Tyres and the Law

The law with regard to tyres fitted to vehicles for use on the public highway is lengthy.

However, the following will make you are of several major points of law:

It is illegal to have a car, light van or their respective trailers on the road if their tyres:

  • Have less than 1.6mm of tread remaining. (As detailed in ‘Watch Your Tread’)
  • They are not properly inflated, thereby making them unfit for use in which the vehicle is being put.
  • They are unsuitable for the use to which the vehicle or trailer is being put, or not compatible with the other types of tyres fitted.
  • They have a lump or bulge caused by the separation or partial failure of their structure.
  • Are of different construction (i.e. diagonal – cross-ply – or radial ply) are fitted on the same axle. Or, radial tyres are fitted on the front axle and diagonal (cross-ply) tyres on the rear axle.
  • Have any cords or piles exposed either through wear, cuts or abrasions.

Please note:

The full text of the law governing the use of tyres is contained in “The Road Vehicles (Construction and Use) Regulations 1986,” regulations 24 to 27 inclusive are concerned with tyres, including amendment No. 4, November, 1990.



Correct tyres pressures, as specified by the vehicle manufacturers, are essential to ensure the continued safety of the tyre fitted to your vehicle.
Tyre pressure must be checked at least once a fortnight when the tyres are cold and always before long or fully laden journeys, in accordance with the vehicle manufacturer’s handbook.

Under Inflation
Under inflation is a frequent cause of severe tyre damage, due to the excessive flexing of the tyre sidewalls. It also causes excessively rapid wear of the tread shoulder edges.

Over Inflation
Over inflation makes a tyre more prone to impact fracture and causing damage. It also causes increased wear of the central section of the tyre tread. Under-inflated, over-inflated, or unbalanced tyre pressure may seriously impair your vehicle’s steering and braking performance and its resultant safety on the road.


Watch your tread
Tyre treads are designed to give good wet road grip. The greater the depth of tread the greater the water clearing properties of the tyre, resulting in increased levels of grip.
The minimum tread depth for cars, light vans and their trailers is 1.6 mm in the grooves of the central three quarters of the tread pattern, and around the tyre’s total circumference.

Tread wear indicator
Most cars have tread wear indicators (TWI) set into the tyre tread. These become flush with the tyre surface when there is only approximately 1.6 mm of tread remaining.
Many tyres will have the letters TWI on the sidewalls as a guide to where the 1.6 mm indicators are located, as illustrated in the adjoining illustration.

Directional Tyres
Tyres with directional or asymmetric patterns should always be fitted so that they rotate in the correct direction as indicated by an arrow marked on the tyre sidewall.
Failure to observe this is classified as a reason for refusal to issue an NCT test certificate.
If a directional tyre has been fitted so that it rotates in the wrong direction (e.g. temporary use of a spare tyre following a puncture) then without undue delay the vehicle should be taken to a tyre dealer or garage so that a correct tyre can be fitted.
If only two directional/asymmetric tyres are fitted, they should be fitted to the rear axle of the vehicle only.

Rotating Tyre Positions
With modern vehicle suspension systems, especially when fitted with wider and/or lower profile radial-ply tyres, it is not recommended to rotate or reposition the tyres on the vehicle.
All tyres develop particular and different types of wear on whichever corner of the vehicle they are fitted.
Rotating or repositioning tyres will initially change the handling characteristics of the vehicle as well as well as temporarily increasing the overall rate of tyre wear.

Tyre Valves
When ‘Snap-In’ valves are used with tubeless tyres, new valves should be fitted when either a new tyre or repaired tyre is fitted. Always ensure airtight valve caps are fitted. Because of centrifugal and other forces, clamp in valves are preferable for very high-speed operations.

Inner Tubes
A tyre not marked tubeless must be fitted with a tube. A new tube of the correct size should always be fitted when any new tube tyres are fitted. In the event of a puncture, the fitting in an inner tube is not a substitute for a proper vulcanised repair.

Tread Wear
A number of factors can account for marked differences in tyre wear on similar vehicles.

  • High speeds especially when cornering, fierce or hard breaking can cause rapid tread wear and you are the only person who can control it.
  • Mechanical irregularities such as, incorrect camber angles, out of balance wheels, worn dampers or wheel bearings, grabbing or unbalanced brakes and under or over inflation all cause rapid tyre wear. Wheel misalignment/tracking can also be the cause of exceptionally rapid tyre wear.
  • Each time you check your tyre pressures, we suggest you look closely at the tyre treads. If you notice that there appears to be uneven wear (as indicated here), we recommend you seek professional advice, it could end up saving you money at least!

Accidental Damage
Tyres are of robust construction but will give their best only if fairly used and treated.

DON’T, if at all possible, drive, even at low speeds, up kerbs, over large surface irregularities or through pot holes, as the sudden and extreme severe shock loading can result in weakening or fracturing of the tyre casing, which may result in its rapid or total failure.

The resilient sidewall rubber and treads of modern tyres may not immediately show any evidence of damage after hitting such irregularities, so we therefore recommend, for your own safety, if such damage is suspected, that the tyre should be thoroughly inspected by an expert, including removing it from the wheel.

Further to the above we recommend you regularly inspect your tyres, in order to check for any splits or bulges in the sidewalls (AND don’t forget the inner sidewall), plus at the same time remove any flints, nails or other objects embedded in the tread rubber.

Long nails may cause secondary internal damage in the casing. Should a long nail be removed from the tyre, it is most important that the tyre is removed from the wheel and a full internal inspection is carried out by a tyre expert.

Age Deterioration
Tyres deteriorate with age. This can show as cracking of the tread and sidewall rubber. Tyres fitted to vehicles, which are parked for long periods of time exposed to sunlight, particularly in costal regions, or those used infrequently on short slow journeys, will tend to age and crack quicker than those, which are used and run frequently at higher road speeds over greater distances.

If you notice cracking or splitting of the tyres on your vehicle, as illustrated in the accompanying photographs, for your own safety, make sure an expert checks them.


The mechanics of long tyre life:

  • Maintain correct inflation pressure
  • Avoid harsh braking, rapid acceleration and fast cornering, all of which increase the rate of tread wear.
  • Do not overload your vehicle (check with the vehicle handbook)
  • Avoid driving over kerbs and hitting potholes and other severe road irregularities. Do not scrape tyres along the kerb.
  • Maintain tyre and wheel assemblies in correct balance.
  • Check periodically for wheel misalignment and other mechanical irregularities.

Ensure your vehicle suspension, steering and braking components are regularly maintained; they all contribute to satisfactory and safe tyre pressure.