Hubs pilot the wheel and brake rotor and are also safety-critical components. In a front-wheel drive vehicle they house the CV joint and transmit power from the drivetrain. In non-drive hubs they facilitate rotation. In all instances, they also hold the wheel onto the vehicle. Hub and bearing design falls into three categories, depending on how the hub/bearing assembly mates with the knuckle/spindle:

• Gen I - bearing presses into the knuckle and the hub presses into the bearing (Illustration)
• Gen II - bearing integral to the hub; hub pressed into bearing and hub/bearing assembly bolts to the knuckle
• Gen III - hub part integral to the bearing, hub/bearing assembly bolted to the knuckle