2021 SEAT Mii — MOT failures & pass rate
The 2021 SEAT Mii passed 90.5% of its 2,398 recorded MOT tests. All cars of a similar age fail at 8.6%, so the 2021 Mii sits squarely on the average. Failures cluster in tyres, lighting & signalling and suspension.
What the MOT record shows
No single area dominates — tyres (5.8%) and lighting & signalling (2.8%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are headlamp aim, washers and linkage ball joints — headlamp aim alone was recorded 41 times.
Advisories point at the next bill rather than this one: tyres was flagged on 19.6% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 5.8% | 139 |
| 2 | Lighting & signalling | 2.8% | 68 |
| 3 | Suspension | 2.1% | 50 |
| 4 | Visibility | 1.7% | 41 |
| 5 | Brakes | 1.1% | 27 |
| 6 | Seat belts & restraints | 0.2% | 5 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 41 |
| 2 | Washers | 30 |
| 3 | Linkage ball joints | 29 |
| 4 | Service brake performance | 20 |
| 5 | Registration plate lamp(s) | 18 |
| 6 | Shock absorbers | 15 |
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 | 19.6% | 470 |
| 2 | Other defects | 5.4% | 130 |
| 3 | Brakes | 4.3% | 103 |
| 4 | Suspension | 2.6% | 62 |
| 5 | Visibility | 1.7% | 40 |
| 6 | Lighting & signalling | 0.3% | 8 |
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 | 1,936 | 8.7% |
| 30-60k | 447 | 12.3% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2024 | 1,204 | 10.1% |
| 2025 | 1,169 | 8.8% |
What to check before buying a 2021 Mii
On a 2021 Mii, tyres is what the MOT record says goes wrong most — it appeared in 5.8% of tests. Check these areas before you commit.
- Tyres (5.8% 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 (2.8% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (2.1% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
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 SEAT Miis pass their MOT?
90.5% of the 2,398 2021 SEAT Mii MOT tests in this dataset passed — a 9.5% fail rate.
What is the most common MOT failure on a 2021 SEAT Mii?
Tyres, recorded in 5.8% of tests, followed by lighting & signalling (2.8%).
Does the 2021 Mii get worse with mileage?
Its MOT fail rate rises from 8.7% in the 0-30k band to 12.3% in the 30-60k band.
Methodology & source. Based on 2,398 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.