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Car MOT Manual 2012 onwards


2.4 All Suspension Types

Information
This sub-section applies to both front and rear suspensions including any optional components fitted.

The inspections must be carried out with the vehicle over a pit or on a raised lift.
The examination of some front suspension components requires the steered wheels to be jacked up as described in Section 2.5, MOI A1 and the examination of some rear suspension components require the rear wheels to be jacked as described in Section 2.6.

A small pinch bar should be used to check for wear or play in many of the suspension components covered in this section.

Guidance for assessing corrosion and the use of the Corrosion Assessment Tool is given at
Appendix C.
The condition of the vehicle main load bearing structure not in a prescribed area is checked under Section 6.

A suspension bump stop must not be confused with rubber/synthetic suspension spring assistors.

An inappropriate repair or modification includes welded repairs or the use of excessive heat to highly stressed components see Appendix C and modifications which are likely to affect the roadworthiness of the vehicle.

Tricycle and quadricycle requirements are detailed at Section 9.2.
Method of Inspection
A. All Suspension Types

1. Check:
a. that there is enough clearance of the axle or suspension with the bump stop or chassis
b. whether any suspension unit is so weak that it does not hold the body far enough away from the road wheels.

2. Check all suspension components for inappropriate repairs or modifications.

3. Examine the vehicle structure around any subframe, spring or suspension component mounting for:

excessive corrosion i.e. within the
prescribed area, see Appendix C distortion
fractures.

Note: It is usually necessary to open the bonnet to inspect front suspension components. It may be necessary to inspect the inside of a luggage compartment or boot to effectively check prescribed areas and testable items that otherwise would not be seen.
Reason for Rejection
1.
a. Inadequate clearance of the axle or suspension with the bump stop or chassis
b. a suspension unit so weak that the body or other part of the vehicle fouls a road wheel or would do so if the vehicle was laden.

Note: a missing bump stop rubber is not a reason for rejection.

2. A suspension component with an inappropriate repair, or a modification which has seriously weakened the component.

3. 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 or supporting panelling within 30cm of any sub-frame, spring or a suspension component mounting, that is, within a prescribed area, see Appendix C.

2.4 Leaf Springs

Information
Reason for Rejection 1.a. also applies to that part of a leaf which is curled to prevent disengagement from a slipper.

Attachment of suspension units, e.g. anchor brackets, may be by bolts, nuts, rivets, welding etc. When modified spring anchor or shackle brackets are fitted, there may be more holes in the bracket than holes in the chassis. This is not a reason for rejection.
Method of Inspection
B. Leaf Springs

1. Examine each leaf spring assembly, check:
a. the condition of spring leaves
b. the condition of spring eyes
c. the lateral location of spring leaves particularly leaf splay
d. leaves for longitudinal displacement
e. the correct location of the springs to the axle for symmetry.

2. Check the security and the amount of play at the spring anchor bracket pin/bush and both pins/bushes of the spring shackle.

3. Check that:
a. anchor/shackle pins are correctly positioned and secure
b. retaining and any locking devices are present and secure.

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.

4. Check the side play at spring eyes.

Note: For normal leaf suspension, side play at the spring eye should not exceed 6mm.

5. Check condition of slipper and rebound pin. 6. Check that the spring balance beam, anchor

and shackle brackets are:
a. secure and free from signs of movement
b. free from cracks or fractures
c. complete with all nuts, bolts and rivets
d. free from excessive damage or corrosion.

Note: Damage includes damage by weld, e.g. weld blow holes or cuts which seriously weaken the component.

7. Check the security of spring and saddle to the axle.
Reason for Rejection
1.
a. A cracked or fractured leaf, or one which is permanently distorted due to damage or so deteriorated that it is seriously weakened
b. a defective spring eye c. the leaves of a multi-leaf s
pring splayed to such an extent that the action of the spring is impaired, or will foul other parts of the vehicle
d. a spring leaf longitudinally displaced
e. a spring so fitted that the axle is misaligned.

