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3.2 Brake Systems
|Information||Method of Inspection||Reason for rejection|
|A: Mechanical Brake Components|
braking systems have levers which are designed to operate over-centre
Check for any movement at the bolts securing the back plate reaction brackets or calipers by rocking the machine backwards and forward with the brake applied.
Where there is doubt about the effect of an observed defect, the tester may at his discretion carry out a road test. (See Introduction item 5)
Fully floating brake discs are designed to have some movement. Care must be taken to not unnecessarily fail these items for security.
It may be necessary to use an assistant to operate the brake to ascertain the condition and adjustment of the mechanical components.
Mechanical Brake Components
1. Examine all the mechanical components of the brakes which can be seen without dismantling, looking particularly for:
a. badly chafed rods or levers
b. corroded, frayed or knotted cables, or crushed outer casings
c. corroded or damaged rods. levers or linkages
d. worn clevis joints
e. absence or insecurity of locking devices
f. the thickness of brake linings or pads
g. insecurity or cracking of brake drums or discs
h. any restriction to the free movement of the mechanism
i. abnormal movement of levers
indicating maladjustment or excessive wear
j. insecurity of brake back plates, reaction brackets or calipers;
k. contamination of friction surfaces by oil or grease;
l. brake disc scoring, pitting or wear;
m. brake disc run-out.
Serious reduction in strength of any component due to excessive
wear, cracking or damage (eg a brake rod reduced in diameter
by more than I/3rd of original dimension)
a. excessive chafing to rods or levers
b. a knotted, excessively corroded or badly frayed cable or a significantly damaged outer casing
c. excessive corrosion or damage to rods. levers or linkages
d. an excessively worn clevis joint
e. the absence or insecurity of locking devices (eg lock nuts. split pins etc)
(i) Brake linings or pads (other than sintered pads) less than 1.5mm thick at any point
(ii) Sintered brake pads less than 1mm thick at any point
g. An insecure or cracked brake drum or disc or securing bolts loose or missing
h. any restriction to the free movement of the system likely to impede its operation
i. abnormal movement of levers
indicating maladjustment or excessive wear. (see information column)
j. an insecure brake back plate, reaction bracket or caliper. Securing bolts loose or missing, (see information column)
k. contamination of friction surfaces by oil or grease
I. An excessively scored, excessively pitted
or excessively worn brake disc
m. Excessive run out or distortion of a brake disc.
|B: Hydraulic Components|
brake fluid level check is confined to transparent reservoirs
where these can be seen. Removal of reservoir caps is not a
A hose is to be failed for cracking or chafing only if it is severe enough to expose the hose reinforcement.
Damage to a protective sleeve may be acceptable provided the pipe or hose to which it is fitted is not damaged
It may be necessary to use an assistant
to operate the brake to ascertain the condition of the hydraulic components.
When testing motorcycles, fitted with replacement brake hoses and anodised alloy banjo fittings, give close attention to the banjo union nuts if they are not stainless Steel, as corrosion can occur resulting in the nuts failing under hydraulic pressure. If the nuts are not stainless, advise the presenter even if the nuts appear sound at the time of the test, as all alloy fittings are not recommended for road use.
Examine where practical hydraulic reservoirs and cylinders for:
a. security of mountings
b. excessive damage or corrosion
c. presence of reservoir cap
d. fluid level
2. Examine all visible brake pipes for
a. chafing, corrosion, damage
b. security c. fouling and leaks
3. Examine all flexible hoses for a. chafing, twisting or kinking
b. deterioration, stretching, fouling
4. With each hydraulic system held under pressure, check for fluid leakage and hose/s bulging.
5. Hold each hydraulic system under pressure and check for pedal and lever creep.
6. On machines with finked type braking systems check all master cylinder and caliper pivot points for freedom of movement and wear.
A reservoir or cylinder:
a. insecurely mounted
b. severely damaged or corroded
c. with reservoir cap missing
d. with dangerously low fluid level
e. leaking hydraulic fluid
2. A brake pipe which is
a- Excessively chafed, corroded or damaged
b. rigid pipes inadequately supported
c. pipes or hoses likely to be fouled or trapped by moving parts
a hose which is excessively a. chafed twisted or kinked
b. deteriorated, fouling or can be stretched by steering or suspension movement
4. a hose which bulges or any part of the system leaking fluid under pressure.
5. a pedal or lever that creeps under pressure
6. an excessively worn or seized master cylinder or caliper pivot.
|Issue Date: July 2001|
Reproduced from the MOT Inspection Manual by kind permission of THE VEHICLE INSPECTORATE.