2021 BMW Z4 — MOT failures & pass rate
Across 2,396 MOT tests, the 2021 BMW Z4 recorded a 92.7% pass rate. Coupes & convertibles of a similar age fail at 7.9%, so the 2021 Z4 sits squarely on the average. Failures cluster in tyres, lighting & signalling and other defects.
What the MOT record shows
Tyres dominates the failure mix at 5.7% of all tests — 4.8 points clear of lighting & signalling, so it is the first thing to check.
At component level the recurring items are tread depth, headlamp aim and registration plates — tread depth alone was recorded 40 times.
Advisories point at the next bill rather than this one: tyres was flagged on 18.3% of tests without failing them.
The trend is worsening — 1.0% of tests failed in 2023 against 7.3% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 5.7% | 136 |
| 2 | Lighting & signalling | 0.9% | 21 |
| 3 | Other defects | 0.5% | 13 |
| 4 | Visibility | 0.5% | 12 |
| 5 | Road wheels | 0.4% | 10 |
| 6 | Suspension | 0.3% | 8 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Tread depth | 40 |
| 2 | Headlamp aim | 23 |
| 3 | Registration plates | 21 |
| 4 | Washers | 7 |
| 5 | Wipers | 5 |
| 6 | Malfunction indicator lamp | 3 |
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 | 18.3% | 439 |
| 2 | Other defects | 4.9% | 117 |
| 3 | Visibility | 1.5% | 35 |
| 4 | Road wheels | 1.2% | 28 |
| 5 | Suspension | 0.8% | 18 |
| 6 | Brakes | 0.5% | 12 |
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 | 1,930 | 6.3% |
| 30-60k | 438 | 11.0% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2023 | 103 | 1.0% |
| 2024 | 1,146 | 7.8% |
| 2025 | 1,138 | 7.3% |
What to check before buying a 2021 Z4
On a 2021 Z4, tyres is what the MOT record says goes wrong most — it appeared in 5.7% of tests. Check these areas before you commit.
- Tyres (5.7% 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 (0.9% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Other defects (0.5% of tests): Miscellaneous items not in the main categories. Typical repair: varies.
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 BMW Z4s pass their MOT?
92.7% of the 2,396 2021 BMW Z4 MOT tests in this dataset passed — a 7.3% fail rate.
What is the most common MOT failure on a 2021 BMW Z4?
Tyres, recorded in 5.7% of tests, followed by lighting & signalling (0.9%).
Does the 2021 Z4 get worse with mileage?
Its MOT fail rate rises from 6.3% in the 0-30k band to 11.0% in the 30-60k band.
Methodology & source. Based on 2,396 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.