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TYPES OF TYRE - ANATOMYThe modern tyre is an intricately woven mixture of steel belts, advanced fabrics and

rubber compounds. A far cry from the solid piece of rubber of early days. Radial tyreshave become the industry standard, displaying many advantages over cross-ply tyres, in

terms of wear, heat resistance and rigidity.

Any car less than 20 years old, should be fitted with radial tyres. Never mix radial and

non-radial tyres. It could lead to poor handling and loss of vehicle control.

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TYPES OF TYRE - CATEGORIESStandard car tyres usually have a symmetrical pattern running across the entire tread.

Some high performance cars however are fitted with tyres with special tread patterns.

These asymmetric and directional tyres must be fitted the right way round on the wheel.

Incorrect fitting of both is a reason for MOT failure.

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ASYMMETRIC TYRES

Asymmetric tyres have differing tread patterns on the inner and outer edges of the tread

to improve performance.

On the outside edge, large stiff tread blocks help with cornering. On the inside edge,

smaller tread blocks are designed to shift water and improve wet grip. The middle of the

tread often has a continuous rib to help straight line stability.

The words inside and outside on the tyre sidewall indicate which way round the tyre

should be fitted.

DIRECTIONAL TYRES

Directional tyres are designed to rotate in one direction only which is indicated by an

arrow on the tyre sidewall.

These tyres are better at dispersing water which builds up in front of the tyre. They also

reduce road noise and improve directional stability.

WINTER TYRES

At temperatures below 7C, the rubber in normal tyres begins to harden, reducing gripon cold, wet roads, ice and snow.

In contrast, winter tyres stay soft and pliable at low temperatures. They retain grip, and

with the help of numerous special grooves in the tread called sipes, they provide

improved braking, handling and traction in all winter driving conditions. A typical summer

tyre may have around 200 sipes compared to a winter tyre with around 1500.

According to Tyresafe, a winter tyre can give up to 60% better grip in cold conditions and

can reduce braking distance by as much as six whole car lengths. That could make a

big difference in terms of road safety.

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Across Europe it is normal practice, even a legal requirement, for drivers to keep a set of

summer tyres and a set of specialist winter tyres. (see the TRAVELLING ABROAD

page)

In this country, winter tyres are not compulsory. In many parts of the country their use

could rarely be justified. In more remote areas, where winter really takes a grip, they

would make sense.

Whether to fit winter tyres is very much a personal decision depending on several

factors - risk of bad weather, driving ability and confidence on snow and ice.

Winter tyres are not suitable for all year round use. Summer tyres give better

performance when temperatures are higher and roads are dry, so you'll need two sets of

tyres.

Winter tyres must be fitted in sets of four. Fitting only one pair will affect the balance and

stability of the car.

ALL SEASON TYRES

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An alternative to winter tyres are All Season Tyres. These have a high silica content for

low temperature flexibility and a tread pattern somewhere between a normal summer

tyre and a winter tyre.

They are rarely as good as a specialist tyre but do perform better than a summer tyre onwintry roads and do avoid the hassle and cost of swapping wheels and tyres twice a

year.

PART WORN TYRES

When replacing tyres, the safest option is obviously to choose new tyres. Part worn

tyres can be fitted but various criteria have to be met. The Motor Vehicle Tyres (Safety)

Regulations 1994 set out minimum safety standards for the supply of part-worn tyres.

Under the Regulations, part-worn tyres (except retreads) should have an EC approval

mark and a speed and load capacity index moulded into the sidewall at the time of

manufacture. In addition, all types of part-worn tyres must be marked 'PART-WORN' in

upper case letters at least 4mm high.

It is illegal to have unsafe tyres in possession for sale.

TEMPORARY TYRES

Many vehicle manufacturers today supply their new cars with a non-standard spare

wheel and tyre. This is lighter and slimmer than normal to save weight and space. For

that reason, there is a maximum speed limit when using it - usually 50mph.

A space-saver wheel is intended for emergency purposes and should only be used as a

temporary measure. Motorists should be advised to get the original car tyre repaired or

replaced as soon as possible.