Tyre Failures and Your MOT

The MOT test is a crucial annual check to ensure your vehicle is roadworthy and meets safety and environmental standards. While many components are scrutinised, tyres often play a significant role in whether your car passes or fails. A tyre failure can be a stressful experience, but understanding the reasons behind it and the consequences can help you prepare and avoid potential issues. This article will delve into what happens if your tyres fail an MOT test, explore common reasons for failure, and provide practical advice to keep your vehicle compliant and safe on the road.

Understanding the MOT Tyre Requirements

The Driver and Vehicle Standards Agency (DVSA) sets specific guidelines for tyre condition during an MOT test. These are designed to ensure your tyres provide adequate grip, stability, and braking performance. The primary areas of inspection include:

• Tread Depth: The legal minimum tread depth for car tyres in the UK is 1.6mm across the central three-quarters of the tyre's breadth. The tester will check this at several points around each tyre.
• Condition: Tyres must be free from cuts, cracks, bulges, or any other damage that could compromise their structural integrity. Exposed ply or cord is also a definite fail.
• Inflation: While not a direct failure point unless it causes visible deformation, tyres should be correctly inflated. Under or over-inflation can lead to uneven wear and affect handling.
• Advisory Notices: Even if your tyres don't fail outright, the tester might issue an advisory notice for issues like slight cracking, minor wear on the edges, or if the tread depth is approaching the legal limit. These are not failures but indicate potential future problems.
• Tyre Matching: Tyres on the same axle must be of the same type, size, and construction (e.g., both radial or both cross-ply). Re-grooved tyres are also prohibited on cars.

What Happens if Your Tyres Fail the MOT?

If your tyres fail to meet the MOT standards, your vehicle will receive a refusal of an MOT certificate. The failure will be recorded, and you'll be given a 'refusal of an MOT certificate' document detailing the reasons for the failure. Crucially, driving a vehicle that has failed its MOT, especially due to a dangerous defect like faulty tyres, is illegal. You can only drive the vehicle to a place of repair. If the failure is minor and deemed 'dangerous', you must not drive the vehicle at all until the defect is rectified. Driving a vehicle with dangerous defects could lead to points on your licence and fines.

Common Tyre Failures and Why They Happen

Several common issues can lead to tyre failure during an MOT. Understanding these can help you perform pre-MOT checks and address potential problems proactively.

1. Insufficient Tread Depth

This is perhaps the most frequent reason for tyre failure. Over time, the tread wears down with regular use. Factors contributing to rapid tread wear include:

• Under-inflation: Leads to wear on the outer edges of the tyre.
• Over-inflation: Causes wear in the centre of the tyre.
• Incorrect Wheel Alignment: Can cause uneven wear, often on one edge.
• Aggressive Driving: Frequent hard acceleration and braking wear down the tread faster.
• Driving on under-inflated tyres for extended periods.

The 1.6mm legal limit is a minimum. While tyres with this tread depth might pass, their grip, especially in wet conditions, is significantly reduced. It's generally recommended to replace tyres when the tread reaches around 3mm for optimal safety.

2. Damage to the Tyre Sidewall

The sidewall is the side section of the tyre between the tread and the rim. Damage here can be very serious:

• Cuts: A cut that penetrates the tyre's carcass is a failure. Even a shallow cut that exposes the reinforcing cords is a fail.
• Cracks: Ageing rubber can develop cracks. If these are deep or extensive, particularly if they affect the structural integrity, it's a fail.
• Bulges/Lumps: These indicate internal damage, often due to impact, where the internal structure of the tyre has been compromised. This is a critical safety defect and will always result in a fail.

3. Incorrect Tyre Type or Size

Manufacturers specify tyre sizes and types for a reason, relating to the vehicle's weight, speed rating, and handling characteristics. Fitting tyres that are:

• The wrong size for the vehicle.
• A different type on the same axle (e.g., a budget tyre on one side and a premium tyre on the other, or mixing radial and cross-ply tyres).
• Have an inappropriate speed or load rating for the vehicle.

These will lead to an MOT failure. It's essential to check your vehicle's manual or the sticker on the door frame for the correct tyre specifications.

4. Exposure of Casing or Ply

If the tread has worn down so severely that the underlying casing or reinforcing ply is visible, this is a definite fail. This indicates the tyre is significantly degraded and unsafe.

