MOT performance
MOT failure “Rbt (sp): efficiency less than 50% of the required value”: how common it is and which cars get it
“Rbt (sp): efficiency less than 50% of the required value” (dangerous defect, brakes) was recorded as a failure on 0.28% of UK MOT tests in 2023–2024: 185,735 tests, the number 48 most common failure item. It is 8.7 times as common at 10 years old (0.26%) as at 3 (0.03%). It is most common at 18 years old (0.83% of tests).
185,735 tests with this failure, 2023–2024
Check a specific car's MOT history and running costsAt a glance
| Figure | Value | Basis |
|---|---|---|
| Share of MOT tests | 0.28% | 185,735 tests, 2023–2024 |
| Rank among failure items | #48 | by number of tests |
| Most common at | 18 years old | 0.83% of tests at that age |
| Models compared | 341 | models with enough tests |
How it changes with age
By fuel
Diesel: 0.38% of tests; Petrol: 0.23% of tests; Electric: 0.07% of tests; Hybrid: 0.07% of tests. Fuel groups differ in age and mileage, so these raw shares are not like-for-like; the model tables below are.
Models that fail on it most often
Relative to cars of the same age and fuel (1.00 = national rate for this item). Only models with enough tests for the difference to be clear are ranked.
| Model | Tests | Failed on it | vs similar cars |
|---|---|---|---|
| Ford Mustang | 23,925 | 1.27% | +817% |
| Hyundai ix20 | 58,240 | 1.11% | +630% |
| Hyundai Coupe | 13,208 | 3.55% | +560% |
| Volkswagen Amarok | 42,466 | 1.00% | +484% |
| Volkswagen Crafter | 13,028 | 2.22% | +484% |
| Hyundai i800 | 16,542 | 1.25% | +458% |
| Chrysler Grand Voyager | 10,029 | 4.04% | +451% |
| Vauxhall Tigra | 15,029 | 2.90% | +438% |
| Ford EcoSport | 200,751 | 0.28% | +429% |
| Hyundai ix35 | 104,677 | 1.61% | +406% |
Models that fail on it least often
| Model | Tests | Failed on it | vs similar cars |
|---|---|---|---|
| Porsche Macan | 56,741 | 0.00% | -100% |
| Lexus NX | 53,608 | 0.00% | -100% |
| Audi A7 | 33,889 | 0.01% | -97% |
| Mercedes-Benz GLC | 150,770 | 0.00% | -97% |
| Tesla Model S | 21,398 | 0.01% | -97% |
| Audi Q5 | 213,847 | 0.01% | -95% |
| Volvo XC60 | 216,923 | 0.01% | -93% |
| Volkswagen CC | 28,379 | 0.03% | -91% |
| Audi A5 | 253,626 | 0.02% | -91% |
| Lotus Elise | 10,204 | 0.05% | -90% |
Makes that stand out on this failure
Makes whose cars record this failure clearly more or less often than comparable cars (same age, mileage and fuel):
- Chrysler · 4.46× comparable cars
About this defect
The wording is DVSA's, from the MOT inspection manual. A high ratio for a model reflects its MOT record, which depends on maintenance and use as well as design. For one car, its own MOT history shows whether this has come up before.
Other common brakes failures
- Brake pads: less than 1.5 mm thick · 1.89% of tests
- Rbt (sp): efficiency below requirements · 1.11% of tests
- Service brake performance: excessively binding · 0.72% of tests
- Rigid brake pipes: excessively corroded · 0.66% of tests
- Brake discs: significantly and obviously worn · 0.60% of tests
- Parking brake performance: inoperative on one side · 0.52% of tests
- Anti-lock braking system: warning lamp indicates an ABS fault · 0.41% of tests
- Service brake performance: excessively fluctuating · 0.31% of tests
Check the car you are looking at
Enter a UK registration to see that car's own MOT history and what it is likely to cost to own. Your first check is free and shows the vehicle summary and its headline ownership cost. The category-by-category breakdown is part of a paid check.
UK number plate or 17-character VIN
About this data. These are MOT test results, not a measure of mechanical reliability: a car's MOT outcome reflects its condition on the day, which depends on how it has been maintained and driven as well as how it was built. Figures cover class 4 vehicles (cars and light vans), normal tests only (retests excluded), outcomes pass, fail and pass after rectification at the station; vehicles at least 2.5 years old at test. Tests from 2023-01-01 to 2024-12-30. “Compared with similar cars” means compared with the national rate for cars of the same age, mileage band and fuel. Contains public sector information licensed under the Open Government Licence v3.0. Makes and models are matched to 73 Auto's vehicle catalogue; tests that can't be matched are left out rather than guessed. See how the MOT figures are produced.