Insurance broker One Sure Insurance analysed the DVLA’s MOT database to find the most common causes of MOT failure among Class 4 vehicles (Cars, vans, motorhomes, and other smaller commercial vehicles).
It will come as no great surprise to anyone in the trade that taking first place as the most common reason for a car to fail its MOT are worn or damaged tyres. Across all four tyres, poor condition, or not meeting the legal requirement of at least 1.6mm of tread depth contributed to 1,101,839 MOT failures across the UK in a single year. The driver-side front tyre tread depth accounted for more than a quarter of these, the equivalent of 368,853 MOT failures.
In second place, the cause of 1,069,069 MOT failures are damaged coil springs located in your car’s suspension. Britain’s roads aren’t the smoothest, to put it mildly, and the car’s suspension tends to take the brunt of any potholes and speedbumps that road users might encounter on their travels. Fractured or broken front passenger side coil springs accounted for 346,383 of MOT failures in this category.
Headlamp aim takes third place, as the cause of 806,993 MOT failures. Headlamp aim being incorrect, too high or too low, can impact visibility not just for the driver but other users on the road. Headlights can become mis-aligned for several reasons, including damage to the fittings or headlight bulbs simply expanding with age on older cars. The projected beam being incorrect is the leading cause of failure in this category, accounting for 433,681 MOT failures.
Windscreen wipers take fourth place, having caused 778,244 MOT failures, with almost every case of failure being down to the wipers not clearing the windscreen effectively.
Position lamps take the fifth spot. Known more commonly as sidelights, non-road safe position lamps have caused 759,032 MOT failures. Brake pads take sixth place, being the cause of 674,986 MOT failures. The leading cause of failure within this category is almost entirely brake pads being less than 1.5mm thick, resulting in 615,077 of these MOT failures.
Interestingly, the driver’s side tyre depth being below 1.6mm is the single most significant cause for failure of an MOT, with 368,853 MOT failures. According to a YouGov poll, Britons are most likely to change their tyres only when it is absolutely necessary. Three in five car owners (60 per cent) switch them only when carrying on using them becomes untenable, which helps explain why they are the biggest cause of an MOT failure.
The study also found that of the 38,155,866 MOT tests carried out on all classes of vehicles in 2021, almost one in five resulted in failure.
|Rank||Fault Category||Number of Faults|
|7||Pins and bushes||632,061|
|9||Service brake performance||615,329|
|10||Rigid brake pipes||522,429|