How to know when you need new tyres?

By Julia Freeman

Your tyres are the only part of the car in contact with the road surface so play an enormous part in the safe running of your vehicle. Although many drivers believe they know intuitively when their tyres need replacing, this is always a dangerous assumption to make. Your tyres could develop a problem at any time and checking them monthly is essential.

car driving along road

Tyre wear markings

Most modern car tyres have a wear indicator set into the tread pattern. The letters “TWI” can often be found on the tyre shoulder and this is to show you which part of the tyre to search for the wear indicator. The letters “TWI” are not the wear indicator and being able to see them does not mean your tyres are not worn! The wear indicators are (usually) little raised ridges inside the grooves. When those ridges are the same height as the rest of the tyre it indicates you are at the legal limit (1.6mm).
TWI marks may not be present or easy to see – it depends on the tread pattern – nor are they a fully reliable guide whether your tyres are legal or safe. By law, the tyre tread must be a minimum of 1.6mm across the contact area of the tyre but many car faults – such as incorrect inflation and wheel alignment issues – can result in uneven wear. As such, TWI ridges are a guide not a guarantee that a tyre is legal.

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Nor is a legal tyre necessarily safe: car safety experts say the safe limit is closer to 3mm and you should consider new tyres well before they are illegal.
If you have an accident and go to court, illegal tyres can result in a fine of £2,500 and 3 points on your license – per tyre – and your insurance will be invalidated. Bridgestone are lobbying the government to introduce on-the-spot fines for worn tyres.

The 20p test

There are probably twenty versions of “the 20p test” because nobody remembers it properly. The rim on a 20p is not 1.6mm, it is 2.7mm – which makes it a completely arbitrary way to “measure” tread depth. However, if you place a 20p piece into the tread grooves of your tyres and you can still see any of the rim you should definitely visit a garage to have your tyres properly examined.

You can buy a proper tyre gauge from any good motoring accessory supplier, but the most sensible way to check your tread depth is by asking Protyre’s tyre professionals for a free tyre check.

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Motorcycle tyres

Motorcycles and mopeds under 50cc must have the tread pattern at least visible everywhere on the tyre. Motorcycles over 50cc must additionally have a tread depth of at least 1mm across 75% of the breadth of the tyre, around the entire circumference. Again however, legal tread depth does not guarantee that tyres are safe.

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Book with Protyre

Don’t wait until you “think” your tyres need replacing, book a free tyre safety check with Protyre today. Our tyre professionals also inspect for damage, perishing and uneven wear to help give you peace of mind. When you are ready, we have a great range of Bridgestone, Pirelli, Continental, Michelin tyres, as well as several budget friendly brands, at every Protyre garage.

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About the author

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By Julia Freeman
Julia is Head of Retail Marketing for Protyre and loves engaging with customers and the business as a whole to make sure Protyre is more than just a local garage.
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