Brake pads must be replaced immediately when the lining thickness falls below 3 millimetres, a metallic grinding noise occurs when braking, or the braking distance noticeably increases.
In such a situation, a delay of even a few days increases the risk of metal-on-metal contact and a loss of full braking effectiveness. At our workshop, we check the pads and discs first during every service, precisely because the braking system does not tolerate any delay.
In short
- A lining thickness of less than 3 mm is a sign that they need replacing; less than 2 mm is already an emergency situation.
- A metallic grinding noise means the wear indicator is touching the disc – this is not a stage to delay action.
- Vibrations in the pedal and an increased braking distance indicate that the system is not working evenly, not just pad wear.
- At our workshop, we check the condition of the brake pads and discs at every service, regardless of any reported issue.
Contents
2. How many millimetres of lining separate normal wear and tear from a critical condition?
3. What does brake pedal vibration tell us about the condition of the braking system?
4. Why is an extended braking distance a warning sign rather than a minor issue?
5. How do you check the thickness of the brake pads without removing the wheel?
When does a screeching noise from the brake pads indicate an emergency, and when is it simply a sign of wear?
A quiet, metallic squeal that occurs only during heavy braking usually indicates normal pad wear and the activation of the wear indicator – a metal plate deliberately fitted inside the pad, which begins to rub against the disc when the friction material is worn down. A loud, continuous grinding noise audible whenever the pedal is pressed, even lightly, indicates that the metal backing plate of the brake pad is already in contact with the surface of the disc – a situation requiring immediate action, not simply booking the next available appointment. The difference between these two sounds can be difficult for a driver to distinguish, so if you hear any new noise coming from the area around the wheel, it is better to assume the worst-case scenario than to wait for the noise to get louder.
How many millimetres of lining separate normal wear from a critical condition?
Three millimetres of lining thickness is the limit; once this is exceeded, the brake pads lose their full effectiveness and need replacing. Below two millimetres, the risk of the pad’s metal backing plate being exposed and coming into direct contact with the disc increases sharply, and every kilometre driven in this condition accelerates damage to the disc itself. You can assess the thickness of the pad yourself by looking through the holes in most wheel rims, although a precise measurement with a calliper or removing the wheel provides certainty rather than a rough estimate.
What does brake pedal vibration tell you about the condition of the braking system?
Vibration or pulsation of the pedal during braking most often indicates an uneven surface on the brake disc, rather than the pad itself, although both components work in tandem and a neglected pad accelerates disc warping. This symptom usually develops gradually, so drivers get used to the slight vibration over time and stop noticing it, even though it is one of the clearest signs of the system’s deteriorating condition. The longer the vibration is ignored, the greater the likelihood that simply replacing the pads will not be enough and that the discs will also need to be replaced.
Why is an extended braking distance a warning sign rather than a minor issue?
An extended braking distance means that the braking system is applying less friction to the discs than it should, which, in the event of sudden emergency braking, could mean the difference of several metres between coming to a stop and a collision. This phenomenon develops gradually, which is why a driver accustomed to their own car often does not notice the difference until they compare the car’s response with how it behaved a few months earlier. Having to press the pedal too hard to achieve the same braking effect as before is a clear warning sign that cannot be rationalised away by driving style or the time of year.
How can you check the thickness of the brake pads without removing the wheel?
You can assess the thickness of the brake pads without removing the wheel by looking through the ventilation holes in most alloy wheels, ideally in good light or with the aid of a torch. Below, we describe the sequence of steps we follow to carry out a quick assessment of the condition of the pads during a service.
- Park the car on level ground and turn the steering wheel as far as possible in one direction to gain access to the pad through the hole in the wheel rim.
- Shine a torch into the space between the caliper and the disc to get a clear view of the thickness of the friction lining.
- Compare the thickness of the friction lining with the metal backing plate of the brake pad — if the friction layer is already similar in thickness to the backing plate, replacement is urgent.
- Check both sides of the axle, as the pads on one wheel may wear out faster than on the other if there are problems with the caliper.
What happens if we ignore worn brake pads?
Ignoring worn brake pads leads, first and foremost, to damage to the discs, as the pad’s metal backing plate begins to rub directly against their surface, leaving deep scratches. The cost of such a delay is higher than the cost of replacing the brake pads alone, as the bill also includes the replacement of the discs and, sometimes, the repair of a caliper damaged by the uneven operation of the system. That is why, after every pad replacement, we carry out a series of tests in our workshop before the car leaves the bay, to ensure that the system is working as it should, and not just appearing to be in good working order.
When is a check during a tyre change sufficient, and when should you go straight to the garage?
A routine check of the brake pads during a seasonal tyre change is sufficient if the pad thickness is still clearly above the three-millimetre threshold and there are no accompanying noises or vibrations. A metallic grinding noise, a noticeably longer braking distance or the brake system warning light coming on on the dashboard are situations where it is not worth waiting until your next scheduled service. We are open seven days a week, round the clock, including Sundays and public holidays, so in such cases you can bring your car in straight away, rather than driving around for several days with an unreliable braking system.
Summary
- Brake pad thickness below 3 mm is the replacement threshold; below 2 mm is an emergency situation.
- A metallic grinding noise, pedal vibration and increased braking distance are not symptoms to be ignored.
- Delaying the replacement of the brake pads usually results in the discs needing to be replaced as well.
- Our workshop operates round the clock, so urgent brake pad replacements do not require you to wait for an available slot.