27/10/2018
As a responsible driver in the UK, your car's annual MOT test is a crucial appointment, ensuring your vehicle remains roadworthy and safe for you and others. For any car over three years old, this assessment is mandatory, scrutinising key components from the exhaust system to the brakes. Among the most vital elements checked during this comprehensive inspection are your tyres. They are the only part of your vehicle that makes contact with the road, making their condition paramount for steering, braking, and overall stability. In 2023, the Driver and Vehicle Standards Agency (DVSA) reported that a significant 13% of all MOT failures were attributed to tyre-related issues, highlighting just how critical these unassuming circles of rubber truly are. So, understanding the specific requirements for your tyres to pass the MOT isn't just about avoiding a retest; it's about ensuring your own safety and adhering to legal legality on the road.
Can Under-Inflated Tyres Cause an MOT Fail?
Absolutely, yes. While often overlooked, correct tyre pressure is fundamental to your vehicle's performance and safety, and consequently, a critical factor in passing your MOT. An under-inflated tyre is not merely an inconvenience; it significantly impacts the tyre's contact patch with the road, leading to a range of detrimental effects. These include compromised handling, increased braking distances, excessive heat build-up within the tyre structure, and perhaps most dangerously, a heightened risk of a tyre blowout, especially at higher speeds. For these very compelling safety reasons, if your tyres appear visibly under-inflated during the MOT test, it will undoubtedly lead to a fail. The MOT tester is trained to spot such issues, as they indicate a direct threat to road safety. Therefore, it is imperative to regularly check and adjust your tyre pressures to the manufacturer's recommended levels, which can typically be found in your vehicle's handbook, on a sticker inside the driver's door jamb, or even inside the fuel filler flap.
Beyond Pressure: Comprehensive Tyre Checks for MOT Success
While correct tyre pressure is essential, the MOT test scrutinises several other critical aspects of your tyres. Neglecting any of these can result in a failure, potentially leaving you without a valid MOT certificate and facing the associated legal repercussions. Understanding each requirement will help you prepare your vehicle thoroughly.
Tread Depth: The Grip on Safety and Legality
One of the most commonly failed tyre categories in the MOT is insufficient tread depth. In the UK, the legal minimum requirement for tyre tread depth is 1.6mm. This strict measurement must be maintained across the central three-quarters of the tyre’s width, around the entire circumference. This 1.6mm threshold is not arbitrary; it's the minimum depth required to effectively disperse water and provide adequate grip in wet conditions. Tyres with less than this depth dramatically lose their ability to channel water, leading to aquaplaning and a severe loss of control.
If your tyre tread depth falls below this legal limit, it will result in an immediate MOT fail. Furthermore, the penalties for being caught by the police with illegal tread depth are severe: you could face three penalty points on your driving licence and a hefty fine of up to £2,500 per tyre. That's a potential £10,000 fine and 12 points for four illegal tyres, which could lead to a driving ban. To avoid this, you should check your tread depth regularly. Most tyres have built-in tread wear indicators – small raised bars within the main grooves. When the tyre tread wears down to the level of these bars, it’s time for a replacement. Alternatively, you can use a simple 20p coin: insert it into the main grooves of your tyre. If you can see the outer band of the 20p coin, your tyre tread is likely below the legal limit and needs replacing.
Matching Tyres on the Axle: Structural Harmony
For your vehicle's stability and predictable handling, tyres fitted across the same axle must have matching structures. This means if one tyre is radial, the other on the same axle must also be radial. Similarly, if one is a cross-ply tyre, its counterpart must also be cross-ply. Mixing these fundamental tyre constructions on the same axle will be a reason for an MOT fail. Radial and cross-ply tyres behave differently under various driving conditions, and having a mismatch can lead to unpredictable handling characteristics, particularly during cornering or emergency braking. It's crucial to note that this rule applies specifically to the tyre’s internal construction, not its tread pattern. While a mismatch in tread pattern across an axle will not cause an MOT failure, it is generally not recommended from a performance and handling perspective. For optimal vehicle dynamics and safety, it's always best to have identical tyres on the same axle, or even better, a matched set across all four wheels.
