Discs and Rotors

Brake discs, also called rotors, are the metal discs that rotate with the wheel and provide the friction surface the pads clamp onto. They absorb braking heat and shed it into the airflow.

What it does

The disc is bolted to the hub and turns with the wheel. Pads clamp both faces, converting momentum into heat. Ventilated discs use internal vanes to pump air through the disc and improve heat dissipation.

Signs a brake disc is failing

A pulsing or juddering pedal under braking, which indicates thickness variation
A pronounced lip on the outer edge of the disc
Deep scoring or grooves in the friction face
Blue heat discolouration or visible hairline cracking

When to replace them

Often every second pad change, but the decision is made on measurement. Replace once the disc reaches the minimum thickness stamped on its hub face.

What to confirm before ordering

Have these ready and the counter can usually confirm the part in under a minute.

Diameter and thickness, measured on the vehicle
Whether the disc is solid or ventilated
Number of stud holes and the centre bore
Whether an ABS ring or a parking brake drum is integrated

Discs and Rotors by vehicle

Pick your vehicle for the years and engines covered, and what is specific to that application.

Discs and Rotors questions

Can brake discs be skimmed instead of replaced?

Only if skimming leaves the disc above its stamped minimum thickness, and that is often not the case on modern discs which start relatively thin. Measure before deciding, because a disc skimmed below minimum overheats and cracks.

What causes a juddering brake pedal?

Almost always thickness variation across the disc, sometimes from uneven pad material deposits rather than true warping. Either way the disc surface is no longer parallel and the pads grab unevenly through each rotation.

Do discs have to be replaced in pairs?

Yes, across the axle. Different friction surfaces left and right produce uneven braking and pull.