The depth of tread on a tyre is very important, because it ensures the car grips the road as efficiently as possible. The depth is considered to be so important that there are strict laws regarding the minimum amount of tread that must be on the tyre. Failure to meet these requirements can lead to prosecution and a hefty fine. Also, if the vehicle is involved in an accident and has defective tyres the owner's insurance company may well decline to provide cover. That is why it is so important that owners regularly measure their car's tyre tread to ensure they comply with the law.
In the United Kingdom and Europe the legal minimum depth for tyre tread is 1.6mm. This must be continuous, around at least 75 per cent of the tyre. It should also be remembered that the tyre tread regulations apply to any spare wheel carried on the vehicle.
1.6mm is the absolute minimum acceptable. With further wear and tear, especially if the vehicle covers big mileage, it will not be too long before the depth of tread contravenes the law. In fact it is recommended that motorists replace tyres once the depth reaches 3mm.
Measuring the tread on tyres is quite simple to do. While some people use the edge of a 20p coin as a rough guide, there are gauges available that will give a far more precise measurement. Motorists are advised to purchase one of these devices, some of which can also be used to measure tyre pressure.
When measuring the tread depth the vehicle should be parked on a flat and even surface, in a safe place away from moving traffic. Using the tyre tread gauge, the main tread grooves should be checked in several places around the tyre. It is important to read the instructions that come with the gauge to ensure it is used correctly.
Tyres also have what are known as tread wear indicators, which are moulded into the base of the main grooves. An indication that the tyres have reached the minimum depth becomes apparent when the tread level reaches the same level as these indicators. However, if when checking the tread, it is found they have worn down to 3mm or less it is best to take the car to a local tyre centre to have replacements fitted.