Grinding Brakes: Why It Happens and Why Not to Wait

Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent

Grinding brakes most often mean the brake pads are worn almost or completely through, so metal is rubbing on the brake disc. It is not safe to keep driving on it. Stop driving, get the brakes checked as soon as possible, and avoid hard braking until then.

What causes grinding brakes

Grinding is a harsher, rougher sound than a squeak. These are the common causes:

• Worn-out brake pads. When the friction material is gone, the steel backing plate of the pad presses on the disc, metal on metal. Motability says that if you hear grinding, it is likely the pads have been worn down completely. AAA says grinding means very little pad is left, which can damage other parts.
• Damaged discs. Overheating or long metal-on-metal contact can groove or distort the discs. A cracked disc can also make a grinding noise.
• A sticking caliper. A seized caliper piston or corroded slide pins can keep one pad pressed against the disc, wearing it fast.
• A stone or debris. A small stone or flake of rust can get trapped between the pad and disc and make a scraping sound.
• A bent dust shield. The thin metal shield behind the disc can get knocked and rub on it.
• Missing or worn clips and shims. Without them, the pad can sit at the wrong angle against the disc.
• Heavy rust after standing. A car left parked for a while can build up rust on the discs that grinds as you first move off.

Is light rust ever the cause?

Yes. Light surface rust from damp weather is normally wiped off by the pads after a few stops, and the noise goes.

The difference is that rust noise fades quickly. If the grinding carries on after a few gentle stops, or comes back on every journey, treat it as a fault. Discs that have rusted badly will not clean up by braking and will need replacing.

Why you should not wait

Grinding means parts are rubbing together at high pressure and heat. The longer you drive on it, the more damage it usually does.

• The pads are likely finished. Motability advises that if you hear grinding, you should stop driving and have the brakes checked and replaced as soon as possible.
• The repair can get bigger. Metal pad backing on a disc quickly scores and wears the disc. A job that might have been pads only can turn into pads and discs.
• It is a safety and legal risk. Under the DVSA MOT inspection manual, a pad worn below 1.5mm is a dangerous defect. GOV.UK says you can be fined up to £2,500, banned from driving and get 3 penalty points for driving a vehicle that has failed its MOT with a dangerous problem.

The Highway Code also says not to ignore warning signs, as they could indicate a dangerous fault developing.

Grinding brakes: what to do now

1. Ease off. Leave more space, brake gently and early, and avoid hard stops.
2. Do not drive further than you must. If the grinding is loud, or the car pulls to one side or vibrates when braking, park somewhere safe and get it looked at where it is.
3. Check the dashboard. A brake pad warning light means at least one set of pads is almost worn out. Not every car has a pad sensor, so no light does not mean the pads are fine.
4. Get the brakes inspected. The cause needs to be found, not guessed. Different causes need very different fixes.

If you only hear a squeak, not a grind, read our guide to squeaking brakes. For the early signs to catch before it gets this far, see brake pad warning signs.

What it costs and why

It depends on what we find. A trapped stone can be a quick fix. Worn pads need new pads. If the disc has been damaged by metal-on-metal contact, the discs will usually need replacing too, which is why waiting tends to cost more.

Part prices vary between makes and models. Our labour is £30-£50 per hour depending on the job, plus parts. If you are unsure whether your discs can be reused, our guide on lipped or scored brake discs explains what we look for.

How we can help

Driving a car with grinding brakes to a garage is exactly what you want to avoid. As a mobile mechanic, we come to your home or workplace in Aylesham, Canterbury, Dover, Deal, Sandwich, Folkestone and the villages nearby.

We can inspect the brakes on your drive, find the cause and tell you what it needs. We replace brake pads and brake discs. If the cause is something else, such as a sticking caliper, we will diagnose it and explain the next step. Labour is £30-£50 per hour, parts are extra, and the price is agreed on WhatsApp before work starts. You can also book a consultation.

Frequently asked questions

Can I drive with grinding brakes?
It is not safe to keep driving on them. If you must move the car, drive gently and only as far as a safe place. A mobile mechanic can come to you instead.

Why do my brakes grind only when I first set off?
It may be surface rust after damp weather or the car standing. If it fades after a few gentle stops, that is the likely cause. If it continues, get it checked.

Will grinding brakes fail an MOT?
The noise itself is not a test item, but the cause often is. A pad worn to its wear indicator is a major defect, a pad below 1.5mm is dangerous, and a significantly worn disc is a major defect.

Do I need new discs as well as pads?
Often, if you have driven on grinding pads for a while, because the metal backing scores the disc. It can only be confirmed by inspecting and measuring the discs.

Need help? Send a WhatsApp to 07563 350335 with your car’s make and model and we’ll come to you.

Sources

• Everything you need to know about brake pads (Motability)
• 5 ways to know you may need brake repair (AAA)
• Brakes grinding: symptoms and causes (Mavis)
• Brake noise: grinding and scraping (WhichCar)
• Why do brakes squeal in the morning? (Christian Brothers Automotive)
• MOT inspection manual: brakes (GOV.UK)
• Getting an MOT: after the test (GOV.UK)
• The Highway Code: Annex 6 vehicle maintenance (GOV.UK)