201-03-4 Wheel and Tyre
Diagnosis and Test
Wheel and Tyre
Inspection and Verification
In order to play the maximum efficiency of the tyre,
inspection should be performed to make sure whether
the tyre pressure and the tyre are abnormal, if such as
an indicator appear, the need for dynamic balancing,
diagonal adjusting or front wheel alignment is
displayed. Inspection should be regularly performed to
make sure whether nick, scraping, wear abrasion,
bubbling, and substance embedded in the tread exist.
If a rapid rising of the tyre temperature occurs, or
when clastics are dispersed because of rough road
surface, tyre inspection should be performed
frequently.
That tyre wire indicating line is marked at the bottom
part of the tread to be serviced as a more direction
inspection of the tyre status. The exposure of the
indication line of the tyre wear indicates the need for
replacement of the tyre.
Tyre Wear Diagnosis
When indication line of the tyre wear is exposed, or
the tire shoulder is severely abrased, the tyre should be
replaced. Wear of the tyre shoulder is usually caused
by an overlarge camber angle of the radial tyre or an
overlarge toe in.
Sometimes, incorrect rear wheel toe-in setting wheels
or supporting column damage can lead to serious
“sunken” or “fan-shaped” tyre wear of the non-driving
tyre.
Seriously incorrect toe-in of the rear wheel can also
lead to other abnormal wear.
Road Test
Tyre vibration diagnosis procedure is started from
road test. Road test and face to face taking with
customers (if possible) can provides much more
information required by the vibration source.
Road test should be performed on smooth road
without fluctuation. If vibration occurs, pay attention
to and record the followings:
– Vehicle speed when vibration occurs.
– Types of vibration happed in each speed scope.
– Mechanical or audible.
– When the following conditions are changed, what
influence is affected in vibration?
– Engine torque
– Vehicle speed
– Engine rotating speed
– Vibration type - sensitivity: torque sensitivity,
vehicle speed sensitivity or sensitivity of the
engine rotating speed.
The following explanations can help identify the
source of the vibration.
Torque sensitivity
This indicates the condition can be improved and
worsened because of acceleration, deceleration,
sliding, constant speed, or exerting engine torque.
Vehicle Speed Sensitivity
This indicates that vibration happens under the same
vehicle speeds, and can not be affected by engine
torque, engine rotating speed or gear selection of the
driving axle.
Sensitivity of the Engine Rotating Speed
This indicates that vibration occurs under the identical
gears and different vehicle speeds. It can be tested by
increasing or decreasing engine rotating speed on
Neutral Gear or under stall speed experiment. If the
condition is related to engine rotating speed, the
reason may have nothing to do with the tyre.
If road test indicates tyre whimper, but shaking or
vibration is not indicated, the noise is caused by the
contacting of the tyre and the road surface.
Huge noise usually indicates a flat tire, or the noise is
created by soft thing contacting with the road surface.
The tyre whimper is mistaken for wheel shaft. The
tyre whimper will last under a certain vehicle speed
scope.
A complete road test
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