Wikipedia
Fatbike
A fatbike (also called fat bike or fat-tire bike) is an off-road bicycle with oversized tires, typically or larger and rims or wider, designed for low ground pressure to allow riding on soft unstable terrain, such as snow, sand, bogs and mud. Fatbikes are built around frames with wide forks and stays to accommodate the wide rims required to fit these tires. The wide tires can be used with inflation pressures as low as to allow for a smooth ride over rough obstacles. A rating of is suitable for the majority of riders.