I’m a car expert… here’s the 10 ways to avoid failing an MOT test

CAR experts have revealed the most common causes a vehicle will fail an MOT test – and some in the top 10 will likely surprise you.

Experts at insurance broker One Sure Insurance crunched the numbers from the DVLA’s MOT database to find the most common causes among Class 4 motors, which includes cars, vans, motorhomes and other smaller commercial vehicles.

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Securing the top spot in the list were worn or damaged tyres.

The experts found that across all four tyres, poor condition, or not meeting the legal requirement of at least 1.6mm of tread depth accounted for 1,101,839 MOT failures in the UK in just one year.

The driver-side front tyre tread depth accounted for more than a quarter of these – 368,853 MOT failures.

Accounting for 1,069,069 MOT failures was damaged coil springs, located in your car’s suspension, enough to secure it the second spot on the list.

Britain’s roads are plagued with potholes 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.

Taking third place was headlamp aim, which was 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.

There are a number of reasons why headlights can become mis-aligned, including damage to the fittings or headlight bulbs simply expanding with age on older cars.

In this category, the projected beam being incorrect is the leading cause of failure, accounting for 433,681 MOT failures.

Coming in fourth place was windscreen wipers, which made up 778,244 MOT failures, with almost every case of failure being down to the wipers not clearing the windscreen effectively.

That reason accounted for 751,881 MOT failures in that category.

Position lamps, or more commonly known as sidelights, made fifth place, making up 759,032 MOT failures.

Used to indicate the size and the position of a car, non-working position lamps make up the bulk of the failures within this category, having caused 710,180 MOT failures.

In sixth place are brake pads, which caused 674,986 MOT failures.

The leading cause of failure within this category is made up almost entirely being down to brake pads being less than 1.5mm thick, which accounted for 615,077 of these MOT failures.

Issues with pins and bushes, took seventh place, which caused 632,061 MOT failures.

Most failures in this category were due to pins or bushes being excessively worn at the front of the vehicle, resulting in 467,118 of these MOT failures.

Bushes act as small protective pads fitted to various parts of the suspension system, and pins – sometimes known as swivel pins, or kingpins – are the main pivot in the steering mechanism of a car or other vehicle.

Ball joints allow suspension movement which maximizes the tyre’s contact with the road providing optimum vehicle control and tire wear.

They also take eighth place on the list, having caused 620,900 MOT failures.

Many original equipment ball joints are designed as sealed units.

If the protective boot fails, water and road debris will quickly cause wear and ball joint failure.

Ninth place goes to service brake performance.

Otherwise known as the braking system in a vehicle, inadequate service brake performance has resulted in 615,329 MOT failures.

In tenth spot are issues with the rigid brake pipes which caused 522,429 MOT failures.

These pipes are used to transfer pressurised brake fluid from the master cylinder to the brake hoses and are especially susceptible to corrosion.

Excessively corroded rigid brake pipes accounted for 143,600 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 out 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.

A spokesperson for One Sure Insurance said: “The research sheds light on critical areas of concern for vehicle owners.

“The results can be helpful for drivers who want to keep their vehicles in good condition and pass the MOT inspection with flying colours.

“It’s essential for all drivers to take note of these findings and address any potential issues before an inspection.

“This proactive approach can help drivers avoid expensive repairs in the future and keep their cars running safely on the road.”

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