1978 Triumph Stag MOT Pass Rate
Pass rate for Stag models manufactured in 1978, based on 1,598 real MOT test results.
Data from official DVSA MOT testing records
This page shows all Stag cars tested in 1978. Want to see how cars built in 1978 hold up over time?
View 1978 Triumph Stag vintage page → (73.1% current pass rate)1978 Triumph Stag MOT Analysis
The 1978 Triumph Stag has an MOT pass rate of 67.8% based on 1,598 tests — slightly above the UK average for UK vehicles. Cars of this vintage present for MOT with an average of 56,698 miles on the odometer. With a 32.2% failure rate, the 1978 Stag is rated as "Good" for MOT reliability.
The leading cause of MOT failure for the 1978 Triumph Stag is Lamps, reflectors and electrical equipment, responsible for 1.0% of failures. Lighting failures cover all external lights: headlights, tail lights, brake lights, indicators, fog lights, and reflectors. A single blown bulb will cause an MOT fail. This is one of the most preventable failure categories. Typical repair costs range from £5–50. Noise, emissions and leaks is the second most common issue at 0.9%. Brakes follows at 0.7%.
Top failures specific to 1978 models only. The overall Stag page may show different rankings.
What Fails Most
What Fails on This Car?
Click a category to see specific failure items.
View as table
| Rank | Failure Category | Rate (%) | Count |
|---|---|---|---|
| 1 | Lamps, Reflectors And Electrical Equipment | 1.0% | 16 |
| 2 | Noise, Emissions And Leaks | 0.9% | 15 |
| 3 | Brakes | 0.7% | 11 |
| 4 | Steering | 0.2% | 3 |
| 5 | Visibility | 0.2% | 3 |
| 6 | Seat Belts And Supplementary Restraint Systems | 0.1% | 2 |
| 7 | Suspension | 0.1% | 2 |
| 8 | Tyres | 0.1% | 1 |
| 9 | Non-component Advisories | 0.1% | 1 |
Failures per 10,000 Miles
avg. 56,698 miFor every 10,000 miles driven, this shows what percentage of MOT tests fail for each category. This accounts for how far cars are actually driven, not just raw pass/fail counts.
View as table
| Category | Rate / 10K mi | Raw % | Count |
|---|---|---|---|
| Lamps & Electrical | 0.18 | 1.0% | 16 |
| Noise, emissions and leaks | 0.17 | 0.9% | 15 |
| Brakes | 0.12 | 0.7% | 11 |
| Steering | 0.03 | 0.2% | 3 |
| Visibility | 0.03 | 0.2% | 3 |
| Seat Belts | 0.02 | 0.1% | 2 |
| Suspension | 0.02 | 0.1% | 2 |
| Tyres | 0.01 | 0.1% | 1 |
| Non-component advisories | 0.01 | 0.1% | 1 |
Mileage Statistics
Mileage-adjusted failure rate — accounts for how much this model year is typically driven.
About This Data
The 1978 Triumph Stag has an MOT pass rate of 67.8% based on 1,598 tests — slightly above the UK average for UK vehicles. Cars of this vintage present for MOT with an average of 56,698 miles on the odometer. With a 32.2% failure rate, the 1978 Stag is rated as "Good" for MOT reliability.
If you own or are considering buying a 1978 Triumph Stag, you can expect reliable MOT performance overall. Before your MOT, pay particular attention to lamps, reflectors and electrical equipment: Walk around the car and check every light — headlights (dipped and main beam), side lights, tail lights, brake lights, indicators, hazard lights, reverse light, rear fog light, and number plate lights. Replace any blown bulbs before the test. At 56,698 average miles, these vehicles are in the mid-range where component wear starts to become a factor.
Lamps, reflectors and electrical equipment — 1.0% of failures
Lamps, reflectors and electrical equipment issues account for 1.0% of MOT failures on 1978 Triumph Stag models. Lighting failures cover all external lights: headlights, tail lights, brake lights, indicators, fog lights, and reflectors. A single blown bulb will cause an MOT fail. This is one of the most preventable failure categories. Typical repair costs: £5–50. Pre-MOT check: Walk around the car and check every light — headlights (dipped and main beam), side lights, tail lights, brake lights, indicators, hazard lights, reverse light, rear fog light, and number plate lights. Replace any blown bulbs before the test.
Noise, emissions and leaks — 0.9% of failures
Noise, emissions and leaks issues account for 0.9% of MOT failures on 1978 Triumph Stag models. Emissions failures occur when exhaust gases exceed legal limits for carbon monoxide (CO), hydrocarbons (HC), or particulate matter (diesel). Common causes include faulty oxygen sensors, clogged catalytic converters, or DPF issues on diesel vehicles. Typical repair costs: £100–1,000+. Pre-MOT check: If the engine management light is on, get it diagnosed before the MOT. For diesel cars, ensure the DPF has completed a regeneration cycle. Regular servicing and using premium fuel before the test can help.
Brakes — 0.7% of failures
Brakes issues account for 0.7% of MOT failures on 1978 Triumph Stag models. Brake-related failures include worn brake pads, corroded brake discs, leaking brake lines, and faulty brake servos. These are safety-critical components — any brake deficiency will result in an MOT fail. Typical repair costs: £150–400. Pre-MOT check: Listen for squealing or grinding noises. Check brake pedal feel — if it feels spongy or goes to the floor, have the system inspected immediately. Look at brake pad thickness through the wheel spokes (minimum 3mm).
Based on DVSA anonymised MOT test data (2005–2024). Crown copyright, Open Government Licence v3.0.