Lots of fat bikes going out and lots of confusing wheel standards to go with them, so here’s a quick tutorial to help you get fat.
Why is the frame bent?
Some, but not all snow bikes have either their rear triangle, fork, or both offset to the driveside. It makes for a strange looking bike, but there’s a really good reason for it. On some bikes that do not have the 170mm rear hub standard (more on that later), but instead a standard 135mm mountain hub, you can have problems with the chain catching the rear tire in your lowest gears due to the size of the tire. To get around this, some bikes have their rear triangles offset to the right in order to set the cassette out further from the center line of the frame and thus to move the chainline to the right. This moves the chain out of the range of that huge tire.
The only snow bike with both an offset rear triangle and fork is the Surly Pugsley. While other bikes have held true to only have one front and one rear wheel, the Pugsley needs two rear wheels. By offsetting both ends of the bike, Surly made sure that you can swap the wheels back and forth as needed. This allows you to have a cassette on both wheels with different gear ranges or to run a single speed cog on one in case there was a boulder hidden in the fluffy snow drift you just drug your rear derailleur through. You can also run dedicated front and rear wheels if the extra weight of two rear hubs doesn’t sound good to you.
Snow Bike Frame Offsets:
-Salsa Mukluk: none, front or rear
-Surly Pugsley: 17.5mm to the drive-side, front and rear
-Surly Moonlander: 28mm to the drive-side, rear only
-9:ZERO:7 w/135 spaced rear triangle: 17.5mm to the drive-side
-9:ZERO:7 w/170mm rear triangle: no offset
