Yes, Bigger is Better.
The fat tire revolution started over a decade ago with the introduction of bikes to winter expedition races like the Susitna 100 in Alaska and the need to modify bikes to compete. Check out this 2009 documentary on the origin of Fat Bikes by Carl Battreall.
Riding off road whether on dirt, rocks, sand or snow is better with traction and the larger the volume of tire the lower the air pressure can be used which offers more grip, stability, braking and generally more fun factor. This simple realization has spawned the rapid growth of fat bikes and now is influencing the new developments of mountain bikes in general.
Yes we get asked this a lot so obviously it needs to be included in the FAQ’s and the answer is No. The Fat bike rim and tires were developed along with bike frames to accommodate the size difference. Refer to the video above and it will hopefully make sense why this is not possible.
Now we get to the good stuff and partially what makes Fat Bikes even more awesome is you have many options in one bike to make it suit your riding. Don’t like the MTB wheel size debate? Convert to a Fat Bike and do it all in one! What we mean here is that because of the wide hub spacing and clearance you are free to choose on most frames between a 26”, 27.5” and 29” rim. Most commonly and originally developed was the 26” wheel size which now has the width options from 50mm to as much as 100mm wide. An 80mm width rim being most common. If you plan to run a 3.8-4.25” tire we recommend you keep it light with a narrower rim of 80mm or smaller. If you want the large footprint of 4.8” tires we suggest 80 to 100mm rims which are most ideal for soft snow conditions and lower air pressures. New 29” and 27.5” rims, commonly referred to as 27+ and 29+ are typically 45-55mm wide and are compatible with 2.8” to 3.5” tires. This set up offers a great application for dirt and very hard pack snow condition. Both of these options will offer faster rolling resistance than the traditional Fat tire with a noticeable improvement to braking, comfort and grip of a traditional MTB. These options are most commonly optioned as a second wheel and tire set to adapt your bike from winter to summer yet many riders are happy to run a big rim tire set up all year round.
It seems like every day we are seeing a new tire being offered for Fat bikes and we welcome the wider selection. Good tires can be a big investment but the better quality will offer big returns in comfort, grip and durability. With such a large tire the higher the TPI (threads per inch) the lighter and suppler the casing will be offering both better ride quality and lower rotating weight. Your winter tires are worth an investment as the better rubber compounds do improve grip and will last for many seasons on snow. We recommend 3.25” to 4.25” tires for dirt and 3.8” to 4.8” tires for Snow.
A topic of epic debate is tire pressure. We go by the theory that ideal grip happens when the tire’s height is reduced by 15-20% when weighted. In this case it depends on the weight of the rider, the tires volume and the additional weight packed on the bike. This will typically result in the rear tire being between 5 and 10 psi and the front a 1-3 psi lower (based on 4-5” tires). We suggest increasing your pressure by 2psi for summer or rougher terrain. Only you can choose what’s best for you and we suggest an SKS digital pressure gauge and High Volume Lezyne pump as your best trail companions.
The rear hub on a fat bike must be wider to accommodate the tire sizes. Original fat bike designs like the Surly Pugsley utilize a 135mm rear hub which is offset to the drive side in order to correct the chain line. A 135mm hub is widely available and can offer a front hub swap in certain cases. Most bikes now use a centered 170mm or 190mm hub spacing. Most bikes using 170 spacing will not fit a tire over 4.25” while a 190 spaced frame can use up to 5” tires. 177mm and 197mm spacing refers to rear hubs with thru axles however there are some frames with straight 170 and 190mm and thru axles. Front hubs have been traditionally spaced at 135mm until the release of the Bluto suspension fork which measures 150mm. If you plan on running a suspension fork and you choose a bike with 150mm front spacing as few of the 135mm hubs can be converted to 150mm.
If you ride rough and bumpy terrain or plan to ride year round you will likely at some point want a suspension fork. If you ride only winter we see little advantage on snow trails and a Bluto does not function efficiently in cold temperatures. If you plan on a fork then we suggest you look at bikes compatible with a 100mm Bluto with 150mm fork hub spacing. As for full suspension, we see these as ideal for dirt, rocks and highly technical terrain and if you want to go over anything in your path a full sus. Fat bike will certainly do it. Current models are being built with 170mm spacing for use with 26 x 4” tires or 27+. Personally we feel there is more merit to installing a 27+ wheel set on a full sus. 29er MTB which we have done and quite enjoy!
You will see many fat bikes equipped with simple Avid BB7 or other mechanical brakes. The reason is that some hydraulic brakes are slow to release in cold temperatures. Cable brakes are easy to service and do the job for most winter riding conditions and terrain. With the increase in groomed winter trails, year round use and generally riding our bikes quicker the demand is rising for good hydraulics. We have found the new SRAM Guide to work exceptionally well in all temps. Magura MT8 are also a good choice. Shimano brakes using mineral oil should generally be avoided for winter use below -10c.
This one deserves it’s own section as there are great products and many tips we can offer to keeping comfortable out there. The general rule of layering applies and because cycling is an aerobic sport it is important that your layers breathe (move perspiration out) effectively so you don’t get cold the minute you stop. Visit our full article on dressing to ride.
There are plenty of good winter boots out there to ride in and if you have them it’s a great place to start. When matched with a good spiked/snow shedding pedals (link to shop pedal page) you have a sensible solution. We recommend a 6” winter boot with the use of gaiters for best mobility. If you are used to clipless pedals on other bikes though you will likely desire the added efficiency and control a clip boot like the Lake MX-303(link) or 45Nrth Wolvhammer(Link) provide. Both are quite warm and work great combined with Crank Brothers Mallet(link), Look or Time pedals. Buying a boot slightly larger can allow you better circulation and room for a warmer wool sock or insulated insole.
Pogies are large insulated covers for your handlebars and are a great solution to keep your hands warm for all day touring an less technical terrain. They allow you to wear a lighter glove underneath which will offer better dexterity when it comes to shifting. If you suffer for low circulation or are heading out for a cold all day epic they are ideal. If riding through single track or potential icy trail we prefer to have our hands free.
Our best hand wear solutions are to buy a quality glove or lobster mitt slighting upsized for a non constrictive fit. Add to this a Merino wool liner glove and you have a good combination. Other solutions include having your bike equipped with SRAM’s gripshift and using mitts or for the Ultimate solution we offer the Outdoor Research Lucent or Stormtracker electric heated gloves. Don’t miss our pre-orders on these as they sell out quickly. (link) Another trick is to choose a carbon handlebar matched with ESI silicone grips. This combo reduces potential cooling effect from a typical aluminum handlebar and rubber grips.