1981 MG B — MOT failures & pass rate
The 1981 MG B passed 83.0% of its 843 recorded MOT tests. All cars of a similar age fail at 17.3%, so the 1981 B sits squarely on the average. Failures cluster in lighting & signalling, emissions & environmental and brakes.
What the MOT record shows
No single area dominates — lighting & signalling (8.9%) and emissions & environmental (7.5%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are non catalyst emissions, washers and position lamp — non catalyst emissions alone was recorded 75 times.
A 90-120k example is materially riskier than a 0-30k one: 8.8% versus 15.7%.
Advisories point at the next bill rather than this one: emissions & environmental was flagged on 18.6% of tests without failing them.
The trend is improving — the fail rate fell from 17.6% in 2021 to 16.1% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 8.9% | 75 |
| 2 | Emissions & environmental | 7.5% | 63 |
| 3 | Brakes | 5.8% | 49 |
| 4 | Visibility | 5.0% | 42 |
| 5 | Body, structure & corrosion | 2.9% | 24 |
| 6 | Suspension | 2.5% | 21 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Non catalyst emissions | 75 |
| 2 | Washers | 37 |
| 3 | Position lamp | 31 |
| 4 | Service brake performance | 25 |
| 5 | Headlamp aim | 24 |
| 6 | Rear fog lamp | 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 | Emissions & environmental | 18.6% | 157 |
| 2 | Suspension | 18.3% | 154 |
| 3 | Brakes | 9.4% | 79 |
| 4 | Other defects | 4.7% | 40 |
| 5 | Steering | 4.2% | 35 |
| 6 | Body, structure & corrosion | 4.0% | 34 |
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 | 235 | 15.7% |
| 30-60k | 245 | 18.8% |
| 60-90k | 306 | 18.0% |
| 90-120k | 57 | 8.8% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 284 | 17.6% |
| 2022 | 191 | 19.4% |
| 2023 | 140 | 15.0% |
| 2024 | 116 | 14.7% |
| 2025 | 112 | 16.1% |
What to check before buying a 1981 B
On a 1981 B, lighting & signalling is what the MOT record says goes wrong most — it appeared in 8.9% of tests. Check these areas before you commit.
- Lighting & signalling (8.9% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Emissions & environmental (7.5% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
- Brakes (5.8% 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.
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 1981 MG Bs pass their MOT?
83.0% of the 843 1981 MG B MOT tests in this dataset passed — a 17.0% fail rate.
What is the most common MOT failure on a 1981 MG B?
Lighting & signalling, recorded in 8.9% of tests, followed by emissions & environmental (7.5%).
Does the 1981 B get worse with mileage?
Its MOT fail rate rises from 15.7% in the 0-30k band to 8.8% in the 90-120k band.
Methodology & source. Based on 843 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.