Smart Forfour MOT pass rate & common failures
Across 25 model years and 132,497 tests, the Smart Forfour passes its MOT 83.9% of the time. City cars of a similar age fail 14.0% of the time, so this is 2.1pp worse than the group it competes with. Its most common failure areas are tyres, lighting & signalling and visibility.
Best and worst Forfour years
Ranked across Forfour years with at least 1,000 tests. Older cars fail more simply because they are older — compare years close together in age before drawing conclusions.
What the MOT record shows
The strongest year on this record is 2019 (89.7% pass rate); the weakest is 2004 (71.1%). Older cars carry more of the difference than the average implies.
No single area dominates — tyres (6.3%) and lighting & signalling (5.9%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are wipers, tread depth and headlamp aim — wipers alone was recorded 5,639 times.
Condition tracks the odometer closely. Failures run at 9.9% in the 0-30k band and 31.8% in the 150k+ band, a 21.9-point spread — more than double.
The electric cars hold up better: 10.8% fail against 30.7% for diesel, a 19.9-point gap across 3,902 tests.
Tyres is the most common advisory, noted on 25.8% of tests — work that passed today but is likely due soon.
The trend is worsening — 13.6% of tests failed in 2021 against 18.4% in 2025, the usual pattern as a fleet ages.
How it compares
By model year
Every Forfour model year with a usable sample. Years with their own detailed report are linked.
| Year | Tests | Pass rate | Fail rate | Most common failure |
|---|---|---|---|---|
| 2004 | 1,746 | 71.1% | 28.9% | Lighting & signalling |
| 2005 | 4,731 | 73.5% | 26.5% | Lighting & signalling |
| 2006 | 3,568 | 72.8% | 27.2% | Lighting & signalling |
| 2007 | 405 | 72.8% | 27.2% | Lighting & signalling |
| 2008 | 55 | 78.2% | 21.8% | Lighting & signalling |
| 2009 | 75 | 74.7% | 25.3% | Suspension |
| 2010 | 73 | 79.5% | 20.5% | Lighting & signalling |
| 2015 | 33,233 | 81.3% | 18.6% | Lighting & signalling |
| 2016 | 31,122 | 83.3% | 16.7% | Tyres |
| 2017 | 27,402 | 86.1% | 13.9% | Tyres |
| 2018 | 21,308 | 89.0% | 11.0% | Visibility |
| 2019 | 8,738 | 89.7% | 10.3% | Tyres |
Most common failures (all years)
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 6.3% | 8,301 |
| 2 | Lighting & signalling | 5.9% | 7,838 |
| 3 | Visibility | 5.5% | 7,262 |
| 4 | Suspension | 4.3% | 5,770 |
| 5 | Emissions & environmental | 3.2% | 4,190 |
| 6 | Brakes | 3.1% | 4,106 |
| 7 | Body, structure & corrosion | 1.5% | 2,000 |
| 8 | Steering | 0.5% | 655 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Wipers | 5,639 |
| 2 | Tread depth | 5,026 |
| 3 | Headlamp aim | 3,572 |
| 4 | Catalyst emissions | 3,481 |
| 5 | Stop lamp | 3,266 |
| 6 | Ball joint | 3,073 |
| 7 | Washers | 2,833 |
| 8 | Brake pads | 2,240 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 25.8% | 34,157 |
| 2 | Brakes | 17.1% | 22,658 |
| 3 | Suspension | 7.3% | 9,614 |
| 4 | Other defects | 5.9% | 7,883 |
| 5 | Lighting & signalling | 3.8% | 5,090 |
| 6 | Visibility | 3.3% | 4,411 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 51,074 | 9.9% |
| 30-60k | 56,154 | 17.4% |
| 60-90k | 17,044 | 24.1% |
| 90-120k | 5,291 | 27.7% |
| 120-150k | 2,007 | 29.8% |
| 150k+ | 849 | 31.8% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 128,588 | 16.0% |
| Diesel | 1,963 | 30.7% |
| Electric | 1,939 | 10.8% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 24,979 | 13.6% |
| 2022 | 27,128 | 14.6% |
| 2023 | 27,086 | 16.1% |
| 2024 | 26,689 | 17.7% |
| 2025 | 26,615 | 18.4% |
What to check before buying a Smart Forfour
- Tyres (6.3% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Lighting & signalling (5.9% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Visibility (5.5% of tests): Wipers, washers, mirrors and screen damage — usually inexpensive, but check for chips in the driver's line of sight. Typical repair: £15–£150.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
What is the MOT pass rate for the Smart Forfour?
83.9% of the 132,497 Smart Forfour MOT tests in this dataset passed, a 16.1% fail rate, across model years 2001–2025.
What does the Smart Forfour most often fail its MOT on?
Tyres, recorded in 6.3% of tests, then lighting & signalling (5.9%).
Which Forfour years are best and worst for MOT results?
2019 has the best pass rate at 89.7% and 2004 the weakest at 71.1%, from 8,738 and 1,746 tests respectively.
How much does mileage affect Forfour MOT results?
Fail rates run at 9.9% for cars in the 0-30k band and 31.8% for 150k+, a 21.9-point difference.
Is the electric or diesel Forfour more reliable at MOT time?
On MOT-testable defects the electric fails 10.8% of the time against 30.7% for the diesel. This covers testable items only, not engine or gearbox reliability.
Methodology & source. Based on 132,497 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.