Why does my car hum when I drive?

A constant hum that rises with road speed (not engine speed) is almost always a wheel bearing or worn tyres.

Here's a quick, honest answer from a working UK mechanic — what causes it, what it costs to fix, and what to do next.

Is humming an MOT fail? — No — but the underlying cause (worn bearing, bald tyre) usually is.

Why does it only hum at certain speeds? — Tyres and bearings have resonant frequencies — a noise that peaks at 50 and 70 mph is normal for a worn tyre.

Bob's Mechanical Repairs — independent family-run garage in Birnam, Dunkeld, Perthshire. Call 01350 727 276 or email bob@bobsmechanicalrepairs.co.uk.