Tyres are one of the most important components of your car. They are the ultimate control points for braking, steering and speed of your vehicle, yet only a very small percentage of the tyre's overall area is in contact with the road surface at any one time.

WATCH THE PRESSURE

Although cars are manufactured to give trouble free motoring over long distances, the tyres should still be checked weekly. Tyres expand when they heat up, and this happens when you start driving, so the best time to check your tyre pressures is first thing in the morning before you leave home. If you do check the pressures during a journey, and they read higher than the normal recommended pressure, do not reduce the pressure. It is less dangerous to drive with overinflated tyres than it is to do so with under inflated ones. However, the best solution is regular checking to establish the correct pressure at all times.

If the front tyres on a front wheel drive vehicle are overinflated, the tyre becomes hard, and the area of tyre in contact with the road is reduced. This then means that the grip of the tyre is also reduced. In bad weather, the steering becomes less positive, and the tyre will wear more in the centre, because of the overinflation. The same applies on the rear tyres of a rear wheel drive vehicle.

It is actually most dangerous to drive a car with underinflated tyres. The main reason for this is that underinflation causes the tyre to become less rigid, and consequently offers inferior control to the steering functions, and ironically can cause less of the tyre to be in contact with the road surface. It is equally dangerous to both front and rear tyres to have them underinflated. Continued use under these circumstances increases the likelihood of the tyre casing breaking, as the internal heat of the tyre will increase due to the lack of sufficient air inside the tyres. Furthermore, given the increasing environmental concerns facing us all, underinflated tyres lead to increased fuel consumption.

Every manufacturer's handbook recommends the size and type of tyre which should be fitted to that particular vehicle. The handbook will also contain information about the correct tyre pressures for driving under differing conditions - normal use, vehicle fully loaded/at speed and when towing.

Taking care of your steering and suspension system will also help to care for your tyres. Tyres that are not balanced properly can result in additional and unnecessary wear. One of the major causes of this wear is when one or more of the balance weights on the wheel rim has fallen off. The easiest way to tell if your tyres need balancing is when you feel a vibration in the steering wheel whilst you are driving.

DON'T MIX TYRES

Never put two different types of tyres on the same axle. Indeed, fitting a radial and a cross ply tyre on the same axle is illegal. It is possible to have radials on the rear and cross ply on the front axles, but not the other way round, and is not recommended. The only exception to this is in the case of temporary use spare tyres.

HINTS FOR SAFER TYRES

1. Make sure that your tyre pressures are correct.

2. Check your tyre tread depth. The legal minimum in the UK is 1.6mm. This tread depth must be maintained over threequarters of the total tread width of your tyre. It must also be maintained over the whole circumference of the tyre. Although these are the minimum levels, they do not necessarily mean that the grip of your tyre is automatically guaranteed over these levels.

3. Regularly check the inner and outer edges of your tyres for cuts and damage to the tyre walls.

4. Keep your car handbook available at all times, to make sure that you are maintaining the tyre operating pressures at the levels specified by the manufacturers for the conditions you are driving in.

5. If you are going on a long journey, check the spare tyre, as well as the main ones. Make sure that the tread depth is legal, and check your jack to make sure that is working properly.

WHAT DOES IT ALL MEAN

On the side of your tyre, you will see a code. This is an international code, which shows the type of tyre and the specification. Those numbers and letters tell you exactly about your tyre.
This is what they stand for (from left to right):

155 - is the nominal tyre width in millimetres.

70 - is the height as a percentage of width, the Profile. In this case (from rim flange to tread) it is 70% of 155mm, or 108mm.

R - means that it is a radial tyre.

13 - is the wheel diameter in inches.

75 - is the code for the carrying capacity per wheel of the car. Code 75 = 387kg.

T - is the maximum speed rating for the tyre. This tyre is rated at 118mph. The full table is below.

HOW FAST CAN MY TYRE GO?