2021 MG ZS — MOT failures & pass rate
33,428 MOT tests on the 2021 MG ZS are in this dataset, and 91.0% of them passed. That is 1.9 percentage points worse than small SUVs of a similar age, which fail at 7.2%. Failures cluster in tyres, brakes and lighting & signalling.
What the MOT record shows
No single area dominates — tyres (3.8%) and brakes (2.9%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are tread depth, brake pads and headlamp aim — tread depth alone was recorded 588 times.
Condition tracks the odometer closely. Failures run at 6.8% in the 0-30k band and 13.0% in the 90-120k band, a 6.3-point spread.
Fuel type barely separates them — petrol fails 9.0% of the time against 9.2% for electric.
Brakes is the most common advisory, noted on 18.8% of tests — work that passed today but is likely due soon.
The trend is worsening — 2.2% of tests failed in 2022 against 9.9% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 3.8% | 1,259 |
| 2 | Brakes | 2.9% | 978 |
| 3 | Lighting & signalling | 2.8% | 931 |
| 4 | Visibility | 1.6% | 524 |
| 5 | Suspension | 1.3% | 433 |
| 6 | Steering | 0.3% | 100 |
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 | 588 |
| 2 | Brake pads | 517 |
| 3 | Headlamp aim | 510 |
| 4 | Headlamp | 503 |
| 5 | Brake discs | 373 |
| 6 | Service brake performance | 339 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Brakes | 18.8% | 6,283 |
| 2 | Tyres | 18.7% | 6,243 |
| 3 | Other defects | 8.0% | 2,664 |
| 4 | Suspension | 3.6% | 1,198 |
| 5 | Visibility | 2.1% | 700 |
| 6 | Lighting & signalling | 1.4% | 460 |
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 | 20,434 | 6.8% |
| 30-60k | 11,913 | 12.3% |
| 60-90k | 964 | 15.8% |
| 90-120k | 92 | 13.0% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 21,474 | 9.0% |
| Electric | 11,952 | 9.2% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2022 | 135 | 2.2% |
| 2023 | 680 | 5.4% |
| 2024 | 16,063 | 8.3% |
| 2025 | 16,538 | 9.9% |
What to check before buying a 2021 ZS
The failure pattern for this year is specific enough to inspect against: tyres accounted for 3.8% of tests. Start there.
- Tyres (3.8% 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.
- Brakes (2.9% of tests): Pads/discs are routine wear; binding, imbalance or corroded pipes are more serious — test for pulling under braking. Typical repair: £100–£350 per axle.
- 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.
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 MG ZSs pass their MOT?
91.0% of the 33,428 2021 MG ZS MOT tests in this dataset passed — a 9.0% fail rate.
What is the most common MOT failure on a 2021 MG ZS?
Tyres, recorded in 3.8% of tests, followed by brakes (2.9%).
Does the 2021 ZS get worse with mileage?
Its MOT fail rate rises from 6.8% in the 0-30k band to 13.0% in the 90-120k band.
Methodology & source. Based on 33,428 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.