How fat is fat?


Some people refer to mountain bikes as fat tire bikes. In fact New Belgium Brewery has a nice Amber Ale named Fat Tire with this label:






But some pioneering work, much of it in Alaska, followed by production of bikes and parts by Surly and now HED, have fueled a new bike category, fat bikes.


While mountain bikes often have tires between 2 and 3 inches wide, fat bikes start at 3.5 inches and go to at least 4.8 inches wide. These tires are mounted on extra wide rims and often run in sand and snow with very low tire pressures. Since the big manufacturers have not picked up on this category, the custom builders are cranking them out. In fact there were at least 13 builders showing fat bikes at the NAHBS show in Charlotte.

Here is a nice 1×10 drive train steel frame from 44 Bikes. Fat bikes always have disc brakes, since nobody makes calipers wide enough to accommodate these massive rims. Note the curved seat tube to give more clearance around the rear tire.44bikes Next up is another steel frame from Capitol Bicycles in Ohio. The second picture shows the oval cutouts in the rim. This is to save weight in these monsters and is fairly common.CapitolCapitolRear

Here is another nice fat bike, this time from Ritchey. The close up of the fork shows the tire clearance typically built into these frames.



Another good place for a fat bike is Canada home of Xprezo makers of this bike.

Only slightly south in Michigan, Quiring contributes this red and black tiger stripe fat bike. Again I see a 1×10 drive train. No surprising since there is less to go wrong in the snow and ice.QuiringThe next two fat bikes are both student projects from the University of Iowa. These are built in an interdisciplinary class covering design, materials and engineering. Sure beats the accounting class I had to take back in the day.

While the student bikes are great look at the difference in clean lines when a master builder like Ellis builds a fat bike.


And don’t think that steel is the only material used for fat bikes. This one by Independent Fabrications sports a steel frame, but a closer look at the fork shows some carbon fiber.




But sometimes the whole frame was made of an alternative, like titanium. Like this one by Dean Cycle Works in Boulder.


Or this one by Moots, famous for their titanium work.


We will look at some more ti in a minute, but first lets looks at one more material I saw used in a fat bike, bamboo. Boo Bicycles makes the main tubes from bamboo for this rugged fat bike. With that pack in the middle, this bike is ready for some off-road adventure.


So we have seen a lot of fat tire bikes, but what about suspension? Isn’t that what defines a modern mountain bike? Well of course the fat tires at low pressures (like under 10 lbs) will provide some cushioning. But some builders are coming up with suspension forks to hold the fat tires. Eriksen showed this bike. Again with 1×10 drive train and titanium, but with the addition of front suspension, a Marzocchi Bomber fork. Check out the massive bridge spanning the wide tire and supporting the fork.


Black Sheep, another Colorado builder, went with a lefty fork on this titanium fat bike.


But if you want full-suspension in a fat bike, go for this one from Portland’s Ti Cycles with another lefty fork. But check out the beefy parts in the closeup of the rear linkage and the Fox shock.


The last couple of bikes sport extras to make them suitable for specific purposes. First up is the trail maintenance bike by Moots first shown at last year’s NAHBS. This is a long tail as well as a fat bike. This gives room the chainsaw and the fuel bottle in the cage behind the seat tube.

The other purpose built fat bike is this snow rescue bike from Boo. It is loaded with ropes and other equipment and even skis on special brackets on the rear rack.