10 Most Common MOT Failures in High Wycombe (and How to Avoid Them)

Why So Many Cars Fail Their MOT

Every year, roughly a third of MOT tests in the UK end in failure — and the frustrating part is that most failures aren't caused by expensive mechanical faults. They're caused by small, cheap items that were never checked before the car arrived at the test centre. Lights, tyres and washer fluid account for a huge share of failures we see here in High Wycombe, and every one of them can be checked in your driveway in a few minutes.

Below are the ten defects that cause the most MOT failures, along with what to check before you book your test.

1. Lights & Indicators

Blown bulbs are the single biggest cause of MOT failure in the UK. Headlights, brake lights, indicators, fog lights and number plate lights are all checked. Ask someone to walk around the car while you operate each light, or reverse up to a wall or window to check brake lights.

2. Tyres Below the Legal Limit

Tyres need at least 1.6mm of tread across the central three-quarters of the tyre, all the way round. Sidewall bulges, cuts and exposed cord are also automatic failures. A 20p coin pushed into the tread groove is a quick way to check — if you can see the outer band of the coin, the tread is too low.

3. Windscreen Damage

A chip or crack larger than 10mm within the driver's direct line of sight (roughly the area swept by the wipers, in front of the steering wheel) is an automatic failure. Smaller chips outside this zone are usually fine, but get them looked at before they spread.

4. Suspension Wear

Worn shock absorbers, springs and bushes cause vibration, leaks or clunking noises — and they're a common failure point on older vehicles. This one's harder to check yourself, but a "bounce test" (push down hard on each corner of the car and release) can give you a rough idea; if the car keeps bouncing more than once or twice, get it checked.

5. Brakes

Brake performance is measured on a machine that checks efficiency and balance side-to-side. Worn pads, discs, or a handbrake that doesn't hold on a slope are common causes of failure. If you've noticed grinding, pulling to one side, or a spongy pedal, get it looked at before your test.

6. Washer Fluid & Wipers

An empty washer bottle or wiper blades that smear rather than clear the screen are both instant, easily-avoided failures. Top up your washer fluid and check your wiper blades aren't cracked or split before you book in.

7. Number Plates

Plates must be clean, secure, and use the correct font and spacing. A dirty or partly obscured plate can be enough to fail, so give both plates a wipe down before your test.

8. Exhaust Emissions

Cars must pass an emissions test appropriate to their fuel type. Diesel cars with a blocked or removed DPF (diesel particulate filter) will fail. If your car has been running short journeys only, take it for a longer run on a motorway or A-road before your MOT to help clear the DPF.

9. Seatbelts

Every seatbelt in the car — including the rear ones — is checked for condition and correct latching and retraction. Fraying, cuts or a belt that doesn't lock properly will fail the test.

10. Horn

It sounds trivial, but a horn that doesn't work, or doesn't sound like a horn, is a genuine failure point. It takes two seconds to test — do it before you leave the house.

The 20-Minute Pre-MOT Check

• Test every light, including number plate lights
• Check tread depth on all four tyres (and the spare, if fitted)
• Inspect the windscreen for chips or cracks
• Top up washer fluid and check wiper blades
• Wipe down both number plates
• Test the horn
• Check all seatbelts latch and retract properly
• Look for dashboard warning lights (ABS, airbag, engine management)

If anything on this list needs attention, our full pre-MOT checklist covers each item in more depth. And if you'd rather not do the checks yourself, bring the car to Autoclinics — we're happy to run through everything before you book your test.