Brake pads and discs are designed to wear out. The friction material is sacrificial, and replacing it is ordinary maintenance rather than a fault. What matters is noticing where you are in that process, because the last stage — metal against metal — damages expensive parts and lengthens your stopping distance badly.
You do not need tools to spot most of this. You need to pay attention on the drive home.
What you can hear
- A high-pitched squeal when braking, often more obvious at low speed, is frequently the wear indicator doing its job. Many pads carry a small metal tab that contacts the disc once the material is low, deliberately making a noise you cannot ignore. Book the car in.
- A harsh grinding or scraping, metal on metal, means the friction material is gone and the pad backing is cutting into the disc. Stop driving. Every further stop is doing damage and your braking performance is compromised.
- Squeal only on the first stop of the day, especially in damp weather, is usually just surface rust being cleaned off and is not a fault.
Brakes can also squeak for reasons unrelated to wear: dust, cheap pads, or a small stone caught in the works. A noise that appears suddenly and does not clear is worth investigating either way.
What you can feel
- The pedal travelling further than it used to before the brakes bite.
- A pedal that feels spongy, or one that slowly sinks while you hold it at a standstill. Both suggest a hydraulic problem rather than pad wear, and both mean the car should be looked at before it is driven.
- Pulsing or vibration through the pedal under braking, often with a shudder through the steering wheel at higher speed. This usually points to discs that have worn unevenly or distorted.
- The car pulling to one side when braking, which can mean one side is not working properly.
- A longer stopping distance in general, which is easy to normalise gradually and worth being honest with yourself about.
- More handbrake travel than there used to be, or the car creeping on a slope with it applied.
What you can see
On many cars you can see the outer brake pad through the wheel spokes without removing anything. Look at the block of friction material pressed against the shiny disc face.
- New pads start with a substantial block of material. As a general guide, many workshops advise replacement once it is down to roughly 3 mm, but the figure that counts is the one in your service schedule.
- If what you can see looks like a thin sliver against the metal backing plate, have it checked now.
- Look at the disc surface too. A light lip at the outer edge is normal wear; deep scoring, grooves or a heavy blue-ish discolouration is not.
Also worth a glance:
- Uneven wear between the two sides of the same axle, which can indicate a sticking caliper
- A brake fluid level that is slowly falling. This is normal as pads wear, because the pistons sit further out. A sudden drop is not normal — that suggests a leak, and the car should not be driven.
The two dashboard lights, and what they mean
- The red brake warning light can indicate low brake fluid or a fault in the braking system, and on many cars it also simply means the parking brake is applied. If it stays lit with the parking brake released, treat it seriously and stop.
- The ABS light means the anti-lock system has switched itself off. Ordinary braking still works, but you lose anti-lock assistance in an emergency stop. Not a reason to abandon the car, very much a reason to book it in.
Electric and hybrid cars
Cars with regenerative braking often go much further between pad changes, because the motor does a large share of the slowing. That has a side effect worth knowing: pads and discs that are used lightly can corrode rather than wear, and a car that mostly coasts to a halt still needs its brakes inspected on schedule.
How often to check
Look through the wheel whenever you clean the car, and have the brakes inspected at every service. If you drive mostly in heavy traffic, in hills, or with a loaded car, expect to be at the shorter end of any wear interval.
Your manual has the final word
Minimum pad and disc thicknesses, inspection intervals and the meaning of each warning symbol are specific to your car. Where this guide and your owner’s manual or service schedule disagree, follow the manual — and have brake work done by a qualified mechanic.
