2021 Smart Eq Forfour — MOT failures & pass rate
Across 712 MOT tests analysed for the 2021 Smart Eq Forfour, the most common recorded failure areas were tyres, visibility and lighting & signalling. Its pass rate of 90.3% was in line with the average for cars of a similar age (91.2%).
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 6.5% | 46 |
| 2 | Visibility | 6.3% | 45 |
| 3 | Lighting & signalling | 2.3% | 16 |
| 4 | Brakes | 0.8% | 6 |
| 5 | Suspension | 0.6% | 4 |
| 6 | Seat belts & restraints | 0.1% | 1 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Wipers | 42 |
| 2 | Washers | 15 |
| 3 | Headlamp aim | 12 |
| 4 | Size/type | 5 |
| 5 | Tread depth | 5 |
| 6 | Service brake performance | 4 |
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 | 17.1% | 122 |
| 2 | Brakes | 8.4% | 60 |
| 3 | Other defects | 4.9% | 35 |
| 4 | Visibility | 4.5% | 32 |
| 5 | Suspension | 1.3% | 9 |
| 6 | Road wheels | 0.3% | 2 |
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 | 667 | 9.6% |
| 30-60k | 45 | 11.1% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2024 | 347 | 8.1% |
| 2025 | 359 | 11.1% |
What to check before buying a 2021 Eq Forfour
Before buying a 2021 Smart Eq Forfour, focus on the areas it most often fails on. Tyres accounted for 6.5% of tests for this year.
- Tyres (6.5% 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.
- Visibility (6.3% 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.
- Lighting & signalling (2.3% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£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
How many 2021 Smart Eq Forfours pass their MOT?
90.3% of the 712 2021 Smart Eq Forfour MOT tests in this dataset passed — a 9.7% fail rate.
What is the most common MOT failure on a 2021 Smart Eq Forfour?
Tyres, recorded in 6.5% of tests, followed by visibility (6.3%).
Does the 2021 Eq Forfour get worse with mileage?
Its MOT fail rate rises from 9.6% in the 0-30k band to 11.1% in the 30-60k band.
Methodology & source. Based on 712 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-01. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.