2. Excessive wear in a pin and/or bush, for example more than:
2mm for a 12mm diameter pin
3mm for a 25mm diameter pin
10% of the pin diameter for pins over 25mm diameter
deterioration of a rubber bush resulting in excessive movement.

3. A shackle, anchor or linkage pin: a. missing, not correctly positioned or
excessively loose in its bracket b. retaining or locking device, missing or
insecurely fitted.

4. Excessive side play at spring eye.

5. A slipper excessively worn, cracked, insecure or its rebound pin missing.

6. An anchor or shackle bracket: a. loose to chassis
b. cracked or fractured
c. with a nut, bolt or rivet missing
d. damaged or corroded so that it is seriously weakened.

7.
a. Evidence that a spring saddle is fractured or moving relative to the spring
b. a nut or bolt securing the spring to the axle not secure or missing.

2.4 Coil Springs

Information
Where a coil spring is incomplete, cracked or fractured at an extreme end where the spring locates on the spring mount, it should only be rejected if:

the function of the spring is impaired
following jacking, the spring ends do not locate correctly when the vehicle is lowered into the normal running position without assistance

These criteria should also be applied to springs that have been deliberately shortened or modified in order to lower the suspension.
Method of Inspection
C. Coil Springs

1. Visually examine each coil spring for general condition. In particular, look for cracks or fractures.

2. Check that both ends of the spring are correctly located.

3. Check that the spring mountings are: a. secure
b. free from cracks and fractures
c. free from excessive damage or corrosion.
Reason for Rejection
1. A coil spring:
a. incomplete, cracked or fractured
b. worn or corroded so its cross sectional area is reduced such that it is seriously weakened.

2. A coil spring not correctly located. 3. A coil spring mounting:

a. loose
b. cracked or fractured
c. seriously weakened by damage or corrosion.

2.4 Fluid-Gas-Air Suspension

Information
Care must be taken not to cause damage to body work when pushing down on the suspension.
Method of Inspection
D. Fluid/Gas/Air Suspension

1. Check suspension units and accumulators for: a. displacement
b. damage or serious deterioration
c. fouling by moving parts.

2. Check for any leak in the system.

3. Check suspension units supply pipes or interconnecting pipes for security, damage or corrosion.

4. Check the security of levelling valves.

5. At each corner of the vehicle, where practicable, push down or pull down from underneath, and note the amount of suspension movement
Reason for Rejection
1. A suspension unit or accumulator:
a. displaced or totally deflated
b. damaged or deteriorated so that it is likely to fail
c. fouled by moving parts likely to cause damage or restrict travel.

2. A leak in the system.

3. A suspension unit supply pipe or interconnecting pipe insecure, damaged or corroded so that it is seriously weakened.

4. An insecure levelling valve.

5. No suspension movement.

Note: Large vehicle suspensions can be difficult to move. Ensure there is a defect before rejection.

2.4 Torsion Bars

Information
Method of Inspection
E. Torsion Bars

1. Examine the bars for:
a. cracks and fractures
b. excessive corrosion and pitting.

2. Check the end fixings for:
a. security
b. excessive free play.

3. Examine the adjustment assemblies for security.

4. Check that the attachments of bars are:
a. secure to frame and suspension
b. free from cracks or fractures
c. free from excessive damage or corrosion.
Reason for Rejection
1. A torsion bar:

a. cracked or fractured
b. deteriorated by corrosion or pitting so that its cross sectional area is reduced and seriously weakened.

2. Insecurity or excessive play at an end fixing.

3. Adjustment assembly inadequately locked.

4. A torsion bar attachment bracket:
a. loose
b. cracked or fractured
c. seriously weakened by damage or corrosion

2.4 Bonded Suspension Units

Information
This inspection applies to bonded suspension spring units i.e. rubber cone suspension. Bonded mountings and bushes are to be inspected in accordance with sub-section 2.4G.
Method of Inspection
F. Bonded Suspension Units
1. Check that the attachments of units are:
a. secure
b. free from cracks and fractures
c. free from excessive damage or corrosion.

