2021 Mercedes-Benz A-Class — MOT failures & pass rate
The 2021 Mercedes-Benz A-Class passed 92.3% of its 65,243 recorded MOT tests. Small family cars of a similar age fail at 8.3%, so the 2021 A-Class sits squarely on the average. Failures cluster in tyres, visibility and lighting & signalling.
What the MOT record shows
Tyres dominates the failure mix at 5.1% of all tests — 3.6 points clear of visibility, so it is the first thing to check.
At component level the recurring items are tread depth, headlamp aim and wipers — tread depth alone was recorded 1,149 times.
Mileage matters less than usual here: the 2021 A-Class fails 6.0% of the time in the 0-30k band and 9.3% at 120-150k, a spread of only 3.4 points.
Split by fuel, hybrid examples fail 1.8pp more often than petrol ones (8.8% vs 7.0%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: tyres was flagged on 21.3% of tests without failing them.
The trend is worsening — 4.8% of tests failed in 2023 against 8.0% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 5.1% | 3,340 |
| 2 | Visibility | 1.5% | 1,003 |
| 3 | Lighting & signalling | 1.3% | 828 |
| 4 | Brakes | 1.1% | 745 |
| 5 | Road wheels | 0.4% | 253 |
| 6 | Suspension | 0.4% | 228 |
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 | 1,149 |
| 2 | Headlamp aim | 867 |
| 3 | Wipers | 713 |
| 4 | Brake pads | 653 |
| 5 | Washers | 389 |
| 6 | Registration plates | 259 |
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 | 21.3% | 13,895 |
| 2 | Brakes | 7.8% | 5,068 |
| 3 | Other defects | 5.0% | 3,244 |
| 4 | Visibility | 3.6% | 2,321 |
| 5 | Suspension | 1.3% | 823 |
| 6 | Road wheels | 0.6% | 376 |
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 | 34,116 | 6.0% |
| 30-60k | 26,709 | 9.5% |
| 60-90k | 3,775 | 9.8% |
| 90-120k | 553 | 13.0% |
| 120-150k | 75 | 9.3% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 34,504 | 7.0% |
| Diesel | 16,877 | 8.2% |
| Hybrid | 13,862 | 8.8% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2023 | 1,447 | 4.8% |
| 2024 | 32,057 | 7.6% |
| 2025 | 31,701 | 8.0% |
What to check before buying a 2021 A-Class
On a 2021 A-Class, tyres is what the MOT record says goes wrong most — it appeared in 5.1% of tests. Check these areas before you commit.
- Tyres (5.1% 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 (1.5% 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.
- Lighting & signalling (1.3% 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 Mercedes-Benz A-Classs pass their MOT?
92.3% of the 65,243 2021 Mercedes-Benz A-Class MOT tests in this dataset passed — a 7.7% fail rate.
What is the most common MOT failure on a 2021 Mercedes-Benz A-Class?
Tyres, recorded in 5.1% of tests, followed by visibility (1.5%).
Does the 2021 A-Class get worse with mileage?
Its MOT fail rate rises from 6.0% in the 0-30k band to 9.3% in the 120-150k band.
Methodology & source. Based on 65,243 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.