Tyre Failures: What Fails MOT?

The MOT test is a crucial annual inspection designed to ensure your vehicle is safe and roadworthy. While many drivers focus on brakes, lights, and emissions, tyres are a surprisingly common reason for a vehicle to fail its MOT. Understanding what constitutes a tyre failure is essential for any vehicle owner. This article will delve into the specific conditions and issues that will cause your tyres to be flagged during the MOT, drawing on real-world experiences to highlight the importance of proper tyre maintenance.

Tyre Tread Depth: The Legal Minimum

Perhaps the most well-known requirement for MOT tyre checks is the tread depth. In the UK, the legal minimum tread depth for car tyres is 1.6mm across the central three-quarters of the tyre's breadth. This minimum must be present in a continuous band around the tyre. During an MOT, the tester will use a tread depth gauge to measure this. If any part of the tyre falls below this limit, it's an automatic failure.

It's not just about the legal limit; significantly worn tyres, even if just above 1.6mm, can also affect braking distance and grip, particularly in wet conditions. The anecdote from CB about a tyre failure on a motorhome vividly illustrates the catastrophic consequences of using compromised tyres. While their failure wasn't directly due to tread depth (likely age and condition), it underscores the critical role tyres play in vehicle safety.

Tyre Damage: Cuts, Cracks, and Bulges

Beyond tread depth, the physical condition of the tyre is paramount. The MOT tester will meticulously inspect the tyre sidewalls and tread for any signs of damage. This includes:

• Cuts: Any cuts that are deep enough to expose the ply or cord beneath the rubber will result in a failure. A cut of 25mm or longer, or one that penetrates the fabric, is also a fail.
• Cracks: Ageing rubber can develop cracks. If these cracks are significant or deep enough to be visible within the main grooves of the tread or on the sidewall, the tyre will fail. This is often a consequence of tyres being exposed to sunlight and ozone over time, as highlighted by the potential age-related issues CB might have faced.
• Bulges and Lumps: These are extremely dangerous as they indicate structural weakness within the tyre. A bulge or lump on the sidewall or tread is an immediate fail. This often happens after a tyre has hit a pothole or curb with significant force.

Incorrect Tyre Type or Size

Your vehicle is designed to run on specific tyre sizes and types. Fitting tyres that are not the correct size or type for your vehicle can lead to an MOT failure. The tester will check if the tyres fitted match the manufacturer's recommendations, which are usually found in the vehicle's handbook, on a sticker inside the door frame, or on the fuel filler cap.

This includes issues such as:

• Mismatched Tyres: While not always a fail, having different types or brands of tyres on the same axle can be a reason for rejection, especially if they have significantly different performance characteristics. It's best practice to have matching tyres on the same axle, and ideally, all four tyres should be the same.
• Tyre Load and Speed Ratings: Tyres must be capable of supporting the vehicle's weight and its maximum speed. Tyres with insufficient load or speed ratings are a fail.

Reconstructed Tyres (Retreads)

While retreaded tyres are legal and can be a cost-effective option, they must meet specific standards. If a reconstructed tyre is fitted, it must be clearly marked as such and meet the relevant British Standard (BS AU 144). Tyres that are not properly marked or do not meet these standards will fail the MOT.

Tyre Contamination

It might seem unusual, but certain types of contamination can also lead to an MOT failure. If the tyre tread is contaminated with substances like oil or grease that are likely to cause damage or affect its grip, it can be rejected. This is less common but is checked during the inspection.

Tyre Pressure Monitoring System (TPMS)

For vehicles manufactured after 2012, a functioning TPMS is a component that can be checked during the MOT. If the TPMS warning light is illuminated on the dashboard, indicating a fault with the system, the vehicle will fail. This highlights that modern vehicles have more sophisticated systems that are also subject to inspection.

Summary of Common Tyre Failures:

Frequently Asked Questions (FAQs)

Q1: How often should I check my tyre tread depth?

It's recommended to check your tyre tread depth regularly, ideally once a month, and always before long journeys. This ensures you're aware of any potential issues before they become a serious problem or lead to an MOT failure.

Q2: Can I use part-worn tyres?

Yes, you can use part-worn tyres, but they must meet the same legal standards as new tyres, including a minimum tread depth of 1.6mm. They should also be free from damage like cuts, bulges, or exposed cords, and be properly marked. However, given the risks associated with older tyres, as highlighted by CB's experience, it's often advisable to opt for newer tyres if possible.

Q3: What happens if my tyres are worn but not quite at the 1.6mm limit?

While technically legal, tyres with tread depths close to the 1.6mm limit will offer significantly reduced grip, especially in wet weather. This can lead to a dangerous driving experience and may still be flagged by the MOT tester if they deem the condition to be a safety risk, even if not technically below the legal minimum.

Q4: Does the MOT test check tyre pressure?

No, the MOT test does not directly check tyre pressure. However, if your vehicle is equipped with a Tyre Pressure Monitoring System (TPMS) and the warning light is illuminated due to a fault, this will cause the vehicle to fail the MOT. It's important to maintain correct tyre pressures for safety and tyre longevity.

In conclusion, maintaining your tyres in good condition is not just about passing your MOT; it's about ensuring your safety and the safety of others on the road. Regularly inspecting your tyres for tread depth, damage, and correct fitment will help you avoid costly failures and potentially dangerous situations. The experience shared by CB serves as a stark reminder of what can happen when tyres are not up to standard. Don't let worn or damaged tyres compromise your journey; keep them in check!