Tyred and emotional: why we should tread carefully

During the course of a week I spend my time engaged with professionals and very talented volunteers in the field of road safety.

It is easy to forget when surrounded by this peer group that for a lot of us, a car is just a car and the tyres are just at the corners to stop the wheel rims getting scratched on the road.

During a meeting I heard a bold statement: ‘some people don’t even know why we have tread on a tyre’ and that got me thinking.

I often hear the ‘a bald tyre has no grip.’ This tends to suggest that many people think the tread is there to give you grip, but if you have any interest in motorsport you will know that a racing car will use a slick tyre to get more grip. So does this mean the tread is there to give you less grip? Well let me try to get a grip and explain why we need tread and how a tyre works to keep you safe.

The tread, or grooves in the tyre, are there to allow the rubber to stay in contact with the road surface. Even when the road has a layer of water on the surface, the water is displaced into the grooves and it prevents the tyre being lifted off the road surface.

Modern tyres also have a series of very fine cuts in each tread block called ‘sipes,’ these assist in dispersing the water and allowing the tyre to touch the road.

As a tyre wears down the grooves become shallow and the sipes less efficient at dispersing water so it is likely grip will be lessened in adverse conditions.

The legal limit is 1.6mm of tread across the central ¾ of the tread and around its whole circumference, but remember this is an absolute minimum, in adverse conditions the more tread you have the safer you will be.  

Research at Motoring Industry Research Association (MIRA) shows a dramatic drop off in wet weather stopping distances below 3mm of tread depth. Most tyre manufacturers recommend changing at 3mm and the safety research backs them up.

Another consideration is if a tyre has worn out completely in one area, there may be a problem with your steering or suspension (that pothole you hit or the kerb you bounce up every morning to park). Get it checked, it may save your life.

If you have never checked your tyres now is a good time to start, look for damage any cuts or bulges may signify internal damage get them checked out, check the pressures, ideally when cold with an accurate gauge.

The recommended pressure can be found in the handbook, on a sticker in the door frame or in the fuel filler flap.

Failing that visit tyresafe.org which will give you access to a pressure checker and good safety advice.Remember 1mm on your tyre may make eight metres difference on the road, it is a no brainer really.

Richard Gladman, IAM RoadSmart’s head of driving and riding standards