What are hub rings and are they required on my wheels?
To understand centering rings you must first understand what a centre bore is. Centre bore refers to the centre hole in the wheel that centres the wheel on the hub of the car. Most alloy wheels are mass-produced, and have a large center bore to accommodate several different vehicles. If this is the case, a hub ring (also referred to as centering rings) will help ensure you are properly centering your alloy wheel on the hub of the vehicle. Steel wheels are usually built in a variety of sizes and are meant to fit your vehicle exactly, so they do not use hub rings.
Hub rings are hard plastic or metal rings that fit between the wheel's centre hole and the vehicle's hub. They make your centre hole smaller so that it will fit your vehicle's hub tightly, minimizing the risk of an off centre, and thus unbalanced, wheel. Without hub rings, tires may vibrate because the wheel may not be precisely centred on the hub.