What is tyre runout?

Radial runout

The distance from the centre of the wheel to the tread should be the same all the way round. With radial runout it is not, so the wheel bounces as it turns. This is the more common type, and you feel it as vibration that often travels up the steering column.

Lateral runout

The tread edge moves from side to side as the wheel turns, so the tyre is less supported at some points. The car can vibrate, wobble or drift from left to right at random, a bit like a trolley with a bad wheel.

Runout is often confused with poor tracking, but they are different problems. See 10 signs you need a wheel alignment.

• Impacts. Potholes, kerbs and collisions.
• Manufacturing. Poorly made tyres that missed quality control, or wheels made in low-grade moulds.
• Mounting. A tyre not seated properly on the rim, for example if the bead seating ring was not lubricated and the tyre mounted incorrectly.
• Flat spots. A flat patch where a tyre has stood in one position for a long time.

Have tyres fitted by a trained technician, rotated and inspected regularly, and check pressure and condition yourself. Check pressure when the tyres are cold, and look at the tread: the minimum is 1.6 mm across the central three-quarters of the tread and all the way round. See how often to check tyre pressure.

Wear indicators, small raised bars between the tread grooves, tell you when the tyre has worn down to replacement level. When you only replace two tyres, fit the new ones on the rear axle.

A technician looks for flat spots and measures runout with a dial indicator or runout gauge. Depending on the cause, the fix may be rebalancing the wheel with weights, or removing and refitting the tyre.

Runout tends to get worse over time, so do not ignore the signs. If you feel a vibration at speed, have it checked. We can look at it where you are: call us.