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How does tyre tread depth affect grip?

calendar Published on: Wednesday, 1st August 2018 | male icon Author: Kevin Thorpe

New tyres tend to have a tread depth of around 8mm, but as you clock up the miles behind the wheel, the rubber gradually wears down. Itís really important to be aware of the fact that if you let the tread depth get below 1.6mm, you risk being fined £2,500 and getting three penalty points on your licence per tyre.

Thereís a very good reason why the law prevents you from running your tread down too far - and thatís because of the essential role tyre tread plays in helping your car to grip the road

Here, we take a look at the impact of tread depth on stopping distances and aquaplaning to demonstrate why itís so important to check your tyres regularly and to replace them once they wear down beyond a certain point.

Significantly increased stopping distances

There have been a number of studies confirming a link between reduced tread depth and a deterioration of tyresí braking performance. One of the best known was commissioned by the British Rubber Manufacturers Association and conducted by engineering and testing consultancy MIRA.

Carried out on MIRAís test track in Nuneaton, the study looked at the performance of tyres with five different tread depths ranging from 6.7mm to 0.9mm. Vehicles were fitted with equipment to measure speed, distance and time, and were tested on both smooth concrete and hot rolled asphalt surfaces.

The research found that stopping distances increased significantly once tread depth dipped below 3mm. At 1.6mm (the legal minimum), the distance it took the vehicles to stop increased by 44.6 per cent on smooth concrete and 36.8 per cent on hot rolled asphalt compared with a tread depth of 6.7mm.

This clearly demonstrates that if you have tyres with a low tread depth, youíll take much longer to bring your car to a halt on the road. Whether you need to stop suddenly to avoid a collision with another vehicle, a pedestrian, an animal or something else, the consequences could be serious if youíre not able to do so in time.

RoSPA recommendations

Based on these findings, the Royal Society for the Prevention of Accidents (RoSPA) recommends that motorists change their tyres once their tread depth wears down to 3mm - which is 1.4mm above the legal minimum. Following this advice could help to make you safer on the roads. 

 RoSPA also highlights the importance of maintaining a suitable tyre pressure - noting that if a tyre is under or over inflated, less rubber comes into contact with the road surface. In turn, this leads to reduced grip and increased wear.

Higher risk of aquaplaning

If youíve ever experienced aquaplaning while driving in wet conditions, youíll know how dangerous and scary this can be. It happens when a layer of water builds up between your tyres and the road, causing a lack of traction and preventing you from braking, steering or accelerating. If youíre unable to restore proper contact with the road quickly, thereís a serious danger that youíll be involved in an accident.

Youíre at a much higher risk of aquaplaning if you allow your tyres to wear down too much. This is because the tread plays a vital role in dispersing water on the road surface. The grooving of the tread is designed to enable tyres to cut into surface water and make contact with the road beneath. So as your tyres wear down, their ability to resist aquaplaning declines. The more water there is on the roads, the quicker youíre likely to lose control of your car. 

As well as making sure your tyres have enough tread, there are other things you can do to lower the risk of aquaplaning. For example, itís important to ensure that your tyres are correctly inflated. Tyre specialists Michelin note that if pressures are 30 per cent or more below their recommended level, there is a sharp increase in the risk of aquaplaning. Lowering your speed will also help, particularly when youíre approaching areas of standing water.

Is it time for new tyres?

Given the safety benefits associated with having a decent tread depth, itís essential that you keep an eye on the level of wear of your tyres. It only takes a matter of moments to check them using a special depth gauge (which you can buy online or from most garages), and itís well worth making the effort. It will help to ensure you remain on the right side of the law, and it could play an important role in keeping you safe behind the wheel.

Obviously, if you discover that your tyres have a tread depth of below 1.6mm, youíll need to change them immediately. However, even if the depth is above the legal minimum, it might still be a good idea to replace them. In line with RoSPA guidance, itís advisable to change your tyres once they get to a tread depth of below 3mm.

How we can help

At TyrePlus, we offer an impressive range of great value tyres and should have exactly what you need when itís time to replace these essential pieces of kit. Simply choose the tyres you want, select a fitting location and let our experts do the rest. For added convenience, we also offer a mobile fitting service in case you canít make it to us. Just tell us which location works for you and weíll be there.

If youíd like further information on the importance of tyre tread or you have any questions about our services, donít hesitate to get in touch.


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