Grinding when braking
Where the noise comes from
brakes and steering, the wheel area
Go to the garage without delay
Grinding when braking deserves to be taken more seriously than any squeal. Most often it is pads worn down to the metal: the friction material that rubs against the disc is gone, and the steel backing plate is scraping the disc. The stopping distance grows, the disc is ruined with every stop, and the mechanism can seize.
There are less dramatic versions. A bent disc shield, or a pebble caught between the shield and the disc, makes a very similar grinding noise but does no harm to the brakes. And a short scraping in the first stops after a night outside or after rain is only a film of rust, which the pads clean off in a couple of minutes. The trouble is that these scenarios are easy to confuse by ear, so constant grinding calls for an inspection, not guesswork.
Possible causes
| Cause | How likely | Danger |
|---|---|---|
| Pads worn down to the metal | Most often — if it grinds at every stop | pull over |
| A pebble or a bent shield touching the disc | Common; the sound is similar but harmless to the brakes | shop this week |
| A sticking caliper | If the wheel gets hot and the car pulls to one side | pull over |
| A film of rust after standing or rain | If the sound goes away in the first few stops | safe to drive |
Can you keep driving
With metal grinding on metal, ordinary trips have to stop: all that is acceptable is a careful drive to a garage, keeping your distance and braking early and gently. Putting the replacement off costs money too: every kilometre of grinding adds the price of brake discs to the bill, because the steel backing plate literally machines them away.
If the grinding appeared after standing and went away in the first few stops, drive without limits — that is rust. If the sound is more of a scrape, is heard without pressing the pedal, and the wheel is not hot after a drive, a shield or a pebble is likely: you can get where you are going calmly, but have the car looked at in the next day or two — only an inspection reliably separates the harmless case from worn-out pads.
What to check yourself
- Look for the pattern: a sound only when you press the brake points to the pads; constant scraping while driving points to the shield, a pebble or a sticking caliper.
- Look through the wheel spokes: on many cars the outer pad is visible without dismantling. Friction material thinner than 3–4 mm, or shiny metal instead of it, means replacement immediately.
- After a short drive bring your hand near the wheels without touching the brake disc: if one wheel is noticeably hotter than the rest, that looks like a sticking caliper — the part that presses the pads onto the disc.
- Watch how the car behaves: pulling to one side while braking or a burning smell from a wheel are signs you must not drive with — only carefully to a garage.
- Look at the brake disc through the wheel: deep grooves and a bluish tint to the metal say the grinding has been going on for a while and the discs have already suffered.
Narrow the cause down with questions
Answer a few questions and the diagnostic tree will shorten the list of causes for your case.
How the app helps
The Pro-Stuk app walks you through the same questions — is the grinding constant, does the wheel get hot, does the sound go away after the first stops — and the recording helps tell grinding from the squeal of a wear indicator. The report gives likely causes and a traffic light: safe to drive, show it this week, or drive only as far as the garage.
Common questions
How is grinding different from brake squeal?
A squeal is a high-pitched sound while the brakes still work fully: most often it is the wear indicator warning you in advance. Grinding is a coarse, low metal-on-metal noise: the friction material is gone and the steel backing plate is rubbing the disc. A squeal means booking a garage this week; grinding means stopping ordinary trips.
Is replacing only the pads enough if it was already grinding?
It depends on the state of the discs: even a short time on metal leaves grooves. Shallow ones can sometimes be skimmed, deep ones mean new discs. New pads on a grooved disc brake worse and wear out fast, so the decision is made after an inspection.
The grinding comes and goes — is that dangerous too?
Intermittent grinding is often a pebble between the shield and the disc, and it may fall out by itself. Do not count on it: the same wandering sound appears in the early stage of pads wearing through to the metal. An inspection in the next day or two settles the matter.
The app for iPhone and Android
The questionnaire, the sound recording and the full report with probabilities are all in the Pro-Stuk app.
Installed from a store, the app updates itself.