Car MOT Manual 2012 onwards
3.5 Mechanical Brake Components
InformationIt is acceptable to fit cable expanders to reduce maladjustment.
A visual and physical check must be carried out on all mechanical components that are visible and accessible.
Brake slack adjusters are usually only found on large vehicles with air braking systems.
Method of Inspection1. Check the mechanical brake components for:
a. chafed rods or levers
b. frayed or knotted cables
c. free rotation of clevis joints between cables and levers this includes cable linkages between brake pedals and remote mounted servos
d. security of cables, rods and clevis joints
e. a corroded or damaged rod, lever or linkage. Wear in eyes of relay levers, clevis joints, stationary pins or pivots
f. abnormal movement of levers, indicating maladjustment or excessive wear
g. security and excessive wear of brake linings/pads
h. contamination of brake discs and drums by leaking brake fluid, oil or grease
i. the condition and security of brake drums and discs
j. presence and security of brake back plates, wheel cylinders and calipers
k. restriction of free movement
l. presence and security of locking devices
Note: It is not always possible to determine the presence and effectiveness of certain types of locking devices e.g. locking fluid or nyloc nuts. m. condition and operation of brake slack adjusters
n. any inappropriate repair or modification.
Reason for Rejection1.
a. A brake rod or lever reduced in thickness by more than 1/3rd
b. a brake cable:
• knotted or,
• with wires broken so that the cable is weakened significantly
c. seizure of clevis joint pivots which causes strain or wear to cables to an extent likely to lead to premature failure of the cable
d. a cable, rod or clevis joint insecure
e. serious weakening of any part due to excessive wear, damage or corrosion
f. abnormal movement of levers indicating maladjustment or excessive wear
g. a brake lining or pad insecure or less than 1.5 mm thick at any point
h. a brake disc or drum contaminated by brake fluid, oil or grease i. a brake disc or drum in su
ch a condition that it is seriously weakened or insecure
j. a brake back plate, wheel cylinder or caliper securing device loose, missing or excessively deteriorated
k. restricted free movement of brake components
l. a locking device missing or insecure
m. a brake slack adjuster obviously defective or incorrectly installed
n. a mechanical brake component inappropriately repaired or modified.