Why does my car shake when I brake?

A vibration under braking is never harmless

If you feel shaking in the steering wheel, the brake pedal or the chassis when you brake, something is wrong with your braking system. Brakes are the most critical safety system on your vehicle, so this symptom deserves prompt attention.

Cause #1: warped brake rotors

This is the most common cause. A "warped" rotor is no longer perfectly flat: it has a slight wave-shaped distortion. When the pads rub against that uneven surface, they create a rhythmic vibration that travels into the pedal and the steering wheel.

• ✓The vibration gets stronger the faster you are braking from
• ✓The steering wheel wobbles slightly from left to right
• ✓You feel a pulsing in the pedal
• ✓Often caused by repeated hard braking or cold water splashed onto hot rotors

Cause #2: worn or glazed pads

Brake pads whose friction material is used up, or whose surface has glazed from overheating, no longer grip the rotor evenly. The result is a vibration, often with a grinding or squealing noise.

• ✓Metallic grinding when braking (the wear indicator touching the rotor)
• ✓Longer stopping distance
• ✓A pedal that travels lower than before

Cause #3: a suspension or wheel bearing problem

If the vibrations are there even without braking but get worse when you brake, the problem may come from the shocks, the ball joints or a failing wheel bearing. In that case the vibrations are often present at high speed and are not limited to braking.

What should you actually do?

Have your braking system inspected by a mechanic as soon as possible. A visual inspection of the rotors and pads takes about 20 minutes and pinpoints the cause. The cost of an inspection is nothing compared with the risk of brakes that fail.