2021 Mercedes-Benz CLA — MOT failures & pass rate
Across 21,539 MOT tests, the 2021 Mercedes-Benz CLA recorded an 89.7% pass rate. Against small family cars of a similar age (8.3% fail rate), the 2021 CLA comes out 2.0pp worse. Failures cluster in tyres, lighting & signalling and brakes.
What the MOT record shows
Tyres dominates the failure mix at 6.7% of all tests — 4.4 points clear of lighting & signalling, so it is the first thing to check.
At component level the recurring items are headlamp aim, tread depth and brake pads — headlamp aim alone was recorded 474 times.
Mileage matters less than usual here: the 2021 CLA fails 8.1% of the time in the 0-30k band and 6.7% at 120-150k, a spread of only 1.4 points.
Fuel type barely separates them — petrol fails 10.2% of the time against 10.8% for hybrid.
Advisories point at the next bill rather than this one: tyres was flagged on 24.8% of tests without failing them.
The trend is worsening — 6.2% of tests failed in 2023 against 10.6% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 6.7% | 1,432 |
| 2 | Lighting & signalling | 2.3% | 488 |
| 3 | Brakes | 2.1% | 446 |
| 4 | Visibility | 1.9% | 407 |
| 5 | Suspension | 0.6% | 128 |
| 6 | Other defects | 0.4% | 93 |
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 | 474 |
| 2 | Tread depth | 464 |
| 3 | Brake pads | 426 |
| 4 | Wipers | 247 |
| 5 | Washers | 197 |
| 6 | Registration plates | 149 |
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 | 24.8% | 5,337 |
| 2 | Brakes | 11.4% | 2,454 |
| 3 | Other defects | 5.0% | 1,079 |
| 4 | Visibility | 3.9% | 843 |
| 5 | Suspension | 1.6% | 343 |
| 6 | Lighting & signalling | 0.8% | 166 |
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 | 9,160 | 8.1% |
| 30-60k | 10,561 | 11.8% |
| 60-90k | 1,576 | 12.9% |
| 90-120k | 200 | 13.0% |
| 120-150k | 30 | 6.7% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 14,058 | 10.2% |
| Diesel | 4,353 | 10.3% |
| Hybrid | 3,128 | 10.8% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2023 | 423 | 6.2% |
| 2024 | 10,602 | 10.2% |
| 2025 | 10,500 | 10.6% |
What to check before buying a 2021 CLA
On a 2021 CLA, tyres is what the MOT record says goes wrong most — it appeared in 6.7% of tests. Check these areas before you commit.
- Tyres (6.7% 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 (2.3% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (2.1% 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.
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 CLAs pass their MOT?
89.7% of the 21,539 2021 Mercedes-Benz CLA MOT tests in this dataset passed — a 10.3% fail rate.
What is the most common MOT failure on a 2021 Mercedes-Benz CLA?
Tyres, recorded in 6.7% of tests, followed by lighting & signalling (2.3%).
Does the 2021 CLA get worse with mileage?
Its MOT fail rate rises from 8.1% in the 0-30k band to 6.7% in the 120-150k band.
Methodology & source. Based on 21,539 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.