2021 Mercedes-Benz SLC — MOT failures & pass rate
The 2021 Mercedes-Benz SLC passed 93.5% of its 414 recorded MOT tests. Against coupes & convertibles of a similar age (7.9% fail rate), the 2021 SLC comes out 1.4pp better. Failures cluster in tyres, lighting & signalling and brakes.
What the MOT record shows
No single area dominates — tyres (4.3%) and lighting & signalling (1.7%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are headlamp aim, anti-lock braking system and wipers — headlamp aim alone was recorded 10 times.
Advisories point at the next bill rather than this one: tyres was flagged on 18.4% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 4.3% | 18 |
| 2 | Lighting & signalling | 1.7% | 7 |
| 3 | Brakes | 1.0% | 4 |
| 4 | Suspension | 0.7% | 3 |
| 5 | Emissions & environmental | 0.5% | 2 |
| 6 | Seat belts & restraints | 0.2% | 1 |
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 | 10 |
| 2 | Anti-lock braking system | 2 |
| 3 | Wipers | 2 |
| 4 | Size/type | 2 |
| 5 | Ball joint | 2 |
| 6 | Locking devices | 1 |
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 | 18.4% | 76 |
| 2 | Other defects | 3.6% | 15 |
| 3 | Brakes | 1.7% | 7 |
| 4 | Suspension | 1.7% | 7 |
| 5 | Visibility | 1.5% | 6 |
| 6 | Road wheels | 1.2% | 5 |
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 | 359 | 6.1% |
| 30-60k | 54 | 9.3% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2024 | 194 | 6.2% |
| 2025 | 207 | 7.2% |
What to check before buying a 2021 SLC
On a 2021 SLC, tyres is what the MOT record says goes wrong most — it appeared in 4.3% of tests. Check these areas before you commit.
- Tyres (4.3% 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 (1.7% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (1.0% 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 SLCs pass their MOT?
93.5% of the 414 2021 Mercedes-Benz SLC MOT tests in this dataset passed — a 6.5% fail rate.
What is the most common MOT failure on a 2021 Mercedes-Benz SLC?
Tyres, recorded in 4.3% of tests, followed by lighting & signalling (1.7%).
Does the 2021 SLC get worse with mileage?
Its MOT fail rate rises from 6.1% in the 0-30k band to 9.3% in the 30-60k band.
Methodology & source. Based on 414 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.