Tyres fault diagnosis table
8.8.5 Tyres fault diagnosis table
The following table lists some of the faults which
8.8.7 Steering fault diagnosis
can occur if tyres and/or the vehicle are not main-
table 1
tained correctly. Figure 8.26 shows the same.
Suggested action Symptom
Symptom
Possible faults
Possible cause/fault
Play between the Renew in most cases but play at steering rack and pinion
Excessive free
adjustment may be Wear on both outer edges
or in the steering possible of the tread
Under inflation
wheel
box
Wear in the centre of the
Ball joints or tie Renew tread all round the tyre
Over inflation
rod joints worn Column coupling Secure or renew
Wear just on one side of
loose or bushes the tread
Incorrect camber
worn
Feathering
Tracking not set correctly
As above Bald patches
Vehicle wanders, As above
Unbalanced wheels or unusual
hard to keep in Alignment
Adjust to recommended
driving technique!
a straight line
incorrect
setting
Incorrect tyre
Adjust pressures or pressure or mix
replace tyres as
8.8.6 Tyre inflation pressures
of tyre types is required
not suitable
The pressure at which the tyres should be set is
Worn wheel
Renew
determined by a number of factors such as:
bearings
● load to be carried;
Stiff steering
Wheel alignment Adjust to recommended
● number of plies;
incorrect
setting
● operating conditions;
Tyre pressures Adjust pressures ●
section of the tyre. too low
Ball joints or
Renew
Tyre pressures must be set at the values recom-
rack seizing
mended by the manufacturers. Pressure will vary
Wheel wobble Wheels out of
Balance or renew
according to the temperature of the tyre – this is
balance
190 Advanced automotive fault diagnosis
Wear in
Renew
● keep tyres in contact with the road at all times;
suspension
● work in conjunction with the tyres and seat
linkages Alignment
springs to give an acceptable ride at all speeds.
Adjust to recommended
incorrect
setting
The above list is difficult to achieve completely,
Understeer Tyre pressures
Adjust pressures
so some sort of compromise has to be reached.
or oversteer incorrect Dangerous mix
Because of this many different methods have
Replace tyres as required
of tyre types
been tried, and many are still in use. Keep these
Excessive freeplay Renew components as
four main requirements in mind and it will help
in suspension or
required
you to understand why some systems are con-
steering system
structed in different ways.
A vehicle needs a suspension system to cushion and damp out road shocks so providing comfort to
8.8.8 Steering, wheels and tyres
the passengers and preventing damage to the load
fault diagnosis
and vehicle components. A spring between the wheel and the vehicle body allows the wheel to fol-
low the road surface. The tyre plays an important role in absorbing small road shocks. It is often
Symptom Possible cause
Wandering or instability Incorrect wheel alignment
described as the primary form of suspension. The
Worn steering joints
vehicle body is supported by springs located
Wheels out of balance Wheel nuts or bolts loose
between the body and the wheel axles. Together
with the damper these components are referred to
Wheel wobble Front or rear
Wheels out of balance
as the suspension system.
Damaged or distorted
As a wheel hits a bump in the road it is moved
wheels/tyres
upwards with quite some force. An unsprung
Worn steering joints
wheel is affected only by gravity, which will try
Pulling to one side Defective tyre
to return the wheel to the road surface but most of
Excessively worn components
the energy will be transferred to the body. When a
Incorrect wheel alignment
spring is used between the wheel and the vehicle
Excessive tyre wear Incorrect wheel alignment Worn steering joints
body, most of the energy in the bouncing wheel is
Wheels out of balance
stored in the spring and not passed to the vehicle
Incorrect inflation pressures
body. The vehicle body will now only move
Driving style!
upwards through a very small distance compared
Worn dampers
to the movement of the wheel.
Excessive free play Worn track rod end or swivel joints Steering column bushes worn Steering column universal joint
8.9.2 Suspension system layouts
worn
On older types of vehicle, a beam axle was used to
Stiff steering Lack of steering gear lubrication
support two stub axles. Beam axles are now rarely
Seized track rod end joint or
used in car suspension systems, although many
suspension swivel joint Incorrect wheel alignment
commercial vehicles use them because of their
Damage to steering components
greater strength and constant ground clearance. The need for a better suspension system came from the demand for improved ride quality and