5. Re-grooved Tyres

While re-grooving is permitted for certain types of commercial tyres, it is illegal for car tyres unless the tyre was originally manufactured for re-grooving (indicated by 'Regroovable' on the sidewall). Using re-grooved car tyres will result in an MOT failure.

Preparing Your Tyres for the MOT

Proactive checks can save you the hassle and expense of a failed MOT due to tyre issues. Here's what you can do:

Regular Visual Inspections

Make it a habit to check your tyres at least once a month and before long journeys. Look for:

• Tread Depth: Use a tread depth gauge or a 20p coin. Insert the coin into the deepest part of the tread groove. If the outer band of the 20p coin is visible, the tread is likely below 3mm and nearing the legal limit.
• Sidewall Condition: Check for any cuts, bulges, cracks, or unusual wear patterns.
• Embedded Objects: Look for nails, screws, or stones stuck in the tread. While not always a fail, they can lead to punctures and should be removed carefully.

Maintain Correct Tyre Pressures

Check your tyre pressures regularly (when cold) and inflate them to the manufacturer's recommended levels. You can usually find this information in your car's manual, on a sticker inside the fuel filler cap, or on the driver's side doorjamb. Correct tyre pressure is vital for safety, fuel efficiency, and tyre longevity.

Wheel Alignment and Balancing

If you notice uneven tyre wear, it's a good idea to have your wheel alignment checked. Misalignment can cause tyres to wear out prematurely and affect your car's handling. Similarly, unbalanced wheels can cause vibrations and uneven wear.

What to Do After a Tyre Failure

If your tyres fail the MOT, you have a few options:

1. Get them repaired: Minor damage, like a puncture in the tread area that hasn't affected the sidewall or casing, might be repairable by a professional tyre fitter.
2. Replace the tyres: If the tread is too low, the damage is too severe, or the tyres are simply too old, you'll need to replace them. Ensure you replace them with tyres that meet the manufacturer's specifications for size, load, and speed rating. It's generally recommended to replace tyres in pairs (on the same axle) to ensure consistent handling.
3. Re-test: Once the faulty tyres have been repaired or replaced, your vehicle will need to undergo a partial or full re-test (depending on the garage's policy and the extent of the original failure) to confirm the issues have been resolved.

Table: Common Tyre MOT Failures vs. Advisories

Here's a quick comparison of issues that typically lead to a failure versus those that might result in an advisory notice:

Frequently Asked Questions (FAQs)

Q1: Can I drive my car if it fails the MOT due to tyres?

A1: You can drive your car to a pre-booked appointment at a garage for repairs. However, if the tyre defect is classified as 'dangerous', you must not drive the vehicle at all until it is repaired. Driving a vehicle with dangerous defects is illegal.

Q2: What if only one tyre fails the MOT?

A2: If only one tyre fails, you must replace or repair that specific tyre. However, it is strongly recommended to replace tyres in pairs (on the same axle) to ensure balanced handling and braking. If one tyre is significantly more worn than the other on the same axle, it's wise to replace both.

Q3: How much tread depth is acceptable?

A3: The legal minimum is 1.6mm across the central three-quarters of the tread. However, for optimal safety, especially in wet conditions, it's advisable to replace tyres when the tread depth reaches 3mm.

Q4: Can a bulged tyre be repaired?

A4: No, a bulged tyre indicates internal damage and is considered a dangerous defect. It cannot be safely repaired and must be replaced immediately.

Q5: What is the difference between an MOT failure and an advisory?

A5: An MOT failure means your vehicle does not meet the minimum legal safety standards and cannot be used on the road until the issues are rectified. An advisory notice highlights potential problems that are not serious enough to cause an immediate fail but should be monitored and addressed in the near future to prevent them from becoming failures.

Conclusion

Tyres are your vehicle's only point of contact with the road, making their condition paramount for safety. A tyre failure during an MOT test is inconvenient and can be costly, but it's a necessary check to ensure road safety for everyone. By understanding the MOT requirements for tyres, performing regular checks, maintaining correct tyre pressures, and addressing any signs of wear or damage promptly, you can significantly increase your chances of passing your MOT and, more importantly, ensure your vehicle remains safe and reliable on the road.

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