09/02/2007
The Ministry of Transport (MOT) test is a vital annual check designed to ensure your vehicle is safe and roadworthy. While many drivers focus on the engine or brakes, the wheels and tyres are equally critical components that undergo rigorous inspection. Understanding what the testers are looking for can help you prepare your vehicle and avoid unexpected failures. This comprehensive guide will break down the MOT requirements for road wheels and tyres, covering everything from wheel security to tread depth and tyre age.
5.2.1. Road Wheel and Hub: Ensuring Secure Fitment
The first area of inspection for wheels focuses on their secure attachment to the vehicle. This is paramount for safety, as a loose wheel can have catastrophic consequences. The MOT tester will meticulously examine the wheel nuts, bolts, and studs.
Key Defect Categories for Wheel Security:
| Defect Description | Severity |
|---|---|
| A wheel with one or more loose or missing wheel nuts, bolts, or studs. | Major / Dangerous |
| A spigot-mounted wheel hub that is excessively worn or damaged to the extent that wheel security is adversely affected. | Major / Dangerous |
It's essential to ensure all wheel fasteners are present and correctly tightened. While a single loose fastener is a failure, multiple missing or loose ones are considered a dangerous defect, highlighting the extreme importance of this check.
5.2.2. Road Wheel Condition: More Than Just Aesthetics
Beyond security, the physical condition of the road wheels themselves is assessed. This includes checking for structural integrity and proper seating.
Important Considerations for Wheel Condition:
- Only wheels fitted to the vehicle at the time of inspection are checked. While spare wheels aren't tested, any defects should be reported to the owner.
- Wheel hub caps must not be removed for inspection.
- Detachable spring retaining rings on semi-drop centre wheel rims are acceptable if they are securely fitted.
Defect Categories for Road Wheel Condition:
| Defect Description | Severity |
|---|---|
| Any fracture or welding defect on a wheel. | Dangerous |
| A tyre retaining ring that is not correctly fitted or is likely to come off. | Major / Dangerous |
| A wheel that is badly distorted or worn between the wheel and hub at the spigot mounting, or distorted/worn to the extent the wheel or tyre could detach. | Major / Dangerous |
| A wheel and its fixings not being compatible. | Major |
Cracks, significant distortion, or incompatible wheel and hub designs can all lead to an MOT failure. These issues compromise the wheel's structural integrity and can lead to accidents.
5.2.3. Tyres: The Rubber Meets the Road
Tyres are a cornerstone of vehicle safety, directly impacting grip, braking, and handling. The MOT test scrutinises several aspects of your tyres.
Tyre Size and Markings
Tyre size markings, such as 215/55R15, indicate crucial dimensions like width and aspect ratio. Standard car tyres typically have an aspect ratio of 82% or 80%, and these can be mixed. Dual markings on tyres are also acceptable. When it comes to load rating and speed rating (primarily for Classes 5 and 7 vehicles), ensure they are suitable for the vehicle's axle weight and intended use. If no speed rating is shown, it's assumed the minimum requirements are met.
Tyre Structure Compatibility
A key rule is that tyres of different structures, such as radial-ply and cross-ply, must not be mixed on the same axle. Steel and fabric radial-ply tyres are considered the same structure. While mixing run-flat and conventional tyres is permitted, it's not recommended for optimal performance.
Tyre Condition and Fitment
Minor tyre flexing or contact with vehicle parts due to suspension movement is not a failure. However, if a tyre is fouling a vehicle part at the time of the test, it will result in a failure. This also applies to contact with lock stops if they are improperly maintained and damage the tyres. When assessing cuts:
- Any ply or cord visible without touching the tyre is a fail.
- If, by opening a cut with a blunt instrument, exposed ply or cord can be seen (regardless of size), it's a fail.
- Cuts where cords can be felt but not seen (after opening with a blunt instrument) exceeding 25mm or 10% of the section width (whichever is greater) are also a fail.
Testers are trained to distinguish between manufacturing undulations and structural damage like lumps or bulges in radial ply tyres. Stretched tyres require extra care due to their susceptibility to sidewall damage. Recut tyres are only permitted on specific types of heavier vehicles and passenger vehicles with a higher number of seats.
Tyre Tread Depth: The Legal Minimum
This is one of the most critical tyre checks. The tread pattern consists of grooves designed to provide grip.
- Primary grooves are the main tread grooves, often containing tread wear indicators (TWIs).
- Secondary grooves are shallower and do not count towards the minimum tread depth.
The 'breadth of tread' is the part of the tyre that contacts the road.
Tread Depth Requirements:
| Vehicle Type & First Use Date | Minimum Tread Depth |
|---|---|
| Passenger vehicles (max 8 seats), goods/dual-purpose vehicles (under 3,500kg DGW), tricycles (>410kg ULW), quadricycles (first used on/after 3 Jan 1933) | 1.6mm in primary grooves across the central three-quarters of tread width and circumference. |
| Vehicles first used before 3 Jan 1933, passenger vehicles (>8 seats), tricycles (<410kg ULW, >50cc or electric) | 1.0mm tread visible across the whole tread area and at least 1.0mm depth in a single band across three-quarters of the breadth of tread and circumference. |
| Tricycles (<410kg ULW, <=50cc, petrol) | Visible tread pattern across the whole breadth and circumference (no specific depth required). |
The tread must be visible across the entire tread area for vehicles requiring 1.0mm. If the original tread pattern didn't cover the full width, the 1.0mm requirement applies to the original width.
Tyre Pressure Monitoring System (TPMS)
For M1 vehicles first used on or after 1 January 2012, the TPMS warning lamp is checked. A failure occurs if the lamp clearly indicates a system malfunction, not just low tyre pressure.
Tyre Age: The Hidden Danger
Tyre age is crucial, especially for vehicles with more than 8 passenger seats (excluding historic vehicles). The age is determined by a date code on the sidewall (usually a three or four-digit code, e.g., '3516' means week 35 of 2016).
Tyres over ten years old must be failed if fitted to:
- Any front steered axle.
- Any rear axle of a minibus with single wheel fitment.
Tyres without a date code, or with an illegible code (due to damage or tampering), will also fail. If a date code is not visible on twin wheels, the tester will assume it's present and acceptable, advising the owner.
Retreaded Tyres
Remoulded or retreaded tyres may have multiple date codes. The most recent code dictates the tyre's age. The appearance of these codes can vary.
Frequently Asked Questions (FAQs)
Q1: Can I mix tyres of different brands on the same axle?
Yes, as long as they are of the same size, load rating, speed rating, and structure (e.g., both radial-ply).
Q2: What if my spare tyre has a defect?
Defects on spare tyres are not grounds for MOT failure, but the tester will advise you of the issue.
Q3: Is a small cut on my tyre always a fail?
Not necessarily. Small cuts that do not expose ply or cord, or where cords cannot be felt even when opened, may be acceptable. However, any cut exposing ply or cord is a failure.
Q4: How do I check the age of my tyres?
Look for a DOT marking on the sidewall, followed by a four-digit code (WWYY), where WW is the week and YY is the year of manufacture.
By understanding these detailed requirements, you can ensure your vehicle's wheels and tyres are in optimal condition, leading to a successful MOT test and safer driving for everyone.
If you want to read more articles similar to Decoding Your Car's MOT: Wheels & Tyres, you can visit the Maintenance category.