Why is my car shaking? What the vibration tells you

When does it shake?

Where you feel it also matters: the steering wheel, the seat, the pedals and the floor pan each point somewhere different. Note that detail before you call anyone.

• Only when the car is stopped, in gear or in park — and it smooths out once you accelerate.
• Only at a particular speed range, usually on the highway, and it comes and goes.
• While braking, often worse at higher speed or downhill.
• While accelerating, sometimes with a clunk or a pull to one side.
• All the time, and it gets worse the faster you go.

What each pattern tends to point at

These are directions to test, not conclusions. Two cars with the same description can have entirely different causes, which is why the questions matter more than the first guess.

• Idle-only shaking that clears at speed is usually about how the engine is running — ignition, fuel, a vacuum leak, or a worn engine or transmission mount.
• A narrow speed range, worse at highway speed, is often wheel or tyre related: balance, a bent wheel, a tyre with a shifted belt, or uneven wear.
• Shaking under braking usually points at brake rotors, pads or hardware rather than the engine.
• Shaking under acceleration, especially with a noise or a pull, can be driveline — CV joints, half shafts or mounts.
• Constant shaking that worsens with speed can be a tyre, wheel bearing or suspension component.

What to note before you ask anyone

• The speed range where it happens, and whether it stops above or below it.
• Whether the steering wheel, the seat or the pedals shake most.
• Whether it changes with engine temperature, gear, or load.
• Tyre pressures and any recent tyre, brake or suspension work.
• Whether anything else changed at the same time — a noise, a warning light, a pull.