How to diagnose wheel alignment issues before it’s too late

Neutral camber

For most road cars, this is the preferred set-up. In effect, the wheel remains perpendicular to the road, with only a small amount of camber change caused by cornering load during cornering. Assuming all is well in the car’s alignment, then you should see even wear across the tyre’s tread.

Positive camber

As its name suggests, positive camber is the opposite of negative camber. In this set-up scenario, the top of the angle outwards and the bottom inwards. It’s the sort of arrangement you’ll spot on older, usually vintage machines. This is because it helps make the handling a little more predictable, even if it actively reduces grip and cornering forces grow.

Simplified, positive camber on the front wheels will promote severe early onset understeer, while used at the rear if promotes oversteer. While this is usually engineered into the design, sometimes it can be an undesirable side effect. Most famously, cars with swing axle rear suspension (early rear-engined Skodas or the Mercedes 300SL Gullwing) suffer from sudden positive camber at the rear, the wheels effectively tucking under themselves under big cornering loads which results in hairy, snap oversteer.

Again, large doses of positive camber are rare on modern road cars, but if you spot excessive wear to the outside edge of a wheel, then this could be the culprit (and once again worn suspension could be the issue.

Caster

In fairness, changes in caster angle are unlikely to result in extra or unusual tyre wear, as it doesn’t directly affect the way the tread and road surface interact. Look at the car side on and imagine a line going straight through the front wheel, from top to bottom - this is essentially the caster angle.

As with camber, there are negative, positive and neutral (zero) states of angle for the caster, with each having an effect on the steering. 

Negative caster

This set-up is similar to that used on a shopping trolley, making the steering very easy to turn. However, the downside is that its effects are amplified during braking, making the steering more sensitive and the car feel less stable (imagine that trolley with one of its trademark wobbly wheels flailing around as you push it).

Zero caster 

Technically the purest set-up (it was used by Citroen in the DS, GS and CX), as it reduces kingpin torque (effective steering effort) at the limit of grip, giving the driver a clear message of how much adhesion they have left. However, while not as unstable as negative caster, it does require greater steering correction when at a steady state cruise, making it less relaxing in everyday use.

Positive caster

Most road cars have a little bit of positive camber dialled-in to their factory settings, largely because it creates what's known as ‘self-aligning torque’. To you and me, that’s self centering. It’s what creates strong straightline stability and what allows the steering to spin itself straight when you let go of the wheel (you shouldn’t really do this, obviously) when, say, existing a junction.

Interestingly, this set-up results in the front of the car being ‘jacked-up’ as steering lock is applied (go outside and get an assistant to twirl the steering of your car from lock-to-lock while stationary and you’ll spot the nose subtly lifting). On the plus side, this effect when combined with cornering loads on the move promotes a little negative camber, helping to improve grip.

Toe

The last piece of the alignment puzzle is toe, and this is the one most likely to cause you issues if it’s not where it should be. While camber and caster adjustment  is available on some cars (usually high-end performance machines and those with independent rear suspension), almost every model on the road can have its toe fiddled with.

Essentially, it’s limited to the front wheels (although cars with multi-link rear axles will have an element of toe adjustment), and is commonly known as ‘tracking’. It’s the set-up that dictates what angle the wheels are pointing in, and how its set-up will affect the way the car handles and the way the tyres wear. 

If the toe angle falls out of factory specification, then you might notice the car pulls to the left or right even when driving in a straight line, while the steering wheel itself might be off centre. As with camber and caster, there are three states of toe: toe-out, toe-in and zero-toe. 

Toe-out

In this state, the back edge of each tyre is effectively closer together than the front. This creates a stronger turn in grip but comes at the expense of stability, with the steering wheels likely to pull the car left or right over uneven surfaces. If the inside edge of the front tyres is worn, then it’s likely to be a result of excessive toe-out.

Toe-in

With toe-in, the front edge of each front wheel is closer together than the back, creating a sort of pigeon-toed stance. This arrangement loses some of the positive turn-in characteristics of toe-out and the stronger grip, trading it for the reassurance of improved straightline stability. If there is excessive toe-in on the alignment, then you’re likely to spot as the outside edge of the front tyre will wear more quickly.

Zero-toe

Like zero caster and camber, this is theoretically the purest set-up (once again, those pioneering Citroen’s featured it all those years ago, helped by the geometry-maintaining characteristics of their self-levelling suspension), yet very few cars feature it. In reality, the bumpy and cambered nature of roads, plus the varying in-car loads, means the car would feel far too sensitive, the toe characteristics changing subtly in line with the topography.

Alignment

Ultimately, all of these factors fall under the umbrella term of ‘alignment’. More importantly, if you want to keep your tyres in tip-top shape then it’s important you get the suspension geometry checked on a regular basis, especially if you’ve accidentally hit a large pothole or glanced a kerb.