MOT defect file
Parking brake efficiency too low
Last updated
Quick answer
The handbrake did not produce enough braking force on the rollers. Most cars must reach 16% efficiency, and a parking brake that falls short will not reliably hold the vehicle on a hill.
- Typical cost
- £120–£420
- DIY viability
- Garage job
What you might notice
- The car creeps forward on a slope with the handbrake fully applied
- Needing the last click or two of lever travel to hold at all, where it used to hold halfway
- A handbrake that holds on a flat surface but not on a gradient, which is the usual way owners find out
- Nothing obvious at all if you always park on the level and leave it in gear — plenty of people fail this without ever suspecting it
What causes it
- Rear brake shoes or pads worn thin, or glazed and polished from years of light use
- One side of the mechanism seized, so the whole effort goes through a single wheel and half the possible force is missing
- A stretched cable or an out-of-adjustment mechanism, so the shoes never reach the drum properly
- Oil or brake fluid contamination on the rear friction material, which cuts grip dramatically without looking dramatic
Advisory or failure?
For most cars the parking brake must achieve at least 16% efficiency, and anything below that is a major defect and a failure. Where the parking brake achieves almost nothing at all, the tester can grade it dangerous rather than major. It is also assessed for imbalance and for whether it operates on both wheels of the axle, so a brake that reaches 16% through one wheel alone can still be recorded as defective. One point that surprises owners: the parking brake is tested entirely on its own, so a car with excellent service brakes can still fail on this item alone.
Can you fix it yourself?
Garage job
The difficulty is not the repair but the diagnosis, because low parking brake efficiency is a symptom with at least four common causes and you cannot tell them apart from the driver's seat. A garage puts the car on a rolling road brake tester and reads the force from each rear wheel separately, which immediately distinguishes a stretched cable from a seized mechanism from contaminated linings. Trying to fix it by winding on cable tension is the classic mistake: it may pass on the day, but it loads one shoe, wears it out quickly and leaves the underlying fault in place. Once the cause is known, some of the individual repairs — a cable, a set of shoes — are within a competent DIY reach, but the measurement is not.
What it costs
A brake test to establish the cause is £30 to £60, and many garages fold it into the repair. From there the fix drives the price: adjustment is £30 to £60, a cable £90 to £200 fitted, rear shoes and drums £250 to £320, and a seized rear calliper with an integral parking brake mechanism £300 to £420. The top of the band applies when the diagnosis turns up more than one cause, which is common on an older car where the cable, the adjusters and the linings have all deteriorated together. Cars with an electronic parking brake sit higher again because of the diagnostic time involved.
What happens if you ignore it
The immediate risk is a parked car that moves. On a hill that is a genuine hazard to other people, and leaving a vehicle without an effective parking brake applied is an offence in its own right, separate from the MOT. There is a second, less obvious consequence: because the parking brake usually shares the rear brakes with the service brake, a parking brake that cannot reach 16% is telling you the rear brakes are worn, contaminated or seized, which means your ordinary braking is also compromised and the balance front to rear is wrong. Left long enough, what would have been an adjustment and a set of shoes becomes drums, callipers and cables together.
Common questions
- What handbrake efficiency do you need to pass an MOT?
- For most cars the parking brake must achieve at least 16% efficiency, and anything below that is a major defect. Where it produces almost nothing at all, the tester can grade it dangerous. It is also assessed for imbalance and for whether it works on both wheels, so reaching 16% through one wheel alone can still be recorded as defective.
- Can a car fail its MOT on the handbrake alone?
- Yes, and it catches plenty of owners out. The parking brake is tested entirely separately from the footbrake, so a car with excellent service brakes can still fail on this item on its own. Most people never suspect it, because a handbrake that holds on the flat can be well short of what a gradient demands.
- Why is my handbrake weak when the footbrake feels fine?
- Because it depends on a small part of the rear brakes and a mechanical linkage, both of which suffer from lack of use rather than mileage. Rear shoes or pads glazed by years of light braking, one side of the mechanism seized, a stretched cable or contaminated friction material will all cut parking brake force while barely affecting the footbrake.
- Can I just tighten the handbrake cable to get through the MOT?
- It might pass on the day, and it is the classic mistake. Winding on tension masks worn linings or a seized adjuster, puts the whole load through one shoe, wears it out quickly and leaves the real fault in place. A rolling road test that reads each rear wheel separately is what actually tells the causes apart.
- How much does it cost to fix a handbrake that fails on efficiency?
- A brake test to establish the cause is £30 to £60, and many garages fold it into the repair. From there, adjustment is £30 to £60, a cable £90 to £200 fitted, rear shoes and drums £250 to £320, and a seized rear calliper with an integral parking brake £300 to £420. Older cars often have more than one cause at once.
Cars this happens to most
Of every model with at least 2,000 tests in the DVSA data, these record parking brake efficiency too low on the largest share of their MOTs. Across all of them the typical rate is 1.8% of tests.
710 times in 3,313 tests
980 times in 4,861 tests
502 times in 2,923 tests
- Toyota MR216%
1,590 times in 9,713 tests
562 times in 3,787 tests
1,091 times in 8,383 tests
666 times in 5,339 tests
349 times in 2,812 tests
A high rate here is a property of the fleet as much as the car: these models skew old, and almost everything fails more with age. It is a reason to check the item on a used example, not proof the model is badly built. Models with fewer than 2,000 tests are left out because a rate drawn from a few hundred cars moves too much to rank.
Warning lights behind this
This defect is what a tester writes down. What you see from the driver’s seat is a symbol, and it is worth checking which one, because manufacturers reuse the same shape for more than one system.
This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.
Has this been recorded on your car?
Check the full MOT history for any UK registration.