Tyre Technical Information and Law

Selection & fitment

When fitting replacement tyres ensure they are of the same size, load index and speed symbol as recommended by the vehicle manufacturer.

When tyres are not fitted in complete sets of four, we advise that tyre types are not mixed across the axle.

Consult Knights Tyre & Exhaust centre for fitment details for your car, especially if you are in any doubt.

Visual tyre care

By visually checking your tyres on a regular basis you can help maintain them in good condition throughout their service life and prevent having them changed unnecessarily or even failing prematurely. Check all tyres, including the spare, for these points;

1. Stones or nails

If not removed when embedded in the tread, stones and nails can work into the casing and cause damage. possibly leading to deflation.

2. Oil, fuel or paint

Oil, fuel or paint can have a harmful effect on the rubber compound used in tyres. Oil can make the tread rubber swell, reducing the pattern grooves and affecting adhesion. Immediate removal with detergent and plenty of water is recommended.

3. Damage and ageing

Damage in any form, e.g. cuts, bulges, vibration or air loss must be examined immediately by a tyre specialist. as they could be signs of potential tyre failure.

Ageing, such as surface cracking or crazing in the sidewall area of the tyre, should also be examined by a tyre specialist as soon as practical. Cracking and crazing occurs naturally through ozone damage and from over exposure of the tyre to the elements, especially sunshine. To reduce this effect, only wash tyre sidewalls when necessary and then just with water, or as little "car wash" as possible.

This advice applies equally to everyday vehicles as well as to little-used vehicles such as caravans or motorhomes.

4. Tyre service life

Regular inspection by a tyre specialist is recommended, and tyres that have been in use for five years or more should continue to be inspected by a specialist at least annually. Tyres which have been in service for ten years or more from the date of manufacture should be replaced.

For original equipment tyres, also refer to your vehicle manufacturer's recommendations.

5. Tyre tread wear

Tyre tread wear should be checked regularly. Abnormal wear is often an indication of a mechanical anomaly with the vehicle, such as incorrect alignment, or problems with the steering or suspension mechanism. Always have the mechanical parts of the vehicle checked and rectified by a professional. 

 Tread depth inspection

Are your tyres legal ? When should you change them ?

Always ensure your tyres conform to the UK minimum legal tread depth requirements of 1.6mm of tread left across the central three quarters of the tyre tread breadth and around the entire circumference of the tyre.

Various types of tread deapth indicator devices can be purchased from us or car product specialists. These can be dipped into the tread to measure the depth in millimetres. In addition most car tyres now have tread wear indicators set into the tread grooves,

Tyre positioning & handling

Knights Tyre & Exhaust Centres recommend that it is better to replace all four tyres at the same time, However due to the fact that most cars wear the tyres front and rear at different rates this is not always practical. If two tyres are being fitted to a vehicle then we advise that the new tyres should be fitted to the rear of the car and the part worn tyres fitted to the front.

Why fit the new tyres to the rear?

In extreme working conditions such as hard or emergency braking and cornering the stability of the vehicle is paramount. This is critical on wet or slippery roads. This also provides extra protection against sudden deflation in the rear tyres which is most likely to cause loss of control of the vehicle.

      Most modern cars are front wheel drive, the front tyres wear faster than the rear tyres.

The driver is therefore used to having less grip at the front as the tyres wear towards replacement.

By fitting new tyres to the rear and repositioning the tyres most worn to the front, the condition the driver is used to will have been retained after the tyre change.

4 Wheel drive vehicles

Knights Tyre & Exhaust Centres strongly recommend that tyres on 4x4 vehicles are used in identical sets of four (same size, make, pattern, load index/speed symbol ). The vehicle manufacturer's recommendations should also be followed.