How MOT Testers Assess Tyre Damage and Aging?

If a vehicle’s MOT due reminder pops up, one of the most important parts of this is checking the way the tyres are. Tyres are critical to road safety and can be significantly hazardous to drivers and other road users if damaged or excessively worn. Tyres are examined as part of the MOT test to check that they meet legal and safety standards.

This evaluation will consider tread depth, visible damage, and the condition of the structure of the tyre. Knowing how MOT testers judge tyre damage and how tyre ageing is regulated will help car owners do better preparing for the test and ensuring their car is roadworthy.

The MOT Testers’ assessment of tyre damage

The Driver and Vehicle Standards Agency (DVSA) provides MOT testers with a set of guidelines to follow when it comes to testing tyres. During this inspection, they look at the face of each tyre to ensure there is no irreversible damage, such as a bulge, cut, or embedded object. Internal structural damage to the tyre often caused by impact with potholes or kerbs, generally leads to bulges in the tyre sidewall.

These bulges are dangerous as they lower the strength of the tyre and the likelihood of a sudden failure. MOT regulations state that if you have a visible lump or bulge on the tyre’s surface, then the tyre will fail.

It also looks for cuts and embedded objects like nails or glass shards. They will test whether the tyre is safe to use by assessing the size and depth of the cut. Cuts over 25mm, or deep enough to expose the internal cords of the tyre, will also fail the MOT automatically, as stated in the DVSA guidelines. A replacement tyre must be fitted if the embedded object has damaged the tyre to the point of causing significant damage or puncturing the tyre's surface before the vehicle can pass the test.

Acceptable Size of Damage

Minor cuts and abrasions are allowed on tyres at the MOT test as long as they do not damage or detract from a tyre’s structure or safety. Acceptable small surface cuts do not expose internal cords and do not extend beyond 25mm in length.

But testers will reject any tyre with any kind of cut that is sufficiently deep to affect the structural integrity of the tyre. The same applies to embedded objects like small stones or glass fragments that have not perforated the tyre and caused air loss and will, in turn, not result in failure.

Another critical factor is sidewall damage. The sidewall of the tyre is the weakest part of the tyre and is prone to sudden failure anywhere where there is a bulge or tear on the sidewall. It will fail. Small sidewall cuts can be grounds for failure if they expose internal cords or if the sidewall is weakened.

Official Guidance and Cracks on Tyre Sidewalls                                                                                                   

The main issue is tyre cracks on the sidewalls, which are quite common with older tyres or vehicles not used that much. The natural ageing of the rubber may cause minor surface cracks to appear. According to the DVSA guidelines, sidewall cracks only fail if the internal structure or cords of the tyre are exposed, although putting them on the wrong side.

The sidewalls will be visually inspected for cracks, and the severity will be assessed. The vehicle can still pass the test if the cracks do not endanger the tyre's strength and are only superficial. However deep or wide spacing of cracks shows that the rubber is deteriorating and prone to failure under stress. Generally, tire manufacturers recommend replacing tires with 5 to 6 years of age regardless of the remaining tread depth to avoid age-related cracking and wear.

Official Guidance on Tyre Aging                                     

There’s no specific legal limit on the age of tyres on passenger cars, but the DVSA advises that you should remove tyres when they are visibly old. Tyres older than 10 years are automatically classed as unsafe for commercial vehicles such as minibuses and coaches on the front axle. It’s this guidance that emphasizes the importance of regular tyre checks, particularly for vehicles that are not put to frequent use or subjected to long periods of storage.

Although a tyre’s tread depth might appear sufficient, owners of vehicles need to check the sidewalls for cracks regularly. Symptoms of ageing include small cracks, rubber becoming hard, and the rubber turning a different colour. But correctly inflating tyres and storing cars in shaded, cool areas can prolong their lifespan.

Conclusion:

Being more aware of how MOT testers evaluate the quality of tyres can help vehicle owners avoid surprises and ensure their car continues to be on the road. Tyre maintenance includes regular tyre inspection, timely replacement of damaged tyres and paying attention to signs of tyre aging.

Top of the list when the MOT due reminder appears is checking tyres for bulges, cuts, embedded objects, and cracks. Drivers who want to pass the MOT test and protect themselves and their vehicle from the risk of breakdown can minimize the chances of failing while following official guidance and remaining proactive.