How to read tyre wear
Updated 18 Sept 20266 minute readBy AutoworkX, Coburg North
Tyres wear in the shape of the fault that is causing it. Both edges gone means underinflation, a worn centre strip means overinflation, one edge means alignment, and scalloped patches mean suspension. Read the pattern at the next fuel stop and you fix a cheap cause instead of buying tyres early and buying them again.
How to check them in two minutes
Park on level ground with the wheels straight and the car cold. Look across the whole width of each tread, not just the part facing you, and run a hand across it in both directions. Uneven wear is often easier to feel than to see, and a tread that feels smooth one way and sharp the other is telling you something on its own.
- Find the tread wear indicators, the small raised bars sitting in the bottom of the main grooves
- Tread level with those bars means the tyre is at the legal limit of 1.5 millimetres and is finished
- Compare the inner edge with the outer edge, and the left of the car with the right
- Check the pressures cold, against the placard in the door opening or the fuel flap, not against the number on the tyre wall
- Look for cuts, bulges in the sidewall, embedded screws and cracking in the rubber
- Check the spare while you are there, because a flat spare is only discovered at the worst moment
The number moulded into the sidewall is the maximum the tyre can hold, not the pressure your car wants. The placard on the car is the figure to use.
What each pattern is telling you
| What you see | Likely cause | What it needs |
|---|---|---|
| Both outer edges worn, centre still good | Running underinflated | Set the pressures cold and check for a slow leak or a valve fault |
| Centre strip worn, both edges still good | Running overinflated | Set the pressures to the placard figure and recheck in a fortnight |
| One edge worn, usually the inner | Wheel alignment out, commonly camber or a tired bush | Alignment check, and inspect the suspension before it is set |
| Feathered edges, sharp one way and smooth the other | Toe setting out | Wheel alignment, sooner rather than later |
| Scalloped or cupped patches around the tyre | Worn shock absorbers or loose steering components | Suspension and steering inspection before new tyres go on |
| One flat patch | A locked wheel or a braking fault | Brake inspection, and the tyre usually needs replacing |
The pattern is the diagnosis. Replacing tyres without fixing what wore them out simply restarts the clock, and the new set goes the same way in the same number of kilometres.
Why this is worth two minutes a month
Tread depth is what clears water out from under the tyre. As the grooves shallow, the speed at which the tyre can do that falls, so wet braking distances stretch long before the tyre reaches the legal limit, and a tyre that is still legal can already be well down on wet grip.
Underinflation costs money in three directions at once. The tyre wears at its shoulders, the engine works harder against the extra rolling resistance, and the sidewall flexes and heats until it is at risk of failing at highway speed. Pressures are free to fix and they drift with the seasons, so a cold check once a month costs nothing and takes two minutes.
Rotation, alignment and balance are three different jobs
People use the three words as if they were one service. They fix different problems, and knowing which you need saves a wasted booking.
- Rotation moves the tyres between positions so that the driven wheels do not wear out ahead of the others
- Alignment sets the angles the wheels sit at, which is what stops a tyre wearing on one edge or pulling the car sideways
- Balancing corrects the weight distribution of the wheel and tyre together, which is what removes a vibration at speed
A wobble through the steering wheel at highway speed is usually balance. A car that drifts towards the kerb on a flat road, or eats one edge of a front tyre, is usually alignment. A tyre that has worn out well ahead of its pair is a rotation and pressure story.
Fix the cause before you buy the rubber
Treat the tread as a report on the rest of the car. If the wear is even across the tyre and across the axle, the car is set up correctly and you are simply buying tyres when they are used up. Anything else is the car asking for a check that costs far less than a set of tyres.
- Even wear all round: keep checking pressures and replace at the wear bars
- Edge or centre wear: pressures first, then a recheck in a fortnight to see whether they are holding
- One edge only, or feathering: book an alignment and have the suspension looked at first
- Cupping or a vibration: suspension and steering inspection before you spend on rubber
- Any bulge, deep cut or exposed cord: fit the spare and get the tyre replaced, not repaired
Book before the wear bars, not after
Book when the tread is getting close to the wear bars, when one tyre is wearing differently from its pair, after hitting a decent pothole or kerb, or when the steering has gone vibrating or off centre. Book straight away for a sidewall bulge, since that is a failure waiting for a hot day.
A photo of the worn tread and one of the placard in the door opening is usually enough to start with. We check the wear, the pressures and the suspension before quoting anything, so you are not buying tyres that a bush or an alignment is going to ruin.