PREVOST GKN AXLES LIMITED KIRKSTALL DIVISION, Руководство по обслуживанию

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Section 16: SUSPENSION
16-10
The appropriate vehicle body height is obtained by
measuring the clearance of all the air springs
installed on the vehicles. All air springs clearance
should be 11.5 ± 0.25" (292 ± 6 mm). Refer to
figure 12 to identify the correct location where the
measure has to be taken. At this point, it should
not be necessary to make an adjustment under
normal service conditions. However, if an adjust-
ment is required, change the position of the over-
travel lever in relation to the overtravel control
body. The lever should be moved up to raise the
height of vehicle, and down to lower it. Check that
main air pressure is at normal operating pressure
and raise the vehicle to the specified height.
Caution:
Always adjust on "fill cycle". If it is
necessary to lower vehicle height, release
sufficient air to be well below height, and ad-
just to height or fill cycle.
The normal ride height is obtained by adjusting air
spring clearance of both front and rear
suspensions as follows:
1. With the vehicle at normal operating air pres-
sure (95 - 125 psi (655 - 860 kPa)), measure
air spring clearance as illustrated in figure 12.
This clearance should be 11.5 ± 0.25" (292 ± 6
mm) for all the air springs.
FIGURE 12: TYPICAL AIR SPRING CLEARANCE
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Note:
The measure should be taken from
under the upper air spring support on sub-
frame to top of the lower air spring support on
axle (refer to fig. 12 for more details). If ad-
justment is required, begin with the drive axle.
2. Loosen the adjusting nuts on the connecting
rod of height control valve to raise or lower the
overtravel lever until the desired clearance is
reached (Fig. 13).
Note:
Allow suspension to stabilize before
taking reading.
3. When the desired height is obtained, tighten
adjusting lock nuts to 2 - 4 lbf-ft (2,5 - 5 N-m)
(Fig. 13).
8. HEIGHT CONTROL VALVE
8.1 Operation
The height control valves automatically add air to,
or release air from air springs to maintain constant
suspension height regardless of load, or load
distribution. Each valve adjusts independently
according to the following conditions:
8.1.1 Loading Position
As the load increases and lowers the vehicle
body, the overtravel lever commands the height
control valve to add air to air springs.
8.1.2 Neutral Position
When vehicle body reaches the normal ride
height, the height control valve overtravel lever
reaches the "neutral" position and keeps both the
supply and exhaust ports closed to ensure normal
ride height is maintained. This condition remains
static until the vehicle load is altered.
8.1.3 Unloading Position
As the load decreases and raises the vehicle
body, the overtravel lever commands the height
control valve to release air from air springs.