Welcome to the world of Fat Tire Bicycles. Fat Tire Bikes have wide rims, extra-large tires, and oddly-dimensioned frames to make it all fit together to define a fat bike, a cycling subcategory that’s garnered a serious following now.
Improved traction on dirt to flotation when riding through snow, the obese tires let a bike roll where it has not rolled before. With all that squishy rubber under you, suspension is not necessary for most fat bikes.
The wide rubber — some fatty tires are 4+ inches across, or twice as wide as most mountain-bike tire tread — adds notable grip on the ground, and the extra surface area does not allow the wheel to sink as much into soft surfaces like snow or sand.
Another distinction: You can ride with lower tire pressure, (10-15 psi or even lower, depends on your bike model), giving the tire some significant squish translating to more rubber conforming onto the trail for serious grip.