Tyres Fail MOT: The Most Common Causes
A significant number of vehicles fail their Ministry of Transport (MOT) test each year due to issues with their tyres. Understanding precisely why tyres fail MOT inspections is crucial for any car owner. The primary reasons typically revolve around the tyre's condition, tread depth, and structural integrity, all of which are checked rigorously by authorised testers to ensure road safety.
- Tyres failing MOT tests are often due to insufficient tread depth.
- Cracks, bulges, or cuts affecting the tyre structure are common failure points.
- Tyres must be the correct size and type for the vehicle.
- Adverse modifications or mismatched tyres can lead to failure.
The MOT test is designed to ensure vehicles meet minimum safety and environmental standards. Tyres are a critical safety component, directly impacting grip, braking, and steering. When a tyre exhibits wear beyond legal limits, shows signs of damage that compromises its strength, or is otherwise unsuitable for the vehicle, it will result in a failure. Paying attention to these aspects before your test can save you time, money, and the inconvenience of a retest.
It’s not just about the tread. The side walls are just as important. A tyre might have plenty of tread left, but if its sidewall is damaged, it’s a fail. This damage can come from accidental impacts, such as hitting a kerb, or from general wear and tear that causes the rubber to degrade over time.
This is why regular visual inspections are so important.
Tread Depth: The Legal Minimum
The most frequent cause for tyres failing an MOT is having tread that is below the legal minimum depth. In the UK, this limit is set at 1.6 millimetres across the central three-quarters of the tyre's width, measured in a continuous band. However, testers often look for more than just meeting the bare minimum. Significantly worn tyres, even if just above 1.6mm, might be noted as advisories and can still impact the vehicle's safety, especially in wet conditions. Using a tread depth gauge or even a 20p coin can give you a good indication before your MOT; if the outer band of the coin is visible when inserted into the deepest part of a tread groove, the tread is likely below the legal requirement.
Structural Damage: Cuts, Cracks, and Bulges
Beyond tread wear, the physical condition of the tyre is heavily scrutinised. Any cut, abrasion, or tear that is visible on the tyre's surface or sidewall, and is long enough (over 25mm) or deep enough to reach the tyre casing, will cause an MOT failure. Similarly, signs of internal damage, such as bulges or lumps on the sidewall, indicate that the tyre's structure has been compromised. These often arise from impacts and mean the tyre is at risk of bursting and must be replaced immediately. Even minor cracks that appear in the rubber, especially on older tyres, can be deemed a failure if they are significant enough to suggest degradation or potential failure.
Common Tyre Issues Beyond Tread Depth
What else can lead to a tyre failure during an MOT? While tread depth is a primary concern, MOT rules also cover several other critical aspects of tyre condition and suitability for the vehicle. Ignoring these can result in an unexpected fail, even if your tread is perfectly adequate. Understanding these nuances ensures a comprehensive approach to tyre maintenance.
Incorrect Tyre Size or Type
All tyres fitted to a vehicle must be the correct size and type as specified by the vehicle manufacturer. This information is usually found in the vehicle's handbook, on a sticker inside the driver's door frame, or sometimes on the fuel filler flap. Using tyres that are too small, too large, or of an inappropriate load or speed rating can affect the vehicle's handling, braking performance, and stability, leading to an MOT failure. If you've recently had tyres fitted or changed, double-check that they match the manufacturer's recommendations.
Mismatched Tyres and Other Anomalies
A car typically has two tyres on the front axle and two on the rear. For safety and optimal performance, tyres on the same axle must be a matching pair, meaning they should be the same size, type, brand, and tread pattern. While it is not a failure to have different tyres on the front compared to the rear, fitting non-matching tyres on the same axle is a definite MOT fail. Testers will also check for any foreign objects embedded in the tyre that could cause damage or pose a hazard, and ensure that tyre valves are in good condition and not leaking.
Ensure your tyres are fitted correctly.
The MOT test enforces strict standards for tyre safety to protect all road users.
Run-Flat Tyres and Temporary Spares
While run-flat tyres are permitted, if a vehicle is fitted with them, they must be in a serviceable condition. If a run-flat tyre shows signs of damage or is below the legal tread depth, it will fail. Similarly, if a vehicle is equipped with a temporary spare tyre as its standard fitment (some smaller city cars do this), that spare tyre must also meet the same MOT standards as a regular tyre, including tread depth and condition. If a temporary spare is fitted only for use after a puncture, it usually isn't checked unless it's the only tyre on that axle or is otherwise obviously defective.
Proactive Checks: Keeping Your Tyres MOT-Ready
Preventing an MOT failure related to tyres is far more straightforward than dealing with the consequences of a fail. By adopting a proactive approach to tyre maintenance, you can significantly increase the likelihood of your vehicle passing its annual inspection and, more importantly, ensure your car remains safe to drive.
Check your tyre pressures monthly and adjust them according to the vehicle manufacturer’s recommendations, usually found on a sticker inside the driver's door frame.
Regular Visual Inspections
Make it a habit to visually inspect your tyres at least once a month, or before any long journey. Look for any signs of wear and tear, such as uneven wear patterns, cuts, bulges, or embedded objects. Pay close attention to the sidewalls as well as the tread. If you notice anything concerning, it’s best to get it checked by a professional tyre specialist sooner rather than later. This simple habit can identify potential issues before they become serious safety hazards or MOT failures.
Understanding Tyre Age and Condition
Tyres degrade over time, even if they aren't used extensively or driven on rough surfaces. The rubber compounds can harden and crack, especially if exposed to prolonged sunlight or extreme temperatures. While there is no specific MOT rule about tyre age, tyres that are visibly old and show signs of perishing or cracking will likely fail. The manufacturing date is usually indicated by a four-digit code on the tyre's sidewall (e.g., '2519' means the tyre was manufactured in the 25th week of 2019). If your tyres are more than six years old, consider having them professionally assessed, regardless of tread depth.
Don't let age be a hidden MOT killer.
When to Seek Professional Advice
If you are ever in doubt about the condition of your tyres, or if you suspect they might be nearing the end of their life, consult a qualified tyre professional. They have the expertise and equipment to assess your tyres thoroughly and advise on whether replacement is necessary. They can also check your wheel alignment, which, if faulty, can cause uneven tyre wear and potentially lead to premature failure. Addressing these issues proactively ensures your vehicle is not only compliant with MOT regulations but also safe and efficient on the road.