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2.3 Front Suspension & Wheel Bearings
|Information||Method of Inspection||Reason for rejection|
Many high performance machines are fitted with anti-dive front forks which lock when the brake is applied. In these cases the front wheel will need to be placed against a solid object when checking the damping.
It is important to distinguish between play in the forks and that in the wheel bearings.
Light rubbing contact between a fork leg or damper body and its shroud is acceptable.
Some smaller machines are not fitted with dampers on the front suspension.
Some fork arrangements rely on the bracing incorporated in the mudguard fixings to maintain their alignment. A mudguard insecurely fixed to the forks may therefore adversely affect the handling of the machine.
Light misting of the stanchion is
acceptable but if evidence of oil running down the fork leg is apparent the reason for rejection would apply.
Pitting of a fork stanchion is not a reason tor rejection unless damage to damper seals has occurred. It may be necessary to pull back any rubber gaiters to conduct this examination if it is possible without dismantling or damage but they must be correctly refitted.
a. Check the condition, alignment and security of the front fork assembly.
b. Check condition of suspension springs
c. Check shock absorbers for oil leakage due to seal failure
2. Check for wear in the front fork assembly by one of the following methods:
a. whilst the machine is held upright grip the front wheel firmly and attempt to turn the handlebars from side to side looking for free play in the forks;
b. on leading or trailing link type suspensions, with the wheel raised, attempt to move the swinging fork from side to side and look for play in the pivot bearings or bushes.
3. With the front wheel raised check that the wheel and its associated fixing and locking devices are present and secure and that the wheel bearings are not excessively tight or do not have excessive free play. Spin the wheel and listen for roughness in the bearings.
4. Observe the freedom of movement and the effectiveness of the damping by applying the front brake and depressing the forks several times as far as possible. (see information column).
5. Check the security of the front mudguard and look for evidence of it having been in contact with either the wheel, the tyre or any fixed part of the machine.
6. Check condition of steering and suspension with regard to corrosion. distortion and modifications.
a. a fork assembly component which is missing, loose, cracked, or excessively bent, misaligned or corroded.
b. a road spring:
(i) incomplete, cracked or fractured
(ii) worn or corroded so that its cross sectional area is reduced such that It is seriously weakened;
(iii) repaired by welding.
c. Oil leakage indicating failure of the seal.
2. Excessive free play between the sliding members of the forks or in the pivot bearings, (see information column).
a. a loose wheel spindle or securing nut(s) or locking device missing or insecure
b. Excessive roughness, tightness or free play in the wheel bearings
a. fouling between the fixed and moving parts which affects the movement of the forks, (see information column)
b. excessive stiffness in the movement of the forks
c. Forks with inadequate damping effect. (see information column)
d. an insecure fork brace
5. An insecure mudguard or one able to easily contact the wheel, tyre or any fixed point of the machine.
6. deliberate modification which significantly reduces the original strength, excessive corrosion, severe distortion, a fracture or an inadequate repair of a load bearing member or its supporting structure.
|Issue Date: July 2001|
Reproduced from the MOT Inspection Manual by kind permission of THE VEHICLE INSPECTORATE.