The following are the main reasons that a tyre might need to be replaced, please see below for detailed descriptions:
- When tyres are worn down
- When tyres show signs of ageing
- If tyre is damaged
- If the tyre is abnormally worn
Modern tyres are very sturdy and can cope with most things. Punctures, though, can and do still happen. A tyre specialist should check your tyre after a puncture to decide whether it can be repaired.
Repairs to car tyres must only be carried out by a tyre specialist and in accordance with the current British Standards. Permanent repairs can only be carried out following removal of the tyre from the wheel to allow a thorough inspection internally as well as externally to ensure there is no hidden damage which could result in a catastrophic failure. To avoid such a hazard, neither externally applied plug repairs, nor liquid sealants may be considered as a permanent repair. Tyre manufacturers cannot be held responsible for problems resulting from their use.
Can you repair a run flat tyre?
The official response is that you need to check with the tyre manufacturer, their answer varies from a flat no, to placing the emphasis on the garage inspecting the tyre to make a call as to whether it is safe to repair or not. You will probably find that most national garages adopt the policy not to repair them, in contrast to independents that are likely to be more lenient. The difficulty is that unlike a standard tyre any damage caused by running on flat is not visible, although may still be present. There is certainly an argument that if the tyre warning light has just come on and you drive a short distance, slowly to a garage then a repair should be able to be carried out safely.
When your tyres are worn down
The legal minimum tread depth in the UK is 1.6mm throughout a continuous band comprising the central three-quarters of the breadth of tread and round the entire outer circumference of the tyre. However tyre wet grip deteriorates more rapidly in the second half of its tread life and wet stopping distances can dramatically lengthen. It is therefore advisable consideration is given to replacing tyres well before they reach the legal minimum.
All tyres have a tread wear indicator to display the 1.6mm depth that is required by law.
As mentioned previously tyre performance and stopping distances reduce dramatically when a tyre in the second half of its life, this is usually around 3mm and below. The simple 20p can be used to determine whether your tyre have reached this critical stage.
Also tyre safe produced the following useful video on the subject: http://www.youtube.com/watch?v=aVdsmaGckJQ
When tyres are showing signs of ageing
Tyres are designed and built to provide many thousands of miles of excellent service. For maximum benefit, tyres must be maintained properly to avoid tyre damage. There are many factors that will affect the life of the tyre such as temperature, maintenance, conditions of storage and use, load, speed, pressure as well as driving style. These will have a great impact on the length of service life you can expect from your tyres. Because of this it is important to inspect your tyres regularly for signs of aging that include cracking and tread deformation. It is also advisable that a tyre specialist inspects your tyres regularly after they are 5 years old to advise on when they should be taken out of service.
There is currently no agreement as to a specific age when a tyre should be removed regardless of appearance; tyre manufacturer’s recommendations vary from 5-10 years.
When was my tyre made?
All makes of tyre bear the so-called DOT code on the sidewall. This code provides information on the date of production. As of the year 2000 the code has four digits, the first two digits indicate the production week, the next two the year.
The example shown here is for the first week of the year 2000.
If the tyre is damaged
Tyres can be seriously damaged upon impact with solid objects on the road, kerbs, potholes or sharp objects. It is dangerous to ignore tyre damage; if swelling cuts or the carcass is visible then the tyre must be removed as soon as possible and inspected by an expert. In addition to this, if you have suffered from an impact but no visible damage is apparent it is still advisable for the tyre to be removed and inspected as internal damage may have occurred. Never use damaged tyres or tyres that have run flat or at very low pressures unless they have been thoroughly examined internally and externally by a tyre professional.
If the tyre is abnormally worn
Abnormal uneven tyre wear - in patches, in the centre, at the edges - may indicate a mechanical problem like improper wheel alignment, or a problem with, suspension or transmission. It could also be that you're driving with the wrong tyre pressure. If you notice abnormal wear, contact your tyre specialist.
To prevent uneven wear, have your wheels aligned by a tyre specialist. This will also extend tread life and give you a smoother ride.
Common causes of abnormal tyre wear
- Wear on one shoulder: suspension misalignment
- Wear on both shoulders: under-inflated tyre
- Wear along the tyre's centre: over inflation