The MOT test is a critical annual examination for vehicles in the UK, ensuring they meet road safety and environmental standards. Among the various components assessed, tyres are a significant factor in many MOT failures. With tyre-related failures reaching a record 2.15 million vehicles in 2023-24, understanding the specific requirements and potential issues can help motorists avoid unnecessary complications and ensure road safety.
Understanding tyre bulges and their dangers
What Is a Sidewall Hernia and How to Identify It
A tyre bulge, commonly referred to as a sidewall hernia, manifests as a noticeable weakness in the tyre's sidewall, resulting in a visible bubble or swelling. These abnormalities typically develop after impact damage, such as hitting kerbs or driving through potholes with significant force. When examining your tyres, run your hand along the sidewall and look for any unusual protrusions or deformities. Unlike regular wear patterns that develop gradually, tyre bulges often appear suddenly following an impact and represent a serious structural compromise.
Why tyre bulges pose serious safety risks
Tyre bulges indicate internal damage to the tyre's fundamental structure and represent a critical safety concern. The compromised area creates a weak point that dramatically increases the risk of catastrophic tyre failure, particularly at higher speeds or when carrying heavier loads. The danger lies in the unpredictable nature of when the tyre might fail completely, potentially resulting in a sudden blowout that could cause the driver to lose control of the vehicle. This scenario becomes especially hazardous on motorways or during adverse weather conditions when vehicle stability is already challenged.
Mot regulations regarding tyre defects
Legal framework: the road traffic act and mot standards
The MOT testing guidelines, underpinned by the Road Traffic Act, explicitly classify tyres with bulges as unroadworthy and illegal for use on public roads. Since the MOT changes implemented in May 2018, the assessment criteria have become more stringent, with tyre defects categorised as minor, major, or dangerous. A tyre bulge is invariably classified as a major defect, resulting in an immediate MOT failure. This classification reflects the serious nature of the issue and the potential risk it poses to road users. The legal framework also stipulates that driving with such defects can result in severe penalties, including fines of up to £2,500 per defective tyre and potential licence points.
Common tyre issues leading to mot failures
Beyond bulges, several other tyre conditions can trigger an MOT failure. Insufficient tread depth below the legal minimum of 1.6mm across three-quarters of the tread width is a common issue. The MOT test also scrutinises tyres for cuts or tears that might expose internal cords, improper tyre fitment including mismatched structures across the same axle, and under-inflation. Vehicles equipped with Tyre Pressure Monitoring Systems (TPMS) must have these functioning correctly, as malfunctions will result in failure. The inspection also verifies that tyres meet the correct size, speed, and load ratings specified for the vehicle. These comprehensive checks aim to ensure that all aspects of tyre safety meet the required standards before a vehicle can be deemed roadworthy.
Managing and preventing tyre damage
Essential tyre maintenance practices
Regular tyre maintenance forms the cornerstone of preventing MOT failures and ensuring optimal road safety. Motorists should develop the habit of checking tyre pressure at least monthly, adjusting according to the manufacturer's specifications found in the vehicle handbook. Visual inspections should include looking for signs of unusual wear patterns, which might indicate alignment or suspension issues. Monitoring tread depth using the 20p coin test provides a quick assessment; if the outer band of the coin remains visible when inserted in the tread, the depth may be approaching the legal minimum. Avoiding aggressive driving behaviours such as harsh acceleration, emergency braking, and taking corners at excessive speed significantly reduces uneven wear and structural stress on tyres.
Responding to a Failed MOT Due to Tyre Bulges
If your vehicle fails its MOT due to a tyre bulge or other serious tyre defect, immediate action is essential. Unlike advisory notices that might be issued for minor defects, a major defect like a tyre bulge means the vehicle is not legally roadworthy. The appropriate response is prompt replacement of the affected tyre, ideally at the testing centre or via a mobile tyre fitting service. Attempting to drive with a known tyre bulge not only risks a catastrophic failure but also constitutes a legal offence that could result in substantial fines and penalty points. After replacement, request a partial MOT retest, which may be offered at a reduced fee if completed within a specified timeframe at the same testing station.
Staying informed about your tyres
Decoding tyre markings and their significance
Understanding the information encoded on your tyres empowers informed maintenance decisions. The sidewall markings include crucial details such as tyre dimensions, load index, and speed rating. For instance, a marking like '205/55 R16 91V' indicates a width of 205mm, an aspect ratio of 55%, radial construction, a 16-inch rim diameter, a load index of 91 (supporting up to 615kg), and a speed rating of V (capable of speeds up to 149mph). Additionally, a four-digit code reveals the manufacturing date, with the first two digits representing the week and the last two indicating the year. This information helps ensure replacement tyres match the vehicle's requirements and allows monitoring of tyre age, especially important for certain commercial vehicles where age limits apply.
Seasonal Considerations for Tyre Care and Safety
Seasonal changes significantly impact tyre performance and maintenance needs. During colder months, tyre pressure naturally decreases as air contracts with dropping temperatures, potentially leading to under-inflation and increased fuel consumption. Conversely, summer heat can cause pressure to rise, risking over-inflation and uneven wear. Regular pressure checks become even more crucial during these transitional periods. Winter conditions demand particular attention to tread depth for adequate grip on wet or icy surfaces, with some experts recommending depths greater than the legal minimum. Being mindful of how different road conditions affect tyre wear and performance throughout the year contributes to extended tyre life and enhanced safety regardless of the season.
Legal Consequences of Driving with Defective Tyres
Driving with defective tyres in the UK is not only dangerous but also illegal, carrying serious legal ramifications. A tyre bulge, also known as a sidewall hernia, represents a critical weakness in the tyre's structure that substantially increases the risk of a catastrophic blowout, particularly at motorway speeds. The Road Traffic Act explicitly classifies vehicles with bulging tyres as unroadworthy, making their use on public roads unlawful.
Penalties for Non-Compliance with Tyre Safety Standards
The penalties for failing to maintain proper tyre standards are quite severe in the British legal system. If caught driving with defective tyres, motorists face a maximum fine of £2,500 per faulty tyre. For commercial vehicles, these fines can reach up to £5,000 per tyre. Beyond financial penalties, drivers also risk receiving penalty points on their licence. The gravity of these sanctions reflects the paramount importance placed on tyre safety within UK road safety regulations. MOT statistics reveal a concerning trend, with a record 2.15 million vehicles failing their MOT tests due to tyre defects in 2023-24—an increase from previous years. What's particularly worrying is that 36% of these failures (over 750,000 vehicles) had prior tyre-related advisories that weren't addressed, suggesting many motorists are neglecting essential tyre maintenance despite warnings.
The appeals process for tyre-related mot failures
Should your vehicle fail its MOT due to tyre issues, you have legal options available. Whilst a tyre bulge will always result in an automatic MOT failure as a major defect, you might question other tyre-related failures. The appeals process begins by discussing concerns directly with the testing station. If this proves unsatisfactory, you may seek a second opinion from another MOT testing facility. For formal appeals, you must complete the VT17 form within 14 days of the test, submitting it to the Driver and Vehicle Standards Agency (DVSA). Be aware that during this process, the vehicle remains officially unroadworthy if failed for tyre defects and shouldn't be driven except to repair facilities or to another MOT test. MOT regulations stipulate specific tyre requirements: tread depth must be at least 1.6mm across three-quarters of the width, tyres on the same axle must match in structure, sidewalls must be free from significant damage, and there must be no exposed cords or plys. Tyres must also be properly inflated, and any Tyre Pressure Monitoring System must function correctly.