How to check brake pads and discs

Safety: only do jobs you are confident with. Never work under a car supported only by a jack, and if a repair affects brakes, steering or suspension and you are unsure, have a garage do it or check your work.

In 2025, 10.0% of car MOT tests failed on brakes. Pads worn below 1.5mm, discs that are badly scored or lipped, and imbalance between left and right are the common reasons. You can check pads and discs yourself without taking anything apart, and catching wear early often means replacing pads alone instead of pads and discs.

Warning signs

• A high-pitched squeal when braking. Many pads have a metal wear indicator that squeals when they are nearly worn out.
• A grinding or scraping noise. The pad material is gone and metal is grinding on the disc. Stop driving and get it fixed now.
• A brake pad warning light on the dashboard, on cars with electronic wear sensors.
• Vibration through the pedal or steering wheel when braking, which usually means warped or unevenly worn discs.
• Pulling to one side: a sticking caliper or uneven wear.
• A soft or spongy pedal: possibly air in the system or a fluid leak. This is a safety issue; get it checked straight away.

Checking pad thickness

1. Park on level ground, handbrake on. Turn the steering fully to one side to get a better view of the front brakes.
2. Look through the gaps in the wheel with a torch. You will see the disc and, gripping it, the caliper.
3. Find the outer pad, where its friction material sits against the disc. New pads have around 10–12mm of material.
4. Under 3mm, plan to replace them soon. Under 1.5mm is an MOT failure. If you can’t see clearly, remove the wheel (see safety notes below) or ask a garage to check; many do it free.

The inner pad often wears faster than the outer one and is harder to see, so a pad that looks fine from outside may not be. Rear brakes on many cars are drums, which can’t be inspected without removing the drum.

Checking the discs

• A raised lip round the outer edge of the disc shows how much it has worn. A pronounced lip you can catch a fingernail on suggests the disc is near its minimum thickness, which is stamped on the disc.
• Deep grooves or scoring mean the disc needs replacing, usually with new pads.
• Heavy rust on the braking surface is common on cars that sit unused. A light orange film after rain is normal and wipes off within a few stops; deep pitting is not.

Checking brake fluid

The brake fluid reservoir is under the bonnet, usually on the driver’s side near the bulkhead, with a yellow or black cap. The level should be between MIN and MAX. Fluid drops slowly as pads wear, so a low level can just mean worn pads, but a sudden drop means a leak. Most manufacturers recommend changing brake fluid every two years because it absorbs water over time.

Replacing pads yourself

Replacing pads is within reach of a careful DIYer with the right tools, but brakes are safety-critical, so only do it if you are confident. In outline:

1. Loosen the wheel nuts, then raise the car with a jack and support it on axle stands. Never work under or beside a car held only by a jack.
2. Remove the wheel, then the caliper slide bolts, and swing or lift the caliper off the pads.
3. Note how everything fits (take a photo), remove the old pads, and push the caliper piston back with a wind-back tool or clamp.
4. Fit the new pads and any clips, refit the caliper and tighten the bolts to the manufacturer’s torque setting.
5. Pump the brake pedal until it is firm before moving the car, then bed the pads in gently with several moderate stops.

Always replace pads in axle sets (both front or both rear). Cars with electronic parking brakes often need a diagnostic tool to retract the rear calipers, so rear pads on those cars are usually a garage job.

Which cars fail on brakes most?

From our analysis of every car MOT in 2025, these popular models failed on brakes most often. If you own or are buying one, it is worth checking this area more carefully. Older cars naturally fail more, so the figures partly reflect each model’s age.

See every model in our MOT data by model.

Brakes that are fine at the MOT can still be near the limit. Check the advisories in your car’s MOT history: “brake pads wearing thin” or “discs worn” at the last test means they will probably need doing before the next one.