2021 Mercedes-Benz GLB — MOT failures & pass rate
Across 8,706 MOT tests analysed for the 2021 Mercedes-Benz GLB, the most common recorded failure areas were tyres, brakes and lighting & signalling. Its pass rate of 92.5% was above the average for cars of a similar age (91.2%). Higher-mileage examples failed more often — 14.9% in the 90-120k group versus 5.0% in the 0-30k group.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 4.4% | 380 |
| 2 | Brakes | 1.8% | 154 |
| 3 | Lighting & signalling | 1.3% | 116 |
| 4 | Visibility | 1.1% | 95 |
| 5 | Suspension | 0.4% | 38 |
| 6 | Seat belts & restraints | 0.4% | 32 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Brake pads | 165 |
| 2 | Headlamp aim | 110 |
| 3 | Tread depth | 76 |
| 4 | Wipers | 73 |
| 5 | Registration plates | 38 |
| 6 | Washers | 22 |
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% | 1,853 |
| 2 | Brakes | 12.3% | 1,073 |
| 3 | Other defects | 8.9% | 777 |
| 4 | Visibility | 3.3% | 289 |
| 5 | Suspension | 0.9% | 82 |
| 6 | Seat belts & restraints | 0.3% | 30 |
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 | 4,190 | 5.0% |
| 30-60k | 4,085 | 9.6% |
| 60-90k | 379 | 11.6% |
| 90-120k | 47 | 14.9% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 5,264 | 7.4% |
| Diesel | 3,437 | 7.6% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2023 | 214 | 2.8% |
| 2024 | 4,167 | 6.7% |
| 2025 | 4,316 | 8.5% |
What to check before buying a 2021 GLB
Before buying a 2021 Mercedes-Benz GLB, focus on the areas it most often fails on. Tyres accounted for 4.4% of tests for this year.
- Tyres (4.4% 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 (1.8% 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 (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 GLBs pass their MOT?
92.5% of the 8,706 2021 Mercedes-Benz GLB MOT tests in this dataset passed — a 7.5% fail rate.
What is the most common MOT failure on a 2021 Mercedes-Benz GLB?
Tyres, recorded in 4.4% of tests, followed by brakes (1.8%).
Does the 2021 GLB get worse with mileage?
Its MOT fail rate rises from 5.0% in the 0-30k band to 14.9% in the 90-120k band.
Methodology & source. Based on 8,706 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-01. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.