Tyres are one of the most common reasons vehicles fail their MOT, yet many problems can be spotted long before test day. This guide breaks down the key tyre-related fail points—tread depth, structural damage, and incorrect sizing—so you know exactly what to look for. Stay safe, avoid retests, and make informed decisions before heading to the garage.
There are several key areas of a vehicle that get checked during its annual MOT – with any one of these resulting in an overall failure, should the component not be up to scratch.
When you fail an MOT, the vehicle is not deemed safe to drive on the road until the issue has been repaired and rectified. You are only legally allowed to drive the vehicle to a garage for the required repairs, and then to an MOT centre for a re-test.
If you pass your MOT, the vehicle has been deemed safe to drive under the legal limits imposed by this annual check – though you may find that different areas are flagged for attention.
In this article, we’re looking specifically at the kind of tyre issues that can cause a vehicle to fail its MOT – and the checks that you can carry out on your own vehicle prior to taking it for its MOT.
1. Tread Depth
The minimum tread depth for a vehicle’s tyre is 1.6mm.
If you take your vehicle for an MOT and its tyres are found to have a tread depth which falls below this 1.6mm legal limit, then you will automatically fail the MOT test.
This is because the legal limit is there to ensure that vehicles are safe to drive on the road, and that the driver has good control especially when steering or braking. As the tread depth on a tyre wears down, the stopping distance when using the brakes gets longer, and steering becomes less responsive.
2. Bulges and Cracks
If your vehicle is found to have significant bulges and cracks in its outer wall, then this indicates concealed damaged within the structure of the tyre.
Even if this is not affecting the immediate use of the tyre, the assumption is that this kind of damage increases the likelihood of a blowout or damage the next time the tyre hits a pothole or obstacle in the road.
For safety, this kind of visible damage will result in an MOT fail – with the damaged tyre or tyres needing to be replaced.
3. Tyre Size
If you look at the sidewall of your tyre, you will see a series of markings, letters and numbers printed on the rubber.
Some of this refers to the tyre size – its load rating, speed rating, and other calculations.
If this is found to be insufficient or incorrect according to your vehicle type, then it could lead to a failure at your next MOT. The tyres fixed to your vehicle need to have the right structure to hold the weight of the vehicle and to match the speed of the vehicle, or you risk a higher chance of an accident, loss of control, or significant damage to the tyre on the road.
While we’re on this topic, it’s also important for the tyre size to be equal across the vehicle. If different tyre sizes or types are found on the same vehicle, this increases the risk of an imbalanced response when steering, braking, or simply when it comes to managing and tracking wear and tear.
To cut a long story short, tyres need to match across the vehicle – and be sized correctly.
