Do you know the law relating to car tyres?

You might think you know the law when it comes to the tyres on your car, but do you really know it as well as you think? If you don’t, ignorance is no excuse, and you can end up with fines and points on your licence. These penalties apply per tyre, so can soon mount up if you have 4 illegal tyres, as you could be fined £2500 and receive three penalty points on your licence for each illegal tyre.

Minimum depth

The legal limit for minimum depth of the tread is 1.6mm. This depth limit applies to the central three-quarters of the tyre, and all the way around it, so make sure you measure in different places. Although tyres typically wear from the middle, it is important to measure across the tyre, as factors such as bad tracking could mean that the outside wears more quickly than it should.

Don’t leave it until your tyres have gone down to 1.6mm depth before replacing them, as this is right on the limit and not only could you find yourself in trouble with the law, it means your car is borderline unsafe. Instead, get your tyres changed before they reach 2mm tread depth. A good rule of thumb is to keep a close eye on your tyres once the depth gets down to around 3mm. Depending on how much you drive, this could mean measuring them on a weekly or monthly basis.

Fit for purpose

You should also make sure that the tyres fitted to your vehicle are fit for purpose. Your vehicle handbook will tell you the type and size of tyre your car needs, and if there are any other special requirements depending on how you are using it (for example with heavy loads). You also need to follow your manufacturers guide for tyre pressure, which should be checked regularly from cold (i.e. before you have driven any distance).

Tyres that are structurally unsafe are also un-roadworthy in the eyes of the law, so look out for any lumps, bumps or tears. The law specifies that no cut or tear should exceed 25mm, or 10 percent of the width of the tyre if this is greater. The consequences of a tyre giving in when travelling at high speed can be severe, so it is not a risk worth taking.

Radial and cross-ply tyres

You can easily tell whether or not your tyres are radial or cross-ply by the number printed on the side of them. A radial tyre will have a number with an R in the middle of it, for example 750R16, whereas there a cross-ply tyre would have a number like 750-16.

As these tyres behave in totally opposite ways to one another (radial tyres have flexible side walls, whereas cross-ply tyres have rigid sidewalls), the law states that these not be fitted on opposite sides of the same axle. Although not usually recommended due to issues such as tyre wear and fuel economy, it is within the law to mix brands and patterns on the same axle, providing the construction type of both is the same.

Cars Service and Repairs