2. Examine the bonding of the flexible element to its associated metal fixing.

3. Check the general condition of the unit for damage and deterioration of the flexible element.
Reason for Rejection
1. A bonded unit attachment:

a. loose
b. cracked or fractured
c. seriously weakened by damage or corrosion.

2. Failure of the bonding between flexible element and the metal so that part of the unit is likely to become displaced.

3. The unit is so damaged or deteriorated that it is no longer capable of carrying out its proper function

2.4 Suspension Arms and Linkages, Sub-Frames, etc

Information
The inspections in sub-section 2.4G can be carried out in conjunction with the inspections in:
sub-section 2.5 Front Suspension, Wheel Bearings and Drive Shafts, and
sub-section 2.6 Rear Suspension and Wheel Bearings.

Some vehicles use comparatively thin gauge steel pressings for some highly stressed suspension components.

Many of these parts have hollow box sections or upfacing areas where road dirt impregnated with salt or other chemicals collects and causes serious but often very local corrosion.

Special attention should be paid to these components. See Appendix C for further guidance.
Method of Inspection
G. Suspension Arms and Linkages, Sub- Frames, etc

1. Check the following components and any attachment brackets or linkages, for presence, cracks, fractures, distortion, corrosion, wear and insecurity:
a. suspension arms wishbone etc
b. trailing arms
c. radius arms
d. tie bars/rods
e. panhard rods
f. torque/reaction arms
g. anti-roll bars
h. MacPherson struts
i. sub-frames.

2. Check the security and condition of pins/bushes/mountings and ball joints locating:
a. upper and lower suspension
arms/wishbones
b. trailing arms
c. radius arms
d. tie-bars/rods
e. panhard rods
f. torque/reaction arms
g. anti-roll bars and linkages
h. sub-frames.

3. Check that:

a. linkage pins are correctly positioned and secure
b. retaining and any locking devices are fitted and secure

4. On vehicles which have a drive shaft which forms part of the suspension, check:

a. the shaft for distortion, damage and serious corrosion
b. for excessive play in a universal joint
c. the flanges and bolts for presence and security
d. for wear in drive shaft support bearings
e. the condition and security of drive shaft coupling gaiters.
Reason for Rejection
1. A suspension component or its attachment bracket or linkage:

missing where one is fitted as standard
cracked, fractured or insecure
weld cracked
severely distorted
damaged, corroded or worn to such an extent that its strength is seriously reduced
retaining nut, bolt or rivet missing
which is adjustable and is loose in its adjustment threads, or its locking device insecure or missing.

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.

2.

Excessive play in a pin/bush or pin/bearing, for example more than:
2mm for a 12mm diameter pin
3mm for a 25mm diameter pin
10% of the diameter for pins over 25mm diameter

excessive play in ball joint
a ball joint dust cover missing or excessively damaged, deteriorated or insecure to the extent that it would no longer prevent the ingress of dirt etc.
deterioration of a rubber, synthetic bush or mounting resulting in excessive movement
deterioration of the bonding of a rubber bush/mounting resulting in excessive movement.

3. A suspension link locating pin:

a. incorrectly positioned or insecure
b. retaining or locking device missing or not properly locked.

4.
a. Distorted, damaged or excessively corroded drive shaft
b. excessive play in a universal joint
c. a universal joint:
flange incorrectly seated
flange bolt loose, missing or inadequately locked
d. a drive shaft support bearing excessively worn
e. a drive shaft coupling gaiter missing or excessively damaged, deteriorated or insecure to the extent that it would no longer prevent the ingress of dirt etc.



Reproduced from the MOT Inspection Manual by kind permission of THE VEHICLE INSPECTORATE.
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