2020 Mercedes-Benz GLB — MOT failures & pass rate
The 2020 Mercedes-Benz GLB passed 91.3% of its 8,362 recorded MOT tests. Mid-size SUVs of a similar age fail at 8.8%, so the 2020 GLB sits squarely on the average. Failures cluster in tyres, lighting & signalling and brakes.
What the MOT record shows
Tyres dominates the failure mix at 5.3% of all tests — 3.8 points clear of lighting & signalling, so it is the first thing to check.
At component level the recurring items are tread depth, headlamp aim and brake pads — tread depth alone was recorded 157 times.
Mileage matters less than usual here: the 2020 GLB fails 7.3% of the time in the 0-30k band and 10.0% at 90-120k, a spread of only 2.7 points.
Fuel type barely separates them — diesel fails 8.6% of the time against 9.0% for petrol.
Advisories point at the next bill rather than this one: tyres was flagged on 21.7% of tests without failing them.
The trend is worsening — 2.4% of tests failed in 2022 against 9.3% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 5.3% | 443 |
| 2 | Lighting & signalling | 1.6% | 130 |
| 3 | Brakes | 1.4% | 113 |
| 4 | Visibility | 1.2% | 101 |
| 5 | Seat belts & restraints | 0.9% | 72 |
| 6 | Suspension | 0.6% | 47 |
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 | 157 |
| 2 | Headlamp aim | 135 |
| 3 | Brake pads | 111 |
| 4 | Wipers | 69 |
| 5 | SRS malfunction indicator lamp | 50 |
| 6 | Brake discs | 37 |
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 | 21.7% | 1,811 |
| 2 | Brakes | 11.3% | 942 |
| 3 | Other defects | 7.9% | 660 |
| 4 | Visibility | 3.4% | 284 |
| 5 | Suspension | 1.1% | 89 |
| 6 | Body, structure & corrosion | 0.4% | 35 |
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 | 3,478 | 7.3% |
| 30-60k | 4,255 | 9.3% |
| 60-90k | 546 | 11.5% |
| 90-120k | 70 | 10.0% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 7,366 | 8.6% |
| Petrol | 996 | 9.0% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2022 | 41 | 2.4% |
| 2023 | 2,761 | 8.2% |
| 2024 | 2,765 | 8.5% |
| 2025 | 2,794 | 9.3% |
What to check before buying a 2020 GLB
On a 2020 GLB, tyres is what the MOT record says goes wrong most — it appeared in 5.3% of tests. Check these areas before you commit.
- Tyres (5.3% 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 (1.6% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (1.4% 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 2020 Mercedes-Benz GLBs pass their MOT?
91.3% of the 8,362 2020 Mercedes-Benz GLB MOT tests in this dataset passed — a 8.6% fail rate.
What is the most common MOT failure on a 2020 Mercedes-Benz GLB?
Tyres, recorded in 5.3% of tests, followed by lighting & signalling (1.6%).
Does the 2020 GLB get worse with mileage?
Its MOT fail rate rises from 7.3% in the 0-30k band to 10.0% in the 90-120k band.
Methodology & source. Based on 8,362 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.