What is wheel alignment and when does a car need it?

Alignment is the set of angles at which the wheels sit relative to the road and to each other. When those angles drift out of specification, the tyres are dragged rather than rolled, and they wear out quickly.

Three angles matter.

Toe is whether the wheels point slightly inward or outward when viewed from above. It is the angle most often out and the one that destroys tyres fastest — even a small error scrubs rubber away with every metre travelled.

Camber is the tilt of the wheel from vertical, viewed from the front. Negative camber, the top leaning inward, improves cornering grip but wears the inner edge.

Caster is the forward or backward tilt of the steering axis, viewed from the side. It affects straight-line stability and how strongly the wheel self-centres.

The usual causes of misalignment are impacts: potholes, kerbs, speed bumps taken quickly. It also follows naturally from worn suspension components, and from any suspension or steering work, which is why alignment should be checked after replacing such parts.

Symptoms worth acting on are uneven tyre wear — particularly one edge wearing faster than the rest — a steering wheel that sits off-centre when driving straight, the car drifting to one side on a level road, or steering that does not return to centre after a turn.

A drift alone is not conclusive. Road camber makes most roads drain toward the kerb, and uneven tyre pressures cause pulling too, so check pressures before paying for alignment.

Many garages offer a two-wheel alignment; four-wheel is more thorough and is what most modern cars need, since rear alignment affects how the car tracks.