Around 28% of cars fail their MOT at the first attempt, and more than 80% of those failures come from just five categories. Almost all of them are preventable with a ten-minute check the week before.
What the DVSA data shows
Every MOT result in Great Britain is recorded and published. It is the largest honest dataset there is on the condition of cars actually on the road — not what owners say about their car, but what a tester found when they put it on a ramp.
| Category | Share of failures | Typical cost to fix | Preventable? |
|---|---|---|---|
| Lighting and signalling | 19.9% | £5–£120 | Almost always |
| Suspension | 19.8% | £150–£600 | Sometimes |
| Brakes | 19.6% | £120–£500 | Often |
| Tyres | 12.0% | £60–£180 each | Always |
| Driver’s view of the road | 9.8% | £15–£250 | Almost always |
The striking thing is how many failures are trivial. A blown bulb costs a few pounds and fails an MOT exactly as thoroughly as a seized brake caliper.
1. Lighting and signalling — 19.9%
The single biggest cause, and the cheapest to avoid. Bulbs, alignment, cracked lenses and number plate lights. Walk around the car with the lights on and get someone to press the brake pedal. Two minutes.
Worth knowing: bulbs are consumables and no warranty covers them. But if a light circuit keeps failing, the fault is usually a control module or wiring — and that generally is covered.
2. Suspension — 19.8%
Springs, shock absorbers, bushes and ball joints. Britain’s roads are hard on suspension, and potholes account for a great deal of this. Listen for knocking over bumps and check for uneven tyre wear.
3. Brakes — 19.6%
Worn pads and discs, imbalance, corroded lines, seized calipers. Pads and discs are wear items you pay for yourself. Hydraulic failures and ABS faults are usually a different matter.
4. Tyres — 12.0%
Tread below 1.6mm across the central three-quarters, damage, or the wrong type fitted. The 20p test takes seconds: if the outer band of the coin is visible when inserted into the tread, you are probably below the limit.
5. Driver’s view of the road — 9.8%
Wipers, washers, chips in the swept area of the windscreen, obstructions. A chip larger than 10mm directly in front of the driver is a failure. Most are repairable for far less than a new screen if caught early.
An MOT tests roadworthiness. It says almost nothing about the engine, gearbox, turbocharger, or hybrid and EV drive systems — the components that produce four-figure bills. A car can pass its MOT on a Monday and need a £2,000 gearbox on the Friday. That gap is exactly what a mechanical breakdown warranty exists to fill.
The ten-minute pre-MOT check
- All lights, including brake, reverse, fog and number plate
- Tyre tread and pressures, all five including the spare
- Wipers for splitting, and washer fluid topped up
- Windscreen chips in the driver’s line of sight
- Horn
- Seatbelts — pull each one sharply, it should lock
- Mirrors secure and undamaged
- Number plates clean and readable
- Any warning light still lit on the dashboard
- Oil and coolant levels
Doing this reliably removes about half your risk of a first-time failure.
