Part explained
Brake discs: wear, thickness and when to replace
Brake discs don't wear with every pad change — they usually outlast two or three pad sets. But once they drop below the minimum thickness or develop ringing or cracking, they become dangerous and must be replaced. This page covers how to measure them, when replacement is due, and what a set costs.
By the onderdelen.autos editorial team · Updated
What do brake discs do?
Brake discs are the cast-iron (or, on some cars, carbon-ceramic) rotors that spin with the wheels. When the brake pads clamp them, motion converts to heat. A hot disc needs to shed that heat quickly — which is why many discs have internal vanes (vented discs).
Symptoms — but always measure
- Vibration or pulsing through pedal or steering under heavy braking (warpage).
- A deep ring or groove on the friction surface — feelable with a fingertip.
- Rust on the outer rim only: harmless, comes off on the first stop.
- Below minimum thickness (stamped on the disc, e.g. 22 mm) — rejected at inspection.
- Cracks or hairlines on the friction surface — replace immediately.
When to replace
Indicative 60,000 – 120,000 km on the front axle. Exact timing comes from measured thickness vs the minimum stamped on the disc. Always replace per axle. On a second pad set with the same discs, measure carefully — discs often survive set 2 but not set 3.
Typical interval: 60,000–120,000 km
What does a set cost?
A set (two discs) per axle runs € 40 – € 220 depending on diameter, material, and brand. Decent used discs from a Dutch scrapyard run € 15 – € 60 — measure thickness and inspect the surface before buying. Workshop labour: often bundled with pads (1 – 1.5 hours per axle).
| Condition | From | To |
|---|---|---|
| New | € 40 | € 220 |
| Used / refurbished | € 15 | € 60 |
Compare new and used discs from Dutch sellers.
DIY?
Difficulty: Medium
Discs and pads together is slightly more work than pads alone: the caliper carrier must come off, and the disc retaining screw can be seized. A seized retaining screw is the classic frustration — use an impact driver or heat gun. If that fails, send it to the workshop.
- Same kit as for pads + a thickness micrometer or calipers
- A ring spanner or socket for the caliper carrier
- Copper grease for the hub face of the new disc
Frequently asked questions
How do I measure disc thickness?
With calipers, at several points across the friction surface (not the outer or inner edge where the pad never contacts). Compare to the minimum thickness stamped on the disc.
Can I buy used brake discs?
Yes — but always measure thickness before paying and check for cracks, deep grooves, or discolouration (overheating). A reputable Dutch dismantler typically supplies a measurement.
Vibration when braking — always the discs?
Usually, but not always. Sometimes it's a sticking caliper piston or unbalanced wheels. Diagnose: vibration in the steering (front axle) or pedal (rear axle)?
How many pad sets per disc set?
Roughly one disc set per two or three pad sets — but always measure, never assume.
Can a new disc be loaded immediately?
Prefer not. The first 200 km of gentle braking builds the friction transfer layer onto the disc.
Related parts
Brake discs from Dutch inventory
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