MOT failure data · 2025
Smart Forfour MOT problems
Across every Smart Forfour that failed its 2025 MOT, the defect testers recorded most often was tread depth tread depth below requirements of 1.6mm, on 8.92% of failure items. The broadest problem area was tyres at 21.5%. These are recorded defects across the model, not a diagnosis of any one car.
Most common Smart Forfour MOT failures
| # | Recorded defect | Area | Share |
|---|---|---|---|
| 1 | Tread depth tread depth below requirements of 1.6mm | Tyres | 8.92% |
| 2 | Ball joint ball joint excessively worn | Suspension | 7.92% |
| 3 | Catalyst emissions lambda reading after 2nd fast idle outside specified limits | Noise, emissions and leaks | 6.4% |
| 4 | Wipers does not clear the windscreen effectively | Visibility | 5.21% |
| 5 | Coil spring fractured or broken | Suspension | 4.53% |
| 6 | Stop lamp not working | Lamps, reflectors and electrical equipment | 4.14% |
| 7 | Condition has ply or cords exposed | Tyres | 3.77% |
| 8 | Brake pads less than 1.5 mm thick | Brakes | 3.39% |
| 9 | Exhaust system has a major leak of exhaust gases | Body, chassis, structure | 3.3% |
| 10 | Condition has a cut in excess of the requirements deep enough to reach the ply or cords | Tyres | 3.17% |
Shares are of all recorded failure items for this model, so they sum to less than 100% — a single failed test often records several defects, and the long tail below the top 10 is not shown.
What this means if you are buying one
Use it as a viewing checklist. If you are looking at a Smart Forfour, these are the areas worth inspecting and worth asking about — and worth reading the car's own MOT history for, since a defect that keeps reappearing as an advisory is a better signal than any model-wide average.
The MOT record also has hard limits: it does not check the engine, clutch or gearbox, and it says nothing about outstanding finance, insurance write-off history, stolen markers or whether the mileage is genuine. Our used Smart Forfour buying guide covers what to check beyond the MOT.
Checking a specific Smart Forfour?
Enter its registration for finance, write-off, stolen, mileage and keeper history.
Other Smart models
Smart Forfour MOT FAQs
What does a Smart Forfour most commonly fail its MOT on?
The single most recorded defect on Smart Forfour cars failing their 2025 MOT was "tread depth tread depth below requirements of 1.6mm", appearing on 8.92% of failure items.
Does this mean my Smart Forfour will fail?
No. This is what testers recorded across every Smart Forfour that failed in 2025. It shows where this model tends to need attention, not the condition of any individual car. The Smart Forfour passed 78.04% of its initial tests.
How do I see a specific Smart Forfour's MOT history?
Enter its registration on our free MOT history check to see that car's own test results, advisories and recorded mileages.
See also: Smart Forfour MOT pass rate · used Smart Forfour buying guide · free MOT history check
Defect counts from the DVSA MOT Anonymised test-item data for 2025 (class 4 initial tests, failure items only — advisories and minor defects excluded), licensed under the Open Government Licence v3.0.