In the UK, the minimum legal tread depth (the height of the side of the tread above the base of the tyre) is 1.6mm across the central three quarters of the tyre. When new, a typical tyre has 8mm of tread depth.
However, manufacturers and road safety organisations recommend a minimum tread depth of 3mm. A low tread depth dramatically increases the distance needed to stop in wet weather. With 3mm, from 50mph to rest takes 113m but with 1.6mm this increases to 151m. Also, if below the legal level, you can be fined up to £2,500 per tyre – and receive penalty points on your licence.
The widely accepted way to test your tread depth is to insert a 20p coin at different points across the tread pattern and around the circumference. If any of the coin’s rim is visible, the tyre is likely to have to be changed.
How long should a tyre last?
This depends on how the car is driven, how the tyres are maintained and also the quality of the tyres. According to the AA, under normal driving conditions, you should get a minimum of 20,000 miles out of front tyres on a front-wheel-drive car (common for most cars). For rear tyres, it can be double that – around 40,000 miles.
All of the above applies to petrol and diesel cars. Do heavier, electric cars will wear out their tyres sooner? No. Their tyres are designed specifically for the extra battery weight with a specific rubber compound, greater sidewall, tread and groove strength. Kwik Fit says that according to recent studies, conventional tyres actually wear down 30% quicker than their electric vehicle counterparts.
Under-inflation will damage the structure of a tyre but over-inflated tyres will wear out sooner. They have a smaller contact area with the road, leading to increased stopping distance and reduced grip and also get a lot more wear across the central part of the tyre, leading to a shorter lifespan.
Assuming they are all set to the same correct pressure and are correctly aligned; tyres will wear out at the same rate according to whether they are the front pair or the rear.
If the engine drives the front wheels, the fronts will wear out sooner as they are both pulling the car along and being turned for steering and parking. Front tyres in general can also wear out more quickly due to wheel alignment problems where the car does not run straight because the steering and suspension has taken a knock.
On rear-drive cars there’s no steering (apart from some cars which have limited rear-steering) so less wear. On four-wheel drive cars the front set can still wear faster than the rears.
If the front wheels are out of alignment, typically having been knocked against a kerb, they will wear more quickly either on the outer or inner edges. This can also happen when cars are customised by their owners to lower the ride height by modifying the suspension. A specialist will need to re-align the tyres.
Should you rotate your car tyres?
In the days when many people did their own car maintenance, it was common to ‘rotate’ the front and back set of wheels to even out tyre wear, but few of us will probably do this now.
Tyre maker Pirelli says that under normal driving conditions, tyres should be rotated every 5,000 to 8,000 miles. If you have experienced alignment issues, balance problems or other tyre damage, it is best to also rotate your tyres when you fix this issue.
The tyres must be rotated in a set combination, not randomly. The best pattern for your vehicle will depend on its drive train. For example, for front-wheel drive vehicles an X-pattern where each tyre moves diagonally across.
This, however, assumes that your tyres are the same size for both front and rear. Your tyres also need to be ‘unidirectional’, meaning they can be fitted to either left or right wheels, if you’re swapping them from one side of the car to the other. ‘Directional’ tyres can be rotated front to rear on the same side of the car, as long as they are the same size for both front and rear.
Most cars run unidrectional tyres that are the same size all round, so any tyre can be mounted to any wheel and go on any corner of the car. However, some performance cars may have rear wheels that are larger and/or wider than the fronts, so you can’t rotate them. Directional tyre treads were popular on high-performance cars in the 1980s and 1990s, but are less common today.
Are your tyres too old?
If your vehicle doesn’t get driven much, it’s possible for the tyres to need replacing due to ageing rather than wearing out. Age-related damage is usually more common on caravan or trailer tyres, especially if left outside in the sun and rain.
The AA advises checking for signs of cracking on the sidewalls of tyres 4 or 5 years old if your car’s parked outside. You can find out how old your tyres are by checking for a code on the side of the tyre.
At the end of the DOT sequence of numbers there will be a 4 digit number code. For example, 1018 means the 10th week of 2018. Tyres over ten years old at the time of an MOT test will be failed if they are on any front steered axle.
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