". XC/AM mid-fat config doing best this summer on bikes with either carbon 27.5 or 29er rims x 3.0in Maxxis Chronicles in tubeless mode, 150m fr TA hubs, Sapim Race spokes, and 197TA rr hubs.
With respect to 26" Fat Bike wheel sets, the debate will continue over 80mm and 100mm rims. Which is better? In addition, are carbon rims best, or are traditional drilled-out lightweight and very strong alloy rims best? The answer all depends on where you are going to doing the majority of your riding.
CARBON RIMS :
If trekking or primarily engaged in x-country riding on rolling terrain, upgrading to carbon rims may be the way to go if you can afford it. The benefits are overall weight savings and less rolling rotational weight translates to less effort to keep the Fat Bike rolling along. This helps in terrain that will always be slowing you down - like beach sand or snow.
ALLOY DRILLED-OUT RIMS :
If riding on very technical courses with lots of rock gardens that have drops and other big "hits" to the rim, probably safer to stay with alloy rims.
100MM RIMS :
100mm rims will widen the sidewalls of the Fat Bike tires by almost an inch. This turns the tire into more of a "low profile" setup...like on a sports car. The tire has less sidewall "flex". Less road/trail shock is absorbed for a given tire pressure. Cornering is noticeably improved with higher tire pressures. Traction is increased in winter.
Benefits : 100mm rims provide better cornering and overall traction.
Negatives : Heavier than 80mm rims, usually more expensive, and somewhat harsher to ride on. Less suspension compliance in the tire itself, because it is being stretched out on a 100mm rim, than on 80mm. Not all Fat Bike frames will accept 100mm rims. Some fat bike tires will blow off 100mm rims, especially during colder winter temps.
80MM RIMS :
Benefits : Widely available. 80mm rims are usually the least expensive of all Fat Bike rim types, and lighter than 100mm rims. They also allow the Fat Bike tire to absorb more road/trail shock and provide more flotation over rocky uneven terrain, which is especially beneficial when used with Rigid forks.
Negatives : Provide less front-line traction at a given tire pressure, because the tire is not as wide, as it would be stretched across a 100mm rim. This can be countered by slightly increasing tire pressure. Cornering is slightly decreased over 100mm rims, and is most noticeable on tight twisting dirt courses. The change in cornering ability is almost unnoticeable when biking in sand and snow.
UPDATE : Since the latest trends has been to go with narrower tires, and narrower rims (for 4 season use). Even though 100mm rims on 5in tires have their place in winter conditions or when maximum traction is needed, they are starting to be phased out. Overall, customers are switching to 80mm rims in winter on 4.5in-4.8in winter tires, and 65-72mm rims with 3.8in-4.25in tires for 3-season (non-snow) riding conditions.
65-72MM RIMS :
Benefits : Lighter than wider rims. Accommodate 3.8in to 4.25in 3-season Fat Bike tires for competition use.
Negatives : Not recommended for use with Fat Bike tires over 4.25in indicated size.
26IN VS. 27.5 FAT BIKE WHEELSETS
2016 announced a few advancements in wheelset attention. One is the thought that 27.5in Fat Bike (wide) rims will provide more traction and weight savings over the same or similar setup in 26in Fat Bike wheelset and tire combinations.
This winter will be the first time the theory can be tested. The calculated difference is a contact patch change of less than 5%. Weight change is minimal. Tire selection for 27.5in Fat Bike rims supporting tires greater than 4.25in is minimal. Trek is pushing this innovation and has produced their own tires under the Bontrager name. Maxxis, who makes Bontrager tires, has also started releasing 27.5+ Fat Bike tires. It should be interesting to see if this trend sticks after the winter of 2017, or if it fades away.
If this trend sticks, expect lots of Fat Bike manufacturers to modify their frame designs to accept 27.5 x 4.5in tires and wheelsets. Many manufacturers have already thought ahead and provided this option in existing designs (such as LaMere and Fatback), but many companies can't support 27.5 x 4.5in tires and wheelsets because the tire/frame combination either rubs, or does not provide enough clearance for snow and mud.
NOTE: We heard a rumor that the 27.5 x 4.5in tires are not clearing the available room on Bluto suspension forks. We are waiting for clarification on this topic. If it's true, this limits the 27.5+ options considerably in winter, for riders using a Bluto RL or RCT3 (and possibly other carbon or suspension forks).
This is a touchy subject among the cycling industry and the hope is that no matter the outcome, it makes the sport better.