Why you should check the tyres when buying a used car

There are plenty of things to think about when buying a car, from checking its history to whether you can afford to run it. 

You should always check whether the previous owner has kept up with general maintenance. Looking over the tyres are an important aspect of checking over a used car and you need to see whether tyres meet the required legal limit of safety. If they’re not up to scratch you could be putting anyone in your car, and other road users, at risk.

And if you’re pulled over by the police and don’t have safe and legal tyres, you could also be slapped with a hefty fine for each one.

We’ve put together a quick guide to help answer any questions you might have – so you stay safe and avoid a costly mistake.

How do I check my tyre tread depth?

When a tyre is new, it’ll have about 8mm of tread. This is the depth of the grooves in the tyre, which help to channel water away from the surface and keep the tyre in contact with the road. As this wears down, it becomes less effective.

The legal limit is 1.6mm(in a continuous band around the central 3/4 of the tyre), though it’s recommended that you have new tyres fitted once you get to 2mm.

Checking how much tread is left is easy, and there a number of ways you can do it. The first is to find the treadwear indicators, which are raised areas built into the grooves. When the raised areas are level with the surface of the tyre, the tread has worn down to the legal limit and it’s time to get new ones.

As a quick guide you can also use a 20p coin. Simply place it, edge on, into the groove, and if the outer band of the coin is covered then the tyre is legal – but if it isn’t then the tread could be too low.

And finally, you can buy a tread depth gauge, which will tell you exactly how much tread is left. If the tread is low on the car, you might be able to negotiate a discount, request the seller replaces the tyres before you buy or factor the cost of changing the tyres after you buy.

How else can I check tyre roadworthiness?

It’s not just tread depth that can affect the safety of a tyre. The condition of the rubber is just as important.

When looking at the tread depth, make sure you also inspect the surface of the tyre to look for any cuts or bulges that could indicate the tyre is at risk of a blowout. Remember to check the inside of the tyre by running your palm around the inner sidewall to feel for any lumps and cuts. While doing this, also check for uneven wear, as this can indicate problems elsewhere on the car.

How do I check tyre pressure?

Keeping the tyre pressure at the manufacturer’s recommended level is an important way of reducing wear and tear on your car. It’s important to check when buying a car, too. 

Under-inflated tyres could mean that the steering might have been affected if the tyres had been like that for a long period of time.But a more serious consequence is that the tyres would overheat and increase the risk of failure. If they’re over-inflated, bear in mind the seller might have done this intentionally to compensate for leaking air or to disguise another fault.

To check the tyre pressure, you either need a pressure gauge, or an air pump with a built-in gauge. To find out the manufacturer’s recommended pressure, look in the manual or the door sill of most cars.

Check the spare tyre

These days it’s far from certain that there’ll be a full sized spare in the boot, let alone one that’s in good condition.  

Don’t assume that any new car you’re buying will have a full-sized spare in the boot.  Many cars now have a ‘skinny’ spare or just an emergency tyre sealant kit.

There may not actually be enough room to carry a full-size spare, but if there is then it may be possible to buy one as an optional extra.  You may also have to buy a modified boot floor and/or a jack and wheel removal tools too.

If there’s a sealant kit – check that the sealant hasn’t been used and not renewed.

See if the tyres match and how old they are

We do occasionally hear of stories where less reputable dealers have fitted a selection of odd, and old tyres to a car – they may all have legal tread but could be mismatched in terms of size, type or they’re just old.

Check the markings on tyre sidewalls to make sure that they’re the same size across axles.  It’s also worth checking that the tyres are all the same type – it’s not good practice to mix winter and summer tyres for example.

You can check the age of the tyres too – the last four digits following ‘DOT’ on the sidewall tell you the week and year in which the tyre was made. The first two numerals are the week (from 01 to 52) and the last two the year from 00 (2000) onwards.  Tyres made before 2000 only have three digits. 

There’s no law about tyre age but you should seriously consider renewing any tyre more than 10 years old, even if it appears to be in good condition.  Alarm bells should ring though if any tyre is older than the car itself as this would indicate that the car has been fitted with second-hand, part-worn tyres.

Need a general checkover for your car? Use the AA’s Vehicle Inspection service


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