When to replace brake pads and rotors, and what to look for

How pads and rotors wear

When you brake, the calipers squeeze the pads against the rotors, the discs the pads clamp onto, and the friction turns the car's momentum into heat. The pad's friction material is the part meant to wear, so that the rotor underneath is not damaged.

The rotor absorbs and dissipates that heat, and every rotor has a minimum thickness specification. A rotor with minor surface wear or light rust can sometimes be resurfaced, machined to a smooth, flat surface again, but once that would take it below the specification, or it is already close, replacement is the only safe option.

If the pads are left until the friction material is gone, the steel backing plate meets the rotor, and the rotors have to be replaced as well.

Signs they need replacing

• A consistent high-pitched squeal every time you brake, usually the pads' built-in wear indicator
• The brake pad wear light, which means the pads have worn down to the warning limit
• Pads that look thin when you look through the wheel spokes
• Grinding or a metal on metal sound, which usually means the pad material is already gone
• A pulsing or vibrating pedal, which usually points to the rotors rather than the pads
• Visible grooves or scoring on the rotor face
• The car pulling to one side when braking, which can mean uneven pad wear or a sticking caliper
• A brake fluid level that has dropped, which can mean worn pads, or a leak

What you can check yourself

1. Look at the pad thickness through the wheel spokes, where you can see it.
2. Look at the face of the rotor. Light surface rust after the car has been sitting is normal and usually clears after a few gentle stops. Grooves or scoring are not normal.
3. Listen when you brake. Note whether a squeal happens every time or only now and then, and whether it has turned into grinding.
4. Check the brake fluid level against the min and max markings. A level that has dropped can mean worn pads, or a leak.
5. When you book, describe exactly what you notice: a noise, a pulse in the pedal, or the car pulling to one side. Ask for the rotors to be checked when the pads are replaced.
6. On an electric or hybrid car, look at the rotor face, not just the pad thickness.

Pads, rotors, or both?

• A consistent squeal or the pad wear light, and a smooth pedal: the pads are near their limit. Book within a couple of weeks, and have the rotors checked when the pads are changed.
• Grinding or metal on metal: pad material likely gone, so get it checked immediately. By then it is often already into the rotor.
• A pulse or vibration in the pedal during normal braking: usually uneven rotor thickness, not the pads, so have the rotors inspected.
• Minor surface wear or light rust on a rotor: can sometimes be resurfaced, as long as it stays above its minimum thickness specification.
• Grooves or scoring on a rotor: can come from pads worn to bare metal, so the rotors need inspecting along with the pads.
• Electric or hybrid car, plenty of pad left but rough braking: rusted or scaled rotors from regenerative braking. The pads are the part that lasts, the rotors are the part that fails.

What people get wrong

That brakes are due at a set mileage. Pads and rotors are best judged by their actual physical condition rather than a fixed schedule, because wear depends heavily on driving style, road conditions and climate. On an electric car it turns around completely: it is entirely normal to reach a high mileage on the original pads, and judging the brakes by pad thickness alone misses the rotors, which rust instead of wearing.

When to leave it to a workshop

Looking at the pad thickness and the rotor face, and describing a noise, a pulse or a pull accurately, is reasonable to do yourself. Replacing pads and rotors is not: torque specs and proper seating matter for safety, and brake work should be done by a qualified technician unless you have the specific training, tools and experience to do it safely.

Grinding or a soft, spongy pedal means get it checked immediately. A consistent squeal, a pulsing pedal or pulling to one side means book a service soon. If your brakes feel unsafe, have them inspected before driving further.

Read next

• Brake pad wear light: how long can you wait?
• Brakes squealing or grinding: what the noise means
• Car shakes when braking: this is the usual cause

This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.