What is a hub bearing on a car? A hub bearing serves two primary purposes. The first is to allow the hub and attached components -- the brake disc and the tire and the wheel -- to rotate freely, and also to keep the said wheel tire and rotating mass attached to the car. There are two primary types of hub bearings. The more common on modern cars is a unit bearing, where the inner and outer bearing, seals and grease are all in a single unit, and it's installed as one piece. And if it fails, for any reason, it's not serviceable, so it has to be replaced altogether. Another style of wheel bearing would be a separate bearing for the inner and outer side of the hub that ride on a spindle, and these bearings are removable and serviceable individually as are the seals, and they do need to be greased on a regular basis to make sure that they spin freely and don't wear. Typically, if a hub bearing fails, you will notice a grinding or a...other noticeable sound going in a certain direction. Usually if you're turning to the right and you hear a grinding noise on the left, that means that your left hub bearing is worn out. And likewise, if you're turning to the left and you hear a noise coming from the right wheel bearing -- a grinding noise or the like -- the most likely symptom or cause is the wheel bearing on the right hand side.
A hub bearing on a car servers two primary purposes, including allowing the hub and attached components to rotate freely, and also to keep the wheel tire and rotating mass attached to the car. Learn about the two types of hub bearings, including unit bearings and wheel bearings, with help from an auto mechanic in this free video on auto parts.