Alignment faults rarely announce themselves with a warning light, but show up as an off-centre steering wheel, a pull to one side, or early tyre wear. Here is what to look for.
The symptoms worth acting on
- the car pulls to one side on a flat, straight road;
- the steering wheel is not centred when the car is going straight;
- one edge of a tyre is wearing far faster than the rest;
- the tread feels feathered or scalloped when you run a hand across it;
- the car follows ruts and white lines rather than your steering — tramlining;
- the steering feels vague, or will not self-centre properly after a turn.
Any of these is worth checking, because the cost of ignoring them is paid in tyres. A geometry fault of a degree or two can halve the life of a tyre, and on a premium car that is a significant bill arriving early.
The three angles, in plain terms
| Angle | What it describes | What it does when wrong |
|---|---|---|
| Toe | Whether the wheels point slightly inwards or outwards, seen from above | The most common cause of rapid, feathered tyre wear; also affects straight-line stability |
| Camber | How far the wheel leans in or out at the top, seen from the front | Wears one edge of the tyre; if uneven side to side, the car pulls |
| Caster | The angle of the steering axis, seen from the side | Affects how the steering self-centres and how stable the car feels at speed; uneven caster causes a pull |
Why "tracking" is not the same thing
A two-wheel check — often called tracking — sets the front toe and leaves it there. The problem is that the front wheels are being set straight relative to the car's centre line, when what matters is where the rear axle is actually pointing. That direction is the thrust line, and if the rear is slightly out, setting the front to the centre line builds the error in: the car then needs a permanently off-centre steering wheel to travel straight, and both sets of tyres scrub.
A four-wheel alignment measures all four wheels and sets the front relative to the rear's real thrust line, correcting the rear where it is adjustable. On most modern cars it is the only version of the job worth paying for.
When to have it checked
- With new tyres. Fitting fresh tyres to a car with a geometry fault is the most expensive way to discover the fault.
- After a kerb strike or a bad pothole. One firm hit is enough to move a setting.
- After suspension or steering work. Replacing arms, bushes, springs, shock absorbers or track rod ends changes the geometry by definition.
- After lowering the car or changing wheel or tyre sizes. Ride height and geometry are related.
- After accident repair, however minor it looked.
- When the symptoms above appear, rather than after the tyres have gone.
While the tyres are off the car
Alignment and tyre condition are worth assessing together. The UK legal minimum tread depth for a car is 1.6mm, and it has to be met across the central three-quarters of the tread and around the entire circumference — the outer shoulders alone do not count. Driving on a tyre below that risks a fine of up to £2,500 and three penalty points per tyre. Many safety bodies suggest replacing at around 3mm rather than running to the limit, since wet braking falls away well before the legal minimum is reached.
Uneven wear is also evidence. A tyre worn on both edges but not the middle points at underinflation; worn in the middle only suggests overinflation; worn on one edge points at camber or toe. Balancing matters too — a wheel that is out of balance causes a vibration that rises and falls with speed, which is a different fault from a pull.
One thing to settle before the work
If your car has driver assistance systems, changing its geometry can mean those systems need recalibrating afterwards, because several of them are referenced to the thrust line you have just corrected. It is a question to ask before booking, not after. There is more in ADAS calibration: when your car needs it.
Mitsiland offers four-wheel alignment, tyre fitting and balancing, with ADAS calibration where the car calls for it, from our Denton workshop in Manchester. Call 0161 320 7788 if the car is pulling or chewing through tyres.
