In a previous article, we looked at the European car and equipment requirements for when you are driving through various countries. While this did include a look at the UK, what are the actual tyre laws and requirements at large? For regular residents of the country, there are a few more laws and regulations that need to be abided by.
UK tyre laws & legal requirements on the road
When it comes to the qualities of a car tyre, there are a few areas which are important in UK law, primarily the tread depth, speed and load indexes, as well as the quality or stability of the tyre. Here, we will break down the various UK tyre laws and legal requirements that you, as the driver, need to be aware of.
Tread depth
Legally, all cars on UK roads require a tread depth of 1.6 mm at the very minimum. This needs to be in a complete band around the tyre - there should be no points where the tread depth goes below this value.
Because of this importance - and the fact that 1.6 mm is a legal requirement in many countries - tyre manufacturer’s often incorporate features to indicate the level of wear and tear on your tyre. A mould bar is a line of rubber found 1.6 mm into the tread.
although it is the minimum required, a tread depth above 1.6 mm is recommended for better grip and performance.
As the tyres wear down, this becomes more visible and, if it’s flush with the outer surface of the tread, you have reached 1.6 mm and should immediately buy new car tyres. Of course, for safety reasons, it is always recommended you do this before reaching 1.6 mm, as a thicker tread offers better grip, performance and resistance from aquaplaning.
A Tread Wear Indicator (TWI) is a similar concept, using a specific marking within the grooves of the tyre. Just like the mould bars, this becomes more visible as the tread depth is worn a way, acting as a reliable indicator.
Speed and load indexes
As previously discussed, speed and load indexes inform you of the maximum speed and load, respectively, that your tyres can take. For load indexes, you must use the minimum values given in the vehicle’s manual - as decided by the manufacturer. You cannot use a lower value.
As for the speed index, this must match the maximum speed of the vehicle, not the national speed limit of 70 mph. This means looking through the vehicle’s manual to find the official top speed and ensuring you have the subsequent matching tyres. For example, while any tyre with a tyre speed index over L (75 mph) is suitable for the purposes of driving under the national speed limit, if your vehicle has a top speed of 150 mph, than you would need tyres with a W (168 mph) rating or higher.
Spare tyres
Spare tyres are not a legal requirement in the UK. Even if you have one, it does not need to meet any regulations, so long as it is not being used. However, the moment such a spare tyre is put onto a wheel and used, it must meet the typical requirements for a roadworthy tyre.
Duty of maintenance
As the owner and driver of the vehicle, you have the ongoing legal obligations to maintain your tyres. These must be fit for purpose all points. This means ensuring the tread is the right depth - above 1.6 mm - as well as a few additional factors.
Your wheels should not have any lumps, bumps or other noticeable imperfections, as these can separate the structure and cause more dangerous driving. Even if a tyre has factory defects, it is up to you to either repair or replace this.
It is up to the driver to ensure the car tyres have a tread depth of 1.6 mm when on the road
Speaking of repairs, any cuts in the tyre can not exceed 25mm, or a tenth of the total width of the tyre. This is to ensure that such tears do not go deep enough to reach the inner tyre textile components, such as the cords. Exposing these can easily ruin the driving quality of the tyre, making them highly unsuitable.
Similarly, the tyre should be inflated in line with the vehicle manufacturer's specifications, as well as the recommended tyre pressure.
Implications of inappropriate tyres
Having the wrong tyres, or just tyres under the accepted level of roadworthiness, can have a number of implications. First of all, if the police inspect your car, you could be fined or have the car towed. An officer can issue you a fixed penalty notice on the spot, or even make a case for prosecution. At the most, a defective tyre can cost you as much as £2,500 in fines and 3 points on your license. For vehicles that can carry more than 8 people, or goods, this can be up to £5,000.
However, these charges apply per tyre, so the penalties will stack if more than one tyre is against UK regulations. It is also worth noting that both the driver and the vehicle’s owner, if they are different people, can be summoned under this process.
In the UK, the police can issue fines for inappropriate tyres.
Secondly, you will also have difficulty with your insurance company. Your insurance provider may argue that your car was not in the required standards to be on the road and, as such, is void from their policy. Because of this, it is always best to keep your insurance company informed of any changes, such as fitting new tyres, swapping to winter tyres and changing the tyre size.
Thirdly, your choice of tyres will also be tested and noted during various tests, such as getting an MOT for your vehicle. In short, an MOT inspects your car for its roadworthiness, which involves looking at the quality of the tyres. If your tyres have too thin a tread depth, have tears wider than allowed or are of an inappropriate size, speed or load index, the vehicle could potentially fail its MOT test. Again, the spare tyre (if applicable) does not count.
While many of these tyre laws and regulations offer a minimum requirement, it is always better to go above this. A thicker tread offers more control, for instance, and gives you more time to replace the tyre itself.