The MOT Files

Section 1 · Brakes

1.1.21 Complete braking system

Manual indexed

Quick answer

Sub-section 1.1.21 of the MOT inspection manual covers complete braking system and lists 10 defects, 3 of them Dangerous. A reference like "(1.1.21 (a)(i))" on a certificate points to the matching row below.

Official wording

The defect clauses

  1. 1.1.21 (a)(i)Major

    Other braking system (e.g. antifreeze pump, air dryer etc.) component damaged or corroded to the extent that the braking system is adversely affected

    Corrosion in a structural area explained: what it means and what puts it right

  2. 1.1.21 (a)(ii)Dangerous

    Other braking system (e.g. antifreeze pump, air dryer etc.) component damaged or corroded leaking and system functionality adversely affected

    Corrosion in a structural area explained: what it means and what puts it right

  3. 1.1.21 (b)(i)Minor

    Air or antifreeze leaking

  4. 1.1.21 (b)(ii)Major

    Air or antifreeze to the extent that braking performance is affected

  5. 1.1.21 (c)Major

    Any component insecure or inadequately mounted

  6. 1.1.21 (d)(i)Major

    Braking system component modification unsafe

  7. 1.1.21 (d)(ii)Dangerous

    Braking system component modification adversely affecting braking performance

  8. 1.1.21 (e)(i)Major

    The strength or continuity of the load bearing structure within 30cm of any braking system actuation component mounting (a prescribed area) is significantly reduced (see Appendix A)

  9. 1.1.21 (e)(ii)Dangerous

    The strength or continuity of the load bearing structure within 30cm of any braking system actuation component mounting (a prescribed area) is so weakened that the functionality of the braking system is affected

  10. 1.1.21 (f)Major

    Brake retaining or locking device ineffective or missing

    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 10 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 1.1.21 mean on an MOT certificate?
It refers to sub-section 1.1.21 of the MOT inspection manual, "Complete braking system", within section 1, brakes. The letter or letters after it — (a), (b)(i) and so on — identify the specific defect from the 10 listed here. 3 of them are graded Dangerous, 6 Major and 1 Minor.
Which complete braking system defect is recorded most often?
None of the clauses in this sub-section appears among the most-recorded failure items nationally; they are rare in practice.
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.