The Silent Guardian: Tyre Pressure Monitoring Systems (TPMS)
Modern vehicles are increasingly equipped with Tyre Pressure Monitoring Systems (TPMS). This advanced technology continuously monitors the air pressure in your tyres and alerts you via a dashboard warning light if one or more tyres are significantly under-inflated. If your car is fitted with a TPMS, then the functionality of this system will be thoroughly checked as part of the MOT. Should the TPMS warning light be illuminated on your dashboard, indicating a fault within the system or a persistent low-pressure issue that the system is reporting, this will result in an MOT fail. A non-functioning TPMS effectively removes a vital TPMS safety feature designed to warn you of potential tyre problems before they become critical. Regular servicing of your vehicle can help ensure your TPMS is in good working order and can assist in identifying any issues before they escalate into an MOT failure or, more importantly, a safety hazard.
Sidewall Integrity: More Than Just a Scratch
The sidewall of a tyre is its most vulnerable part, and any significant damage here can lead to an MOT failure. The sidewall bears the entire load of the vehicle and flexes constantly during driving. Damage such as a lump, bulge, or tear on the sidewall is a serious indicator of an internal structural problem. These often signify that the internal cords or plies, which provide the tyre with its strength and shape, have separated or broken. Such damage severely compromises the tyre's integrity and dramatically increases the risk of a sudden and catastrophic tyre failure, such as a blowout, especially at speed.
Even smaller cuts on a sidewall damage might only result in an advisory notice during the MOT test, particularly if they do not expose the internal cords. However, an advisory is a strong recommendation to address the issue promptly. It means the tester has identified a potential future problem. If you receive an advisory for sidewall cuts, it is highly advisable to replace the tyre sooner rather than later, as these minor cuts can quickly worsen with continued use, eventually leading to a full MOT fail or a dangerous tyre failure on the road.
Exposed Cords & Plies: A Clear Danger Sign
Beyond sidewall damage, any significant tear, cut, or abrasion on any part of the tyre that exposes its internal cords or plies is an immediate MOT failure. The cords (made of steel, polyester, or nylon) and plies are the foundational layers that give the tyre its strength and structural integrity. Once these are exposed, the tyre's structural integrity is severely compromised, making it highly susceptible to failure. This condition signifies that the tyre is no longer safe for use on the road and presents an extreme danger to the vehicle's occupants and other road users.
The Right Fit: Correct Tyre Type and Size for the Vehicle
While less common, fitting tyres that are the incorrect type or size for your specific vehicle can also lead to an MOT fail. Vehicles are designed to operate with tyres of a particular specification, including size, load rating, and speed rating. Using tyres outside of these recommendations can negatively impact handling, braking, and even the accuracy of your speedometer, making them unsafe and non-compliant with legal requirements.
Decoding the MOT Tyre Rules: A Quick Reference
To help clarify what constitutes a pass, an advisory, or a failure during your MOT tyre inspection, refer to the table below. It summarises the common tyre conditions and their implications.
| Tyre Condition | Pass | Advisory | MOT Fail |
|---|---|---|---|
| Tread Depth Above 1.6mm | Yes | No | No |
| Tread Depth Below 1.6mm | No | No | Yes (£2,500 fine per tyre + 3 points) |
| Small Sidewall Cuts (Not Exposing Ply) | Yes | Yes | No |
| Large Cuts, Bulges, Or Lumps | No | No | Yes |
| TPMS Light On (If Fitted) | No | No | Yes |
| Exposed Cords Or Ply | No | No | Yes |
| Incorrect Tyre Type/Size For The Vehicle | No | No | Yes |
| Incorrect Tyre Pressure (Visibly Under-Inflated) | No | Yes | Yes |
The Importance of Proactive Tyre Maintenance
As long as your tyres are in good working order and do not exhibit any of the issues discussed above, you should not encounter any problems with them during your MOT. However, passing the MOT is only one aspect of responsible car ownership. The true benefit of maintaining your tyres lies in enhanced safety, improved fuel efficiency, and extended tyre lifespan.
Regularly checking your tyres should become a routine part of your vehicle maintenance. This includes:
- Checking Tyre Pressure: At least once a month and before any long journey, use a reliable pressure gauge to ensure your tyres are inflated to the manufacturer’s recommended levels. Remember that tyre pressure should be checked when tyres are cold.
