 The "road wheels" are a series of non-powered wheels between the drive sprocket and idler wheel that serve to support the weight of the vehicle (and thus aren't considered "idle", even though they are unpowered).In higher speed applications, such as tanks and other AFV's, these road wheels are typically given some sort of suspension system to ease the ride, increase controllability, and decrease wear and tear.Due to the complications in adding suspension systems to the idler wheel and, in particular, the drive sprocket, in such vehicles, the road wheels typically carry all of the weight of the vehicle.