Tyres can become damaged for a variety of reasons, and it can happen without the driver being immediately aware there's a problem. The most common types of damage are punctures, cuts, impacts, cracks, bulges and irregular wear. In this section, we'll explain the signs and symptoms to help you diagnose the issue, plus some useful tips on how to prevent them.
There are several types of irregular wear, the most typical variations being heel and toe wear, one-sided wear, and centre wear. Here we explain how and why they occur.
a. Heel and toe wear
Heel and toe wear is a pattern caused by normal usage and suspension settings. It's the outwardly visible (and audible) manifestation of various distortional forces at work on the tread. To explain further, let's dive a little deeper into the design of the tread.
Tread grooves and sipes are essential in ensuring safety on wet and flooded roads. With low-profile tyres in particular, a higher percentage of tread void is necessary to displace the water and to improve protection against aquaplaning. Cross-grooves for water drainage take the form of freestanding blocks in the shoulder area. These shoulder blocks can wear into a heel and toe pattern as a result of a rolling movement under certain operating conditions.
These operating conditions include:
As the tyre rolls along the road, the freestanding blocks deform as they get closer to the contact patch of the tyre, and they compress as they touch the tarmac. After they lose road contact, however, the blocks snap back into their original shape, rubbing the surface of the road as they do so. The result is wear on the block run-out edge and is more likely to appear on non-driven wheels.
A minor amount of heel and toe wear is reasonable and has no discernible effect on driving comfort. But if the wear is more extensive, more specific issues could be to blame, including improper inflation, excessive toe-in and low-wear applications.
b. Centre wear
You will find this wear pattern on the driven wheels of high-power cars. High torque levels generated during strong acceleration, in stop-start urban traffic or when accelerating away from traffic lights can quickly increase wear of the tread in the centre of the tyre. Even today’s mid-range vehicles have modern engines that can generate high levels of torque and are capable of producing high degrees of slip.
c. One-sided wear
The biggest cause of one-sided wear is incorrect axle geometry. Deviations from the standard specification can develop over time and are the result of, for example, mounting a kerb.
Lowering the height of a vehicle in conjunction with low-profile tyres can also negatively affect wheel alignment. During driving, modified suspension arms tend to cause the alignment of the wheels to deviate from the specified position. The problem can catch drivers unaware, because wheel alignment values can still be found to be within tolerance limits when measured in a static position on an axle measurement bench. But the manufacturer’s alignment data applies to vehicles as delivered and may not necessarily apply to customised cars. Thus, the result may be an increase in non-uniform tread wear.
If a vehicle’s wheels are misaligned, a qualified specialist can correct the deviation by realigning them.
An impact break is damage inflicted on the carcass (the casing of the tyre) after the tyre comes into contact with certain obstacles. A pronounced external bulge on the sidewall of the tyre indicates destroyed cords inside the carcass.
Damage of this kind is usually caused by driving over objects – like kerbs or speed bumps – at excessive speed or at the wrong angle, overstressing the carcass and causing individual cords to break. The exact extent of the damage will depend on the speed and angle of impact, and the size of the obstacle. Careful motorists are usually able to avoid this type of damage, unless an obstacle suddenly appears in front of them and they can’t steer around it.
Ignoring such damage increases the risk of tyre failure at some point in the future, either delamination of the tread and plies or disintegration of the tyre sidewall.
An impact break is sometimes confused with a sidewall indentation, but they are not the same thing. As we explain below, dimples or indentations in the sidewall are not cause for alarm.
A tyre sidewall is not always perfectly even; sometimes there will be dimples and indentations that may require a more detailed inspection to determine their cause. The essential thing to know is that indentations are harmless and aren’t detrimental to either driving or safety characteristics. The dimples are superficial.
Indentations in the tyre are best illustrated if you imagine tying a string around an inflated balloon and then gently pulling the string tighter. If the balloon is the tyre, the string is the embedded carcass cords, which are concealed by the rubber. These cords provide the tyre with its strength and stability, and transfer steering and braking forces while driving.
During manufacture of a tyre – or rather when constructing the carcass, to which the steel belt and the tread are attached – there are often one or two overlaps in the carcass. It’s this overlap that is sometimes visible as an indentation after the tyre is fitted and inflated.
But if you’re in any doubt, have the sidewall indentations checked by a qualified tyre specialist.
Cuts are the result of external influences like bad road conditions, protruding bodywork parts or sharp, foreign objects such as stones or glass. If you discover damage in the form of a cut on the tyre surface, you should visit your local tyre retailer and have your tyres immediately checked by a professional.
Punctures are the consequence of sharp objects on the road – for example, nails, screws or broken glass – that pierce through the surface of the tyre. If the puncture is deep enough, the tyre could begin to lose air pressure. If you find that one or more of your tyres are continuously losing pressure, or if you discover a nail or screw embedded in the tread, then visit your local tyre specialist as soon as possible to have them repaired.
Change the position of the tyres on the car at regular intervals (unless otherwise recommended by the vehicle manufacturer) to promote even tyre wear. The position of the tyres should be rotated, for example, when making the seasonal transition between summer and winter tyres.
By swapping the wheels from the driven to the non-driven axle on a regular basis, drivers can expect to have a uniform pattern of wear on all tyres. But as always, please observe the recommendations provided by the vehicle manufacturer.
If you find yourself in a situation where you have to drive over an obstacle in the road, approach it slowly and as close to perpendicular as possible. Afterwards, check your tyres for exterior damage such as cuts, cracks or bulges. Also, avoid driving aggressively on unpaved roads.