Fat Bikes from Surly

Fat bikes, also known as adventure bikes, have huge 4inch tires and are made to ride well in snow, sand, and mud. This bike from Surly is appropriately named "Pugsly."

Dave Gray from surly claims that the massive tires increase traction and float on snow while distributing weight over a larger contact path - kind of like what snowboards do. In addition, the tires provide absorb up to 2.5" on the rigid frame.

Although custom bike builders have been making these types of adventure bikes before, the Pugsley will be the first mass produced one.

Surly Website
Billings Gazette