- Inspecting Tread Depth: Use the 20p test or look for wear indicators. Do this on all four tyres, and don't forget to check across the entire width of the tyre, as uneven wear can indicate other issues like poor wheel alignment.
- Visual Inspection for Damage: Routinely inspect the entire surface of your tyres, including the sidewalls and tread, for any cuts, bulges, cracks, embedded objects (like nails or screws), or signs of excessive wear.
- Checking for Uneven Wear: If you notice one side of your tyre is wearing faster than the other, or if there's significant wear in the centre or edges, it could point to problems with wheel alignment, suspension, or incorrect tyre pressure. Address these issues promptly with a professional.
Proactive tyre maintenance not only helps you sail through your MOT but also contributes significantly to your driving experience. Properly maintained tyres provide better grip, reduce the risk of accidents, improve fuel economy by reducing rolling resistance, and extend the life of your tyres, saving you money in the long run. It's an investment in your safety and your wallet.
MOT Tyres: Frequently Asked Questions
Here are some common questions drivers have regarding tyres and the MOT test:
Do I Need a Spare Tyre to Pass an MOT?
No, a spare tyre is not specifically checked during an MOT test, and you do not need to have one fitted to pass. However, if a spare tyre is fitted to the vehicle at the time of testing (e.g., if it's mounted on the back door of an SUV or under the vehicle), it must be road legal. This means it must meet all the same requirements as the other tyres on the vehicle regarding tread depth, condition, and suitable type.
How Old Can Tyres Be Before They Fail an MOT?
There is no specific age limit for car tyres that automatically results in an MOT failure. The MOT test focuses on the tyre's condition, tread depth, and structural integrity, regardless of its manufacturing date. However, tyres, especially older ones, can degrade over time due to exposure to UV light, heat, and general wear, even if they haven't covered many miles. Older tyres may show signs of cracking or hardening, which could lead to a failure if deemed unsafe. For HGVs, buses, and coaches, tyres older than 10 years are automatically illegal on the front axle and cannot be used on other axles if they show signs of distress.
Can a Car Fail an MOT for Under-Inflated Tyres?
Yes. As discussed, if tyres appear visibly under-inflated, this can cause an MOT failure. This is due to the significant potential safety risks associated with under-inflation, including reduced handling, increased braking distances, and the risk of a blowout. The tester will assess if the under-inflation is severe enough to compromise safety.
Can I Have Different Tyres on the Front and Rear Axles?
Yes, you can have different tyres on the front and rear axles, provided they meet the legal tread depth and load rating requirements for the vehicle. For example, you could have different brands or even different tread patterns front to rear. However, it is absolutely essential that tyres on the same axle are of the same construction (both radial or both cross-ply) to ensure consistent handling and safety.
Will My Car Fail If My Tyre Pressure Monitoring System (TPMS) Is Faulty?
Yes. If your car is equipped with a TPMS and the warning light is illuminated on your dashboard, indicating a system fault or a persistent low-pressure alert, this will result in an MOT failure. A functioning TPMS is considered a safety feature, and its malfunction means your vehicle is not providing essential safety information to the driver.
Do tyres have to match for MOT?
Tyres do not have to match in terms of brand or tread pattern across all four wheels, or even between the front and rear axles. However, as previously stated, you must always have tyres of matching construction (both radial or both cross-ply) on the same axle. If your tyres do not match in construction on a single axle, it will lead to an MOT failure. While not an MOT requirement, for optimal performance and handling, it is generally recommended to have the same tyres all around, or at least matching pairs on each axle.
Conclusion
In summary, your tyres are arguably the most crucial safety component of your vehicle, directly impacting its performance and your ability to control it. While under-inflated tyres can indeed cause an MOT failure due to the significant safety implications, they are just one piece of the puzzle. From maintaining adequate tread depth and ensuring structural consistency across axles to having a functional TPMS and free from critical damage, every aspect of your tyres is scrutinised during the MOT. By conducting regular, simple checks yourself and addressing any concerns promptly, you can ensure your vehicle not only passes its annual MOT with flying colours but, more importantly, remains safe and reliable on every journey.
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