A high-pitched squeal when you brake usually means the pads are getting low, are glazed, or the brakes simply have surface rust after a damp night. A grinding noise is more serious: it usually means the pads have worn through to the metal and are cutting into the rotor, so the car should be checked as soon as possible.
Your brakes are one of the few parts of the car that tell you when something is wrong, as long as you know how to read them. Below is what each kind of noise or feel usually points to, which ones can wait a little, and which ones cannot.
Squealing or squeaking when you brake
A squeal is the most common brake noise, and it has several possible causes.
- Wear indicators. Many brake pads have a small metal tab built in. When the pad wears down close to its limit, the tab touches the rotor and squeals. It is a deliberate warning that the pads are due.
- Surface rust. After rain, a car wash or a damp night, a light film of rust forms on the rotors. The first few stops scrub it off, and the squeak goes with it. This is normal.
- Glazed pads or rotors. Hard braking, riding the brakes downhill or towing can overheat the pads and leave a hard, shiny surface that squeals and grips less well.
- Missing or worn shims and hardware. Pads sit in a bracket with clips and anti-squeal shims. If those are worn, missing or dry, the pad can vibrate and squeal.
- Brake dust or debris. A build-up of dust can cause noise, especially on some pad types.
If the squeal only happens on the first few stops in the morning, it is almost certainly surface rust. If it happens on every stop, all day, it is worth having the pads measured.
Grinding when you brake
Grinding is the noise not to ignore. It usually means one of these:
- Pads worn down to metal. Once the friction material is gone, the steel backing plate grinds directly against the rotor. Braking is reduced and the rotor is being damaged with every stop.
- A stone or debris caught between the rotor and the backing shield. This often sounds like a constant scraping that may come and go.
- Heavy rust on the rotors after a car has been parked for a long time.
A worn pad that is caught at the squealing stage is usually a straightforward pad replacement. Left until it grinds, it often means new rotors as well, which is a bigger job. Our guide to brake pad and rotor replacement explains how that changes what the repair involves.
Judder, pulsing or the car shaking when braking
Sometimes the problem is something you feel rather than hear. A pulsing through the brake pedal, or the steering wheel shaking when you brake, most often points to the rotors.
Rotors can develop uneven thickness from heat, uneven pad deposits or wear, which most people describe as a warped rotor. As the pad passes over the high and low spots, you feel it as a pulse. It is usually most noticeable when braking from higher speed, for example coming off the expressway.
Other causes can feel similar or make it worse:
- Worn suspension bushes or ball joints, which let the wheel move under braking
- A wheel bearing with too much play (see our guide to wheel bearing noise)
- Wheels out of balance, which usually shake at certain speeds whether you brake or not
Because these overlap, a shake under braking needs the car on a hoist so the rotors, suspension and bearings can be checked together. Our suspension and shock repairs page covers the suspension side.
Other brake noises and feelings
- Groaning or creaking at low speed. Often heard when coming to a stop or easing off the brake in traffic. It can be pad material, worn hardware or dry slide pins.
- Clicking when you brake. Usually a pad moving slightly in its bracket, often from worn or missing clips.
- Pulling to one side. Not a noise, but often found alongside one. A seized caliper or sticking slide on one side means that side brakes harder or drags, and the pads on that side wear faster.
- A soft or spongy pedal. This is not a noise problem but it is a safety one. It can mean air in the system, old fluid that has absorbed moisture, or a leak.
When is it urgent?
Some brake noises can wait for your next service. Others mean you should book in now.
Book in soon if you have:
- A squeal on every stop that does not go away after the first few
- Light creaking or groaning at low speed
- Brakes that are noisy after recent brake work
Get it checked as soon as possible if you have:
- A grinding or metal-on-metal noise
- A pulse or shake through the pedal or steering wheel under braking
- The car pulling to one side when you brake
- A soft, spongy or sinking brake pedal
- A brake warning light on the dash
- A burning smell from a wheel after driving
If the pedal sinks towards the floor, or the car does not stop the way it should, do not keep driving it. Have it transported to a workshop rather than driving it in.
If the ABS or traction control light is also on, that points to a different part of the system. Our guide to the ABS warning light explains what it means.
Will noisy brakes fail a WOF?
Brake noise on its own is not listed as a reason for rejection in the NZTA in-service WOF requirements. The faults behind the noise often are. Under those requirements a vehicle can be rejected for brake pads worn below the manufacturer’s specification, discs worn beyond the manufacturer’s specification, leaking calipers or hoses, brakes that pull to one side, or vibration under braking bad enough to affect control. Our guide to what fails a WOF covers the other common fail items.
How we diagnose brake noise
At our Frankton workshop, brake noise is diagnosed on the hoist and confirmed on a road test rather than guessed at. The wheels come off and we:
- Measure pad thickness against the manufacturer’s wear limit
- Check rotor thickness with a micrometer for scoring and minimum spec
- Check the calipers for seized pistons, sticking slides and torn dust boots
- Inspect the brake hoses and lines for perishing, chafing and leaks
- Test the brake fluid for moisture
- Look at the wheel bearings and CV boots while the wheels are off
You get a written report of the pad and rotor measurements, with photos of anything we flagged, and nothing is done without your sign-off.
Get your brakes checked in Hamilton
If your brakes are squealing, grinding or shaking, the sooner they are checked, the more likely it is a simple fix. Our MTA member workshop is at 281 Kahikatea Drive, Frankton, Hamilton, and we give free quotes on brake repairs. Visit our brake repairs page or call us on (07) 847 3339 to book a brake check.