Car shakes when braking: this is the usual cause
If it only shakes when you brake, the cause is almost always in the brakes themselves, and most often in the rotors. A pulsing or vibrating pedal usually means a rotor has developed uneven thickness, often from repeated heat cycles.
Can you keep driving?
In the short term, yes: a pulsing pedal means get it checked soon. Grinding or a soft pedal is different, and needs checking immediately.
What the pulse actually means
A rotor is meant to be flat and even. Once it develops uneven thickness, often called warping, the pads grip it unevenly as it turns, and you feel that as a pulse in the pedal.
How the brakes stop the car
When you press the pedal, the calipers squeeze the pads against the rotors, and the friction turns the car's momentum into heat. Every rotor also has a minimum thickness, and that measurement decides what can be done about it.
Common causes
- Rotors with uneven thickness, often from repeated heat cycles
- Light surface rust after the car has been sitting, usually temporary
- Pads worn down to bare metal, which can score the rotor
- Uneven pad wear or a sticking caliper, which also pulls the car to one side
- On an electric car, rusted or scaled rotors from barely using the friction brakes
What to do now
- Note whether it is a pulse in the pedal, a grinding noise, or the car pulling to one side.
- If the car has been sitting, brake gently a few times and see whether it clears. Light surface rust usually does.
- Look at the pad thickness through the wheel spokes if you can see it.
- On an electric car, look at the rotor face as well as the pads.
- Book an inspection, and ask for the rotors to be checked, not just the pads.
Pulse, grind, or ABS?
- A pulse or vibration in the pedal during normal braking: rotors with uneven thickness.
- Rapid pulsing with a grinding or clicking noise under hard braking: ABS working, which is normal.
- Grinding or metal on metal: pad material likely gone, get it checked immediately.
- Rough only for the first few stops after sitting: light surface rust, normally clears on its own.
- Electric car, little pad wear but rough braking: rusted or scaled rotors from regenerative braking.
- Shaking even when you are not braking: tire balance or suspension, not the brakes.
What people often get wrong
That warped rotors always have to be replaced. A rotor with minor wear or light rust can sometimes be resurfaced. Whether that is safe depends on its minimum thickness specification, which is measured, not judged by how the pedal feels.
When the car must go to a workshop
A grinding or metal on metal sound, a soft or spongy pedal, or a brake warning light with a pedal that feels different: get it checked immediately.
Read next
- Brake warning light: check this first
- Brake pad wear light: how long can you wait?
- Car shakes while driving: what is causing it
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.
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