Why is tread depth so important?

The humble car tyre. Most start life with approximately 8mm of tyre tread when first fitted to your car, tread that your car needs to help you grip the road and remain in control of the vehicle. But from the moment a new tyre is fitted, it will slowly begin to lose that tread with every mile travelled. And while sensible drivers who avoid sharp braking and cornering at speed can preserve their tyres for longer, even the most careful driver cannot avoid one inevitable fact, the more miles you drive, the more your tyre tread will wear down until eventually, when it reaches a minimum depth of 1.6mm, you’ll need to replace that tyre. Such is the life of a car tyre, or should that be ‘the circle of life’? Sorry.

But if you’re putting off that tyre change because you can’t find the time or perhaps are downplaying the severity of a bald tyre, here are 3 reasons why tread depth is so important.

1. Improved stopping distances

This is an obvious one but in the event of an emergency braking manoeuvre, your car relies on your tyre tread to grip the road and come to a stop in the shortest possible distance. Braking distance can be directly correlated to tyre tread depth so as your tread wears out, grip decreases and braking distance increases. For this reason it is recommended that tyres are replaced when the tread depth reaches 3mm in order to maintain optimum braking performance. For more information on the link between tyre tread and braking distance, see our previous blog entry - Tread carefully – braking distance increases as tread wears out. To make matters worse, your stopping distance will increase still further when driving in wet conditions. Which brings us neatly onto…

2. Improved aquaplaning resistance

Tyres have to work much harder when driving on wet surfaces in order to prevent aquaplaning. Aquaplaning occurs when the water between your tyres and the road surface cannot be displaced quickly enough resulting in the driver losing control of the vehicle. If your car begins to aquaplane, you won’t be able to steer or brake until your tyres regain contact with the road. It’s a scary experience but one that can be avoided by checking your tread depth. Tyre tread doesn’t just help to grip the road, the tread pattern is designed in such a way to remove water from the road surface as you drive. Typically a tyre with adequate tread can displace enough water to fill a bucket every 7 seconds – that’s a lot of water. But as your tyre tread becomes worn so too does its ability to evacuate that water from the road which greatly increases the chances of aquaplaning.

3. Illegal tyres could mean costly fines and risk of conviction

Driving with tyres under the legal tread limit isn’t just a safety risk, it’s against the law. The legal minimum tread depth in the UK is 1.6mm across the central three quarters of the breadth of the tyre and around the full circumference. If you are pulled over by the police and your tyre tread is below the legal limit you could be fined up to £2,500 and be landed with 3 penalty points on your licence. What’s more if you are convicted of using a vehicle with defective tyres, your insurance premium could go up by as much as 69% according to Confused.com. Last year the Ministry of Justice released figures that showed that in 2012, more than 10,000 drivers in England & Wales ended up in court due to defective tyres. Can you really afford to take the risk?

How to check your tyre tread

By now you might be wondering how best to check your tyre tread to ensure you don’t fall foul of the above issues which could prove costly both to your wallet and, more seriously, the health and safety of yourself and other road users. Tyre tread gauges can be purchased which can tell you precisely how much tread you have remaining. However, a simple way to check to see if your tyre tread depth exceeds the minimum legal limit is to use the 20p method. Simply find a 20p piece and place it inside the main tread grooves of the tyre and make sure your eyeline is level with the tyre. If the outer band of the 20p piece is obscured by the tyre then your tyres have adequate tread. Make sure you do the 20p test in at least 3 different locations across the tyre as you may have uneven tyre wear. If you can see the outer band of the 20p piece on any of the tests, your tyres could be approaching the legal limit so it’s advised to have them checked as soon as possible.

Check your tyre tread at least once a month to ensure your tyres stay road-legal and if you are in any doubt or have concerns about your tyre tread, pop into your nearest Kwik Fit and we’ll check your tyres for free. Find my nearest Kwik Fit centre.