Road safety begins with a safe vehicle. Good driver should be aware that even the slightest negligence regarding condition of the vehicle can have serious consequences.
Tyres are often neglected yet they are one of the most important elements of the car and the only one actually touching the road. Therefore their impact on the comfort and safety is essential. No matter how good and powerful the car is, the only contact with the road to transmit such power is made through the tyres. How acceleration is transmitted without skidding when you start, how a sharp curve is taken without squealing noise or how finally the car stops within a safe short distance, it all depends on the tyre quality and maintenance condition. Tyre life varies according to its type and brand, but in all cases any tyre will wear much faster and have a shorter life with unadequate exploitation conditions. Tyres should be monitored on a regular basis by the driver to keep right air pressure, to remove any stones or sharp object suck there or to make sure there is no cut or damage. Tyre service professionals should also monitor it from time to time as they could detect other issues like irregular wear and then propose proper maintenance to solve the issue.
It is also essential to check the tread depth. Polish Road Traffic Act clearly states that no vehicle should be equipped with a tyre which tread depth is less than 1.6 mm at any point on the thread of the tyre. This minimum level is indicated by several series of bulges in the thread grooves. This is the absolute legal minimum, but you must be aware that for a greater safety in rainy or snowy roads a tread depth of at least 3 mm in case of summer tyres and 4 mm in winter is highly recommended. The lower the tread, the less it is possible for the tyre tread to drain water and slush.
UK’s Motor Industry Research Association research shows that the average braking distance at the speed of 80 km/h on wet surface for tyres with a tread depth of 8 mm is 25.9 meters, with 3 mm it is 31.7 meters or +22%, while at 1.6 mm it is up to 39.5 meters or +52%. [1]
In addition, at higher speed levels aquaplaning may appear, which is complete loss of adhesion after entering the water. The less tread, the greater the likelihood of its occurrence.
- Not everyone remembers that not keeping the minimum tread depth has legal consequences and that the insurer may refuse to pay compensation or costs of repairs in the event of a collision or accident, if it appears that the condition of the tread is main cause. Therefore, we recommend any driver to also control tread depth when making periodic check of the tyre pressure. It should become a monthly habit - says Piotr Sarnecki, Director General of the Polish Tyre Industry Association.
Also people who drive infrequently and do not wear the tyre so fast should nevertheless regularly check the tyres. Attention should then be paid to any cracks, blisters, delamination, which may indicate some progressive damage to the tyre.
As already mentioned in some cases the tread may not wear equally or show some kind of serration. It is usually the result of some mechanical problem with the car or the rim like improper state of suspension geometry, bad bearing or broken dumper. That is why the wear level should always be measured in several places on the tyre. For easier control drivers can use the existing wear indicators, the bulges in the middle of the tread grooves which position is signaled with a triangle, brand logotype or TWI letters (Tread Wear Index), located on the sidewall. Any tyre wear to the level of any of these indicators means that the tyre is worn out and should be replaced.
How to measure tread depth?
First of all, vehicle should be parked on a flat and level ground, the steering wheel should be turned maximum to the left or right. It would be perfect if the driver had a special device to measure the tread depth. If not, just use a match, a tooth pick or a ruler to check and measure thread depth. In Poland an even easier way is to use a coin. It should be inserted down with the crown of the eagle going first. If the whole crown is still visible then replace the tyre. Of course this is not a very accurate method and it is always better to have a proper check by a tyre service.
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