The MOT Files

MOT defect file

Brake disc worn, pitted or scored

Last updated

Quick answer

The brake discs have surface wear. Braking is still effective, but the discs and usually the pads should be inspected soon.

Typical cost
£180–£320
DIY viability
Possible with care
Brake disc in cross-section showing wear and minimum thicknessA cross-section through a brake disc. The area swept by the brake pads has worn thinner on both faces, leaving an unworn lip standing proud at the outer edge and near the hub where the pads never reach. Dashed lines mark the manufacturer's minimum thickness, which is stamped on the disc. The worn faces now sit inside those lines, meaning the disc is below its minimum permitted thickness and must be replaced. Wear is exaggerated in the drawing so that it is visible.Original thicknessWorn thicknessUnworn wear lipSwept friction faceBelow minimumMinimum thicknessSection through the disc, with the hub to the bottom
A disc fails the MOT if it is significantly and obviously worn, or worn below the minimum thickness stamped on it by the manufacturer. The raised lip at the edge is the original thickness, which is why running a fingernail across it tells you how much has gone. Wear exaggerated for clarity.

What you might notice

  • A pulsing or juddering felt through the brake pedal under steady braking
  • A scraping or grinding noise that changes as you brake
  • A visible lip around the outer edge of the disc when you look through the wheel
  • Often nothing at all — surface wear is usually found on inspection rather than felt

What causes it

  • Normal wear: discs are a consumable and typically last two to three sets of pads
  • Corrosion pitting on a car that is used infrequently or stood for long periods
  • Worn pads left too long, so the backing plate scores the disc face
  • A sticking calliper slide pin holding the pad in contact with the disc

Advisory or failure?

A disc that is worn, pitted or scored but not seriously weakened is recorded as an advisory. It becomes a major defect once the disc is significantly reduced in thickness, badly scored, or cracked. A disc that is loose, insecure or in danger of failure is a dangerous defect and the vehicle must not be driven.

Can you fix it yourself?

Possible with care

Discs and pads are one of the more approachable jobs for a competent home mechanic, but this is the braking system: it needs axle stands rather than a jack, a torque wrench for the carrier bolts, and a wind-back tool for the rear pistons on many cars. Electronic parking brakes must be put into service mode with a diagnostic tool first, and getting that wrong can damage the actuator.

What it costs

Discs and pads for one axle are typically £70 to £140 in parts for a common hatchback, with the rest labour at around one to two hours. Premium and performance models, and anything with an electronic parking brake at the rear, sit at the top of the range.

What happens if you ignore it

Worn discs do not usually fail suddenly, but they lengthen stopping distances and get more expensive as they go. Running them past the wear limit risks cracking, and a disc that breaks up under heavy braking can destroy the calliper and, in the worst case, jam the wheel.

Common questions

Do worn brake discs fail an MOT?
Not always. A disc that is worn, pitted or scored but not seriously weakened is recorded as an advisory, so the car still passes with it noted. It becomes a major defect, and a failure, once the disc is significantly reduced in thickness, badly scored or cracked. A disc that is loose, insecure or in danger of failure is graded dangerous.
How do I know if my brake discs need replacing?
The clearest sign is a pronounced lip around the outer edge of the disc, which you can usually see and feel through the wheel spokes. A pulsing through the pedal under steady braking points to an uneven disc face, and any scraping or grinding means metal is contacting metal. A good deal of disc wear is only ever found on inspection.
Should I replace brake discs and pads at the same time?
Usually yes, on that axle. Discs typically last two to three sets of pads, so fitting new pads to a disc that is near its wear limit or badly scored wastes both. Doing them together also means one labour charge rather than two, which is why most garages quote for pads and discs as a single job.
How much does it cost to replace brake discs?
Discs and pads for one axle are typically £70 to £140 in parts on a common hatchback, with one to two hours of labour on top. Premium and performance models sit at the top of that range, as does anything with an electronic parking brake at the rear, because the calliper has to be retracted with a diagnostic tool.
Is it safe to drive with worn brake discs?
Worn discs rarely fail suddenly, but they lengthen stopping distances and only get more expensive the longer they are left. Running a disc past its wear limit risks it cracking, and a disc that breaks up under heavy braking can destroy the calliper and, at worst, jam the wheel. Treat an advisory as a prompt to book the work.

Cars this happens to most

Of every model with at least 2,000 tests in the DVSA data, these record brake disc worn, pitted or scored on the largest share of their MOTs. Across all of them the typical rate is 1.0% of tests.

  1. Citroen DS34.9%

    3,330 times in 68,173 tests

  2. Renault Megane4.6%

    4,185 times in 91,287 tests

  3. Skoda Roomster3.6%

    622 times in 17,431 tests

  4. Hyundai IX353.5%

    1,735 times in 49,770 tests

  5. DS DS33.5%

    1,155 times in 33,267 tests

  6. Lexus IS2203.5%

    125 times in 3,602 tests

  7. Renault Scenic3.4%

    1,183 times in 34,458 tests

  8. Citroen C3 Picasso3.2%

    208 times in 6,486 tests

A high rate here is a property of the fleet as much as the car: these models skew old, and almost everything fails more with age. It is a reason to check the item on a used example, not proof the model is badly built. Models with fewer than 2,000 tests are left out because a rate drawn from a few hundred cars moves too much to rank.

Pass rates for every make and model

This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.

Has this been recorded on your car?

Check the full MOT history for any UK registration.

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