An MOT is required to ensure that a car is legally safe to drive on the UK roads and it tests many aspects of the vehicle including the body condition, tyres, windscreen, seatbelts, registration plates, and brakes. So what are the most common reasons why cars fail an MOT test? And what can be done to prevent this on your own vehicle?
In this guide, we’ll take a deep dive into the most common MOT fails and how to prevent them.
Top 5 MOT Fail Reasons
- Lights (18-26% of fails)
- Suspension (13-21% of fails)
- Brakes (10-12% of fails)
- Tyres (7-11% of fails)
- Driver’s View Impaired (6-13% of fails)
This data is referenced from the following sources: gov.uk (2015), rac.co.uk (2022) and motdata.uk (2024).
Lights (18-26%)
The biggest reason why cars fail their MOT tests is due to issues with the lights. The most common cause (accounting for around 18% of all fails) simply being a blown bulb, which fortunately is cheap and easy to rectify. Here are the common causes of an MOT failure resulting from a light fault:
- Blown bulbs
- Incorrectly aligned headlights
- Broken or discoloured lenses
- Dashboard warning lights remaining on
How to Avoid It
Running a series of quick checks can help to address any issues which could result in an MOT failure, giving you a chance to fix them before the test.
- Activate your headlights, full beam, brake lights, fog lights, tail lights, daytime running lights, registration plate lamps and indicator lights with someone stood outside the vehicle to confirm if they are working properly.
- Ensure the headlights are correctly aligned so that they don’t dazzle oncoming drivers.
- Check the condition of the plastic light covers for any water ingress, haze or cracks, and replace if necessary.
- Ensure all the lights are clean and aimed correctly.
- Check that the lights are the correct colour and intensity, and that the pairs are matching.
- Make sure that the dashboard warning lights do not stay illuminated, and investigate if needed.
Suspension (13-21%)
The second most common reason for an MOT fail is due to issues with the suspension, these can include:
- Fractured springs
- Leaking shock absorbers
- Worn suspension brushes
Issues with the suspension can cause unstable handling and uneven tyre wear.
How to Avoid It
This MOT fail can be harder to avoid as it’s not something that can be as easily checked as a blown bulb for example. Getting your car regularly serviced and inspected, and considering booking in for an annual service shortly before the MOT test is due, is a good idea to prevent any suspension-related failures.
Given the condition of many UK roads, it may come as no surprise that the amount of suspension-related MOT failures has risen from around 13% of fails (according to the RAC) to 21% (according to MOT Data) from 2022-2024. Sadly, dealing with potholes is a part of driving, and it’s important to check the vehicle if you have been unfortunate enough to encounter one – particularly at speed.
If you do hit a pothole, pay attention to any unusual noises made by the car afterwards. Also, park it up and make sure it sits level and that there are no issues with the wheels or tyres.
Brakes (10-12%)
During an MOT test, the braking system will be assessed both visually and using a roller brake test, and roughly 1 in 10 vehicles will fail due to issues with their brakes. The main problems are:
- Worn brake pads – the minimum pad thickness is 1.5mm in the UK, but it recommended to replace the pads when they reach 3mm.
- Worn brake discs – different manufacturers specify the acceptable wear limit so the exact measurement varies between vehicles.
These are one of the more expensive issues on this list, and the cost to replace worn brake pads and discs varies massively between manufacturers. Fortunately, they don’t need replacing too often, and typically last between 30,000 and 60,000 miles; the exact frequency is dependent on the pad materials and driving habits.
How to Avoid It
- Book your car in for a brake check or service and inspection prior to the MOT to ensure the brakes are functioning correctly and replace any parts if necessary.
- Listen for any squeaking or grinding noises when applying the brakes as these are common signs of thin brake pads which could result in an MOT fail.
Tyres (7-11%)
The tyres are one of the highest-wearing components of a vehicle, and one of the most important to ensure the car is safe to drive. The tyres are assessed thoroughly on an MOT test, and the following issues will result in a fail result:
- Worn tread – in the UK the tread needs to measure at least 1.6mm across the central three quarters of the width, and the entire circumference. It is recommended to change the tyres when the tread depth reaches 3mm.
- Cuts or damage – smaller nicks are usually passable, but anything in excess of the requirements deep enough to reach the ply or cords will result in an MOT fail.
- Bulges – this happens due to internal damage, and is often a result of hitting a pothole or debris at speed. A tyre with a budge will need replacing immediately.
How to Avoid It
- Place a 20p coin in the tread, and ensure you cannot see the outer band as this indicates the tread is too low. If you can, make sure to replace the tyres immediately. Also ensure you do this on all four tyres across the full width.
- Check that the load index and speed rating of the tyres is correct for the vehicle. The vehicle requirements can be found in the handbook, and the ratings can be found on the side of the tyre.
- Check that the tyre pressure is correct. You can do this at a petrol station, or take your car to your local tyre fitter.
- Ensure that the tyres don’t have cuts or bulges, and replace them if you see any signs of damage.
Driver’s View (6-13%)
Issues affecting the driver’s view of the road can refer to a whole host of problems including;
- Things blocking visibility through the windscreen e.g. chips or cracks in the glass, or even sat-navs and dashcams.
- Worn windscreen wipers.
- Insufficient windscreen wiper fluid or a faulty pump.
How to Avoid It
- Check the windscreen and other windows for cracks, and repair or replace as needed.
- Make sure the wing mirrors and rear-view mirrors are clean and free from damage.
- Check the windscreen wiper looks in good condition. Most need replacing annually.
- Fill the windscreen washer reservoir and test that the pump is working.
- Make sure nothing is blocking the windscreen e.g. stickers, air fresheners, dash-cams etc.
Book an MOT in Worcester
Here at Recharged Automotive in Worcester, we have over 30 years of experience MOT testing and servicing vehicles. Get in touch today by calling 01905 458156.
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