Smart Forfour MOT failure rate and common faults
22,942 Smart Forfour cars aged 3 to 20 took their MOT in 2025, and 28.1% failed at the first attempt. An average car of the same age failed 24.8% of the time, which makes the Smart Forfour 13% more likely to fail than the typical car on the road. Here is what fails, and which years to look for.
28.1%
failed first time
22,942 MOT tests in 2025
+13%
vs same age average
average car of this age mix: 24.8%
167 of 208
age adjusted rank
among cars; 1 fails least
105.7
dangerous defects per 1,000
same age average: 95.1
What fails on a Smart Forfour MOT
Failure items recorded per 1,000 tests, by part of the car, set against an average car with exactly the same spread of ages. A figure well above average is a weak spot worth checking before you buy.
The most common Smart Forfour MOT failures
The individual failure items testers recorded most often, per 1,000 tests.
| Failure item | Area | Per 1,000 tests |
|---|---|---|
| Tread depth below requirements of 1.6mm | Tyres | 42.8 |
| Ball joint excessively worn | Suspension | 36.3 |
| Wipers: does not clear the windscreen effectively | Windscreen, wipers and mirrors | 33.4 |
| Stop lamp: not working | Lights and electrics | 33.1 |
| Catalyst emissions: Lambda reading after 2nd fast idle outside specified limits | Engine, emissions and leaks | 29.5 |
| Coil spring: fractured or broken | Suspension | 21.3 |
| Washers: provides insufficient washer liquid | Windscreen, wipers and mirrors | 19.2 |
| Tyres: has ply or cords exposed | Tyres | 17.7 |
| Malfunction indicator lamp: inoperative or indicates a malfunction | Engine, emissions and leaks | 17.0 |
| Brake pads: less than 1.5 mm thick | Brakes | 16.4 |
Smart Forfour MOT failure rate by year
Every car fails more often as it ages, so each registration year is compared with the average for all cars of the same age. Years with fewer than 500 tests are left out.
| First registered | Tests | Failed | Same age average | Average mileage |
|---|---|---|---|---|
| 2019 | 1,950 | 19.1% | 16.5% | 31,200 |
| 2018 | 3,785 | 20.5% | 19.1% | 36,600 |
| 2017 | 4,743 | 24.2% | 21.8% | 43,600 |
| 2016 | 5,264 | 29.4% | 25.1% | 49,200 |
| 2015 | 5,418 | 33.9% | 28.1% | 55,700 |
| 2006 | 838 | 44.6% | 43.0% | 96,400 |
| 2005 | 809 | 40.8% | 42.4% | 98,200 |
Advisories to look for in a Smart Forfour's MOT history
An advisory is a tester's warning that something is wearing but has not failed yet. These are the ones written most often on the Smart Forfour, per 1,000 tests. If the car you are looking at has one of these, ask whether it has been fixed since.
- Tread depth: worn close to legal limit/worn on edge293.1
- Tyres: slightly damaged/cracking or perishing161.3
- Brake discs: worn, pitted or scored, but not seriously weakened142.4
- Brake pads: wearing thin62.9
- Brake discs: worn, but not excessively49.0
- Suspension arms: pin or bush worn but not resulting in excessive movement35.7
Checking a used Smart Forfour before you buy
Against cars of the same age, the Smart Forfour fails more often than average on tyres, engine, emissions and leaks and windscreen, wipers and mirrors. Start there.
Tyres
Check the tread across the full width of every tyre, inner edge included. Uneven wear points to worn suspension or out of line steering geometry.
Engine, emissions and leaks
Start the car from cold and watch the exhaust for smoke, look underneath for oil or fuel leaks, and make sure the engine warning light comes on with the ignition and goes out once the engine runs.
Windscreen, wipers and mirrors
Look for chips or cracks in the driver's line of sight, and test the wipers and washers. Windscreen damage in the swept area is an MOT failure.
Averages only take you so far. The specific car's MOT history shows whether it has already failed on any of these, how often advisories were ignored, and whether the mileage climbs steadily from test to test. Read our guide to reading a car's MOT history before you go to view it.
Smart Forfour MOT questions
What is the Smart Forfour MOT failure rate?
28.1% of Smart Forfour cars failed their first MOT test of 2025, from 22,942 tests on vehicles aged 3 to 20. An average car with the same age mix failed 24.8% of the time, so the Smart Forfour was 13% more likely to fail.
What fails most often on a Smart Forfour MOT?
Lights and electrics caused the most failure items, at 123 per 1,000 tests. The single most common failure item was "Tread depth below requirements of 1.6mm", recorded 42.8 times per 1,000 tests.
Which Smart Forfour year has the best MOT record?
Measured against cars of the same age, 2018 registrations did best: 20.5% failed against an average of 19.1% for cars that age. Older cars always fail more often, so compare a year with its age group rather than with newer cars.
Does this tell me whether a particular Smart Forfour will pass?
No. These are averages across every Smart Forfour tested in 2025. The car in front of you has its own record: its full MOT history shows every pass, failure and advisory it has had, and it is free to view by registration.
Other Smart models
- Smart Fortwo28.7% failed
Ranked close to the Smart Forfour
- Volkswagen Beetlerank 164
- Ford Fiestarank 165
- Fiat 500rank 166
- Kia Ceedrank 168
How these figures are calculated
Source: DVSA Anonymised MOT tests and results, 2025 release. We count first tests of cars and small vans (class 4) aged 3 to 20, so a car that fails and is retested is counted once. A failure includes faults fixed and passed within the same visit. The same age average weights the national failure rate for each age by how many Smart Forfour cars of that age were tested, so a model is never penalised for having an older fleet. Make and model are as recorded at the test; trim levels are combined. Full method and rankings.
Contains public sector information licensed under the Open Government Licence v3.0.