Tyres and the Law

It is against the law to have:

• Car tyres with tread worn to below 1.6mm
• A mix of radial and cross ply tyres
• Over or under-inflated tyres
• Tyres with cuts, lumps, bulges or tears
• The wrong sort of tyre fitted to a vehicle or trailer

The UK law requires all vehicles are fitted with the correct type of tyre, in the correct size which is fit for the purpose the vehicle is being used. It is therefore, important you ensure you have the right tyres and that they are inflated to the manufacturer recommended level.

The legal limit for minimum depth of the tread on your tyres is 1.6 mm, across the central 75% of the tread around the complete circumference of the tyre.

For safety reasons it is recommended that you replace your tyres before the legal limit is reached. Many vehicle manufacturers recommend replacing at 3mm as more worn tread increases braking distances. For example, when the tread is 1.6mm it takes an extra car length (8 metres) to stop at 50 mph than if the tread was 3mm.

Legally, tyres of different construction types are not fitted to opposite sides of the same axle. The two main tyre types are radial and cross-ply, and these must not be mixed on the same axle. Mixing brands and patterns of the same construction type may be permissible depending on the vehicle type and manufacturers recommendation. Check your vehicle's handbook for tyre fitment details and options.

It is important to carry out a regular check to ensure your tyres are legal and safe. Remember, for each tyre which does not meet the legal requirements you face a £2,5000 fine and also up to 3 penalty points on your license. Also, your insurance is invalid if you have an accident when driving on illegal tyres.

Safety Standards

UK and European standards are in place to ensure tyres meet the same safety standards. All new tyres must meet European standards for load/speed performance, which is indicated by an 'E' or 'e' mark on the sidewall.

All retread tyres supplied in the UK must comply with the British Standard AU144e, and be marked with this number. This proves they have been thoroughly tested and meet the same performance standards as new tyres.

Second-hand tyres should only be purchased if they are marked 'part-worn' next to the E or BS mark, to show they have been properly checked for faults.

Tyre Technology

In recent years, tyre manufacturing has become an increasingly technical and proactive industry as manufacturers aim to go beyond traditional boundaries to improve their offering. Technological advances have played an important role in the development of the humble tyre. Here are some of the latest tyre technologies explained in plain English.

• Run Flat Tyres
• Eco Tyres and Silica
• Nitrogen

Run Flat Tyres

One of the major developments in tyres has been Run Flat Technology which enables vehicles to continue moving despite a loss in tyre pressure.

Two different approaches have been developed, the first being Reinforced Tyre Side Walls. The tyre is constructed from a new rubber compound which stops tyre destruction when a puncture occurs. This means that even when there is a complete loss of pressure, the tyre can still support the vehicle’s weight and handling remains unchanged. Manufacturers including Bridgestone, Continental, Dunlop, Goodyear and Pirelli.

The second approach, pioneered by Michelin, is the rubber clip which prevents the rim from cutting into the tyre when loss of pressure occurs.

All Run Flat technology must operate in tandem with tyre pressure monitors as these systems have such high levels of safety that sudden drops in pressure may go unnoticed. Pressure monitoring systems warn the driver of pressure changes via a warning indicator.

Eco Tyres and Silica

Eco tyres are known by many names including green tyres, environmentally friendly tyres, fuel saver tyres, low-rolling resistance. Regardless of the name they were developed to do the same thing: reduce fuel consumption without affecting performance or grip.

This is because of the addition of silica to tyres. Engineers are now able to produce tyre tread compounds which enable the tyre to absorb the differing amounts of energy required for fuel economy and grip – a task which was previously impossible with a single tyre.

Assuming that correct tyre pressures are maintained and making allowances for varying speeds and different driving characteristics, Eco-tyres offer a 20% reduction in rolling resistance which equates to a 5% fuel saving. In the promotion of the Michelin Energy tyre, Michelin claim this is a saving of £65 a year for the average motorist, a figure which covers the cost of the tyres over their lifetime.

The use of silica also offers substantial benefits in winter tyres and all-season tyres. Compounds using silica are more elastic and flexible at lower temperatures allowing better grip and braking during wintry weather. Vredestein claim to have improved wet skid performance by as much as 15%, substantially improving braking distances at the same time through the use of silica.

Nitrogen

Nitrogen has long been the accepted gas medium for filling aircraft tyres, racing tyres and heavy mining and construction vehicle tyres. Nitrogen is completely safe and, when mixed with oxygen to inflate car tyres, a constant pressure is maintained.

The rubber tyre is like a membrane, through which oxygen permeates three times faster than the nitrogen. The result is that the oxygen slowly leaks out through the rubber walls, and the under-inflation leads to higher tyre wear with a consequent decrease in safety and comfort, and higher fuel costs.

Having a tyre that does not deflate means you can enjoy improved fuel consumption and a higher level of safety. That’s not to say tyre pressure should not be checked regularly of course.