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Wheel glossary

A

Alignment

Adjusting the vehicle's wheels, steering, and suspension to the vehicle manufacturer's specifications. When wheels are in alignment, they are in the optimal position, relative to the road and each other. Hitting a pothole or driving over a curb can cause wheels to become misaligned.

Alloy wheels

Wheels made of an alloy of aluminum or magnesium (or both), as opposed to basic steel wheels. In general, alloy wheels are lighter than steel wheels and offer benefits like quicker acceleration and stopping, not to mention enhanced style.

B

Backspacing

The distance from a wheel's mounting surface to its inner flange, measured in inches.

Balancing

Adjusting tires and wheels so that they spin with evenly distributed weight. Tire Technicians place weights on the wheel to make the tire and wheel run true without vibration.

Bolt pattern/bolt circle

The diameter of an imaginary circle that goes through the center of a wheel's bolt or lug holes. Bolt patterns can have 4, 5, 6, or 8 bolt holes. A bolt pattern of 5x120 denotes a wheel with 5 bolt holes and a diameter of 120 millimeters. Also known as bolt circle or pattern circle diameter.

C

Cast wheel

A wheel made by a process in which molten aluminum is placed into a mold of the wheel shape via gravity casting or low-pressure casting.

Centerbore/hub bore

The machined center hole on the back of a wheel, used to center it on a vehicle's hub.

F

Forged wheel

A wheel made from a solid cylinder of alloy material, using a technique that involves extreme heat and pressure.

H

Hub bore/centerbore

The machined center hole on the back of a wheel, used to center it on a vehicle's hub.

Hub centric ring/hub ring

Factory wheels have a center bore designed specifically to fit a specific car. But on aftermarket rims, the center bore is often designed to fit a wide variety of vehicles. In these cases, a hub centric ring is used to match the wheel to the vehicle's hub. This centers the wheel on the hub and prevents vibration.

N

Negative camber

Alignment style where the tops of the tires are angled in towards the center of the vehicle. Generally used on race cars for improved grip while cornering.

Negative offset

When the wheel mounting surface is toward the back, or brake side of the wheel. In a wheel with negative offset, the tire and wheel are moved out of the wheel well, and the wheel has more lip, "dish," on the outside.

O

Offset

Distance from the wheel mounting surface to the centerline of the wheel, in millimeters.

P

Positive camber

Alignment style where the tops of the tires are angled away from the center of the vehicle. Generally used on race cars for improved grip while cornering.

Positive offset

When the wheel mounting surface is in the front half of the wheel, close to the face of the wheel. In a wheel with positive offset, the tire and wheel are tucked into the wheel well with the wheel having little lip or "dish" on the outside.

S

Spin balancing machine

A machine that tells the tire technician how much weight to add to the wheel (and where to add it) in order to properly balance the tire and wheel together.

T

Tape weights

Adhesive weights, available in 0.25-ounce increments, that adhere to the inside barrel of the wheel. Used on custom wheels so weights aren't visible on the outside of the wheel.

Touchless/leverless mounting

A process that uses a machine to install a tire on a wheel without touching the wheel, preventing scratches and other damage. Also makes run-flat tires and low-profile tires easier to install.

W

Wheel diameter

The physical diameter of a wheel in inches, measured from the inside of each flange

Wheel weight/wheel balance

Small metal weights can be attached to the inside or outside of the wheel to help balance the tire and wheel assembly.