The MOT Files

Section 1 · Brakes

1.3.1 Performance

Manual indexed

Quick answer

Sub-section 1.3.1 of the MOT inspection manual covers performance and lists 5 defects, 2 of them Dangerous. A reference like "(1.3.1 (a)(i))" on a certificate points to the matching row below. The most recorded is "Brakes imbalance across an axle such that the braking effort from any wheel is less than 50% of the maximum effort recorded from the other wheel on a steered axle", about 0.1 times per 100 failed tests.

Official wording

The defect clauses

  1. 1.3.1 (a)(i)Majorunder 0.1 per 100 fails

    Braking effort inadequate at any wheel

  2. 1.3.1 (a)(ii)Dangerousunder 0.1 per 100 fails

    Braking effort not recording at any wheel

  3. 1.3.1 (b)(i)Major

    Brakes imbalance across an axle such that the braking effort from any wheel is less than 70% of the maximum effort recorded from the other wheel on the same axle. Or in the case of testing on the road, the vehicle deviates excessively from a straight line.

    Brake binding or imbalanced across an axle explained: what it means and what puts it right

  4. 1.3.1 (b)(ii)Dangerous0.1 per 100 fails

    Brakes imbalance across an axle such that the braking effort from any wheel is less than 50% of the maximum effort recorded from the other wheel on a steered axle

    Brake binding or imbalanced across an axle explained: what it means and what puts it right

  5. 1.3.1 (c)Majorunder 0.1 per 100 fails

    A brake on any wheel grabbing severely

    Brake binding or imbalanced across an axle explained: what it means and what puts it right

Wording and categories reproduced from the DVSA inspection manual under the Open Government Licence. Frequencies are items per 100 failed class 4 tests across the DVSA anonymised MOT dataset; a clause with no figure was not recorded often enough to appear in any model’s top forty failure items. 3 of 5 clauses link to our own explanation.

Grading

What the categories mean

Dangerous
a direct and immediate risk to road safety or the environment. The vehicle fails and must not be driven until repaired, even to a garage.
Major
a defect that affects safety, the environment or other road users. The vehicle fails.
Minor
a defect with no significant effect on safety or the environment. Recorded on the certificate; the vehicle passes.

The full guide to defect grading

Section 1

Other sub-sections of brakes

All sections of the manual

Common questions

What does 1.3.1 mean on an MOT certificate?
It refers to sub-section 1.3.1 of the MOT inspection manual, "Performance", within section 1, brakes. The letter or letters after it — (a), (b)(i) and so on — identify the specific defect from the 5 listed here. 2 of them are graded Dangerous, 3 Major and 0 Minor.
Which performance defect is recorded most often?
"Brakes imbalance across an axle such that the braking effort from any wheel is less than 50% of the maximum effort recorded from the other wheel on a steered axle" (1.3.1 (b)(ii)), recorded about 0.1 times per 100 failed MOT tests nationally. We explain what it means and what puts it right.
Does a Minor defect fail the MOT?
No. a defect with no significant effect on safety or the environment. Recorded on the certificate; the vehicle passes. Major and Dangerous defects fail. A Dangerous defect also means the car must not be driven until it is repaired.