Brake Discs
A brake disc is a cast-iron rotating disc that turns with the wheel hub and slows the car when the pads are pressed against it.
Prepared by the Bicops Technical Content Team · Last updated:
Shop Brake DiscsWhat does it do?
The disc absorbs the heat generated during braking and releases it into the air. That is why front wheels mostly use vented discs with an air channel between two faces, while a solid disc can be enough at the rear where loads are lower. Drilled and slotted types are designed to clear the gas and dust layer that forms at high temperatures.
How do you know it needs replacing?
Vibration in the steering wheel or pedal while braking is the most common sign that heat has warped the disc. Deep grooves you can feel with a fingernail, a pronounced lip at the edge, blueing or fine cracks also call for replacement. Every disc has a minimum thickness stamped on it; below that value the disc cannot be skimmed and must be renewed.
What to look for when choosing
Disc diameter, thickness, bolt count and hub size must match the car exactly; different engine options of the same model often use different discs. That is why selection should be made by OEM number. Discs are always replaced in pairs per axle, and fitting new pads at the same time lets the two parts bed in together.
Frequently Asked Questions
Can brake discs be skimmed?
Yes if they are above the manufacturer’s minimum thickness, but skimming removes material and shortens their life. As the price gap has narrowed, discs are usually replaced instead.
Is braking vibration always a disc fault?
Usually it comes from disc run-out, but loose wheel bolts, a worn ball joint or unbalanced tyres produce the same symptom. Measure run-out before replacing the disc.
Do drilled discs brake better?
In everyday driving the difference is not noticeable; drilled and slotted discs are designed to improve heat dissipation at high temperatures and only really pay off under sustained hard braking.