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Diagnostics & EmissionsMost Common MOT Failures in the UK — And How To Avoid Them
13 July 2026 · 5 min read
Suspension faults — the most common reason to fail
According to DVSA data, suspension-related defects account for approximately 38% of MOT failures — making them the single biggest cause of failures across the UK. The most frequent suspension failures include broken or collapsed coil springs, leaking or failed shock absorbers, worn ball joints with excessive play, seized or cracked anti-roll bar drop links, and perished or split rubber bushes in control arms.
What makes suspension failures particularly common is that many owners do not notice gradual wear — a slightly vague ride or a knock over rough ground has often been present for months before an MOT. A tester checking the vehicle on a ramp with a bar finds movement that is invisible on the road. The fix is usually straightforward — a drop link or a pair of shocks is often less than people expect — but leaving worn suspension can cause a tyre to be condemned too, which increases the total bill.
Lighting and electrical faults — second most common
Lighting issues account for around 37% of MOT failures. This includes blown bulbs on headlights, tail lights, brake lights, number plate lights, and fog lights, as well as headlight aim that is set too high or too low, damaged lenses causing beam scatter, and non-functional hazard warning lights or indicators. Daytime running lights that do not operate correctly are an increasingly common failure on newer vehicles.
This is one of the easiest categories to check yourself before an MOT. Walk around the car with the ignition on, activate each circuit — headlights (dip and main beam), indicators (front, rear, and side), brake lights (ask someone to watch while you press the pedal), reverse lights, fog lights, and number plate lights. Fix any bulb failures in advance. A single failed bulb is a major defect under current MOT rules and will fail the test even if everything else passes.
Tyres — worn tread and sidewall damage
Tyre defects appear in roughly a quarter of all MOT failures. The legal minimum tread depth in the UK is 1.6mm across the central three-quarters of the tyre width — but inspectors also check for uneven wear, sidewall bulges, cuts, and exposed cord, all of which cause an immediate failure. A tyre that passes the tread depth check can still fail if the sidewall shows cracks, impact damage, or if there is a significant difference in tread depth across the same axle.
Check tread depth using a 20p coin — if the outer rim of the coin is visible when inserted into the tread groove, the tyre is close to or below the legal limit. We check tread depths on every vehicle that comes through our workshop, and we will always advise you in advance if tyres are borderline so you have time to replace them before your MOT date rather than on the day.
Brakes and advisories — what to expect
Brake faults account for over 10% of failures. Inspectors measure brake efficiency front and rear using a roller brake tester, check pad depth visually, inspect disc condition for scoring and corrosion, and check handbrake operation. Seized callipers, uneven braking efficiency between sides, and brake fluid that has visibly deteriorated are all grounds for a major defect. Contaminated brake fluid — which absorbs moisture over time — is increasingly caught as a major defect category.
Advisories are not failures, but they matter. Common advisories include tyres within a few millimetres of the legal minimum, surface corrosion on brake discs that may spread, and minor play in steering components that is not yet at failure threshold. We explain every advisory clearly after your MOT and give you a realistic view of how long each item is likely to remain within limits so you can plan rather than be surprised at next year's test. Call us on 07498 392333 or book your MOT online at Urban Autohaus, Cornwallis Road, West Bromwich, B70 9BY.