MAINTENANCE
INFORMATION
DATE :

JUNE 2016

SUBJECT :

MI16-14

SECTION : 16 - Suspension

SUSPENSION HEIGHT ADJUSTMENT
HEIGHT CONTROL VALVES

USING

APPLICATION
Model

All models
Model Year : From 2014
DESCRIPTION
Use this procedure when a suspension height check or adjustment must be performed.

HEIGHT CONTROL VALVES
Three height control valves automatically control air volume in the suspension air springs at three
separate locations to maintain a constant vehicle height regardless of load or load distribution.

INDEPENDENT FRONT SYSTEM HEIGHT
CONTROL VALVE
FRONT
SUSPENSION
HEIGHT
CONTROL VALVE (I-BEAM AXLE)
REAR SUSPENSION HEIGHT CONTROL
VALVE – UNDER FORE UNDERFRAME
AIR SPRINGS

MI16-14 / Page 2 / 9

The two rear suspension height control valves are mounted to the chassis and connected to the fore
air springs of the rear underframe through a control arm and link.
One front suspension valve is mounted to the chassis and connected to the front axle through a control
arm and link.
On IFS, one height control valve is located on the center of the front sway bar.
If an adjustment is required, change the position of the control arm. The control arm should be moved up
to supply air and raise vehicle height and should be moved down to release some air from air springs and
lower vehicle height. Make sure that air pressure is greater than 90 psi.
The appropriate vehicle body height is checked by measuring the clearance of all the air springs installed
on the front and rear suspension. The tag axle, by its nature, doesn’t need to be adjusted.

If an adjustment is required, begin with the rear suspension.

MI16-14 / Page 3 / 9

NORMAL RIDE HEIGHT
The normal ride height is obtained by measuring and adjusting air spring height of front and rear
suspension.

TABLE 1 – PRESCRIBED AIR SPRING HEIGHTS

FRONT
SUSPENSION
(I-BEAM AXLE)

X = 11 ¾ ± ¼ inch
(297 ± 6 mm)

2 air springs

INDEPENDENT
FRONT
SUSPENSION
(IFS)

X = 12 7/8 ± 1/4 inch
(327 ± 6 mm)

2 air springs

REAR
SUSPENSION
4 air springs

FORE AIR SPRINGS
X = 11 ½ ± 1/16 inch
(292 ± 1.5 mm)

AFT AIR SPRINGS
Y = 11 ½ ± 1/4 inch
(292 ± 6 mm)

MI16-14 / Page 4 / 9

PROCEDURE
DANGER
Park vehicle safely, apply parking brake, stop engine. Prior to working on the vehicle, set the ignition
switch to the OFF position and trip the main circuit breakers equipped with a trip button. On Commuter
type vehicles, set the battery master switch (master cut-out) to the OFF position.

REAR SUSPENSION AIR SPRINGS ADJUSTMENT
Measurement
1. Make sure that the air
system pressure is at least
90 psi.
2. Measure the drive axle air
springs clearance (all four
air springs). To do so,
measure the clearance
between the round metal
plate found above the air
spring and the other round
metal plate found under
the air spring.
3. The clearance should be
in accordance with the
value of Table 1.

Air spring height adjustment
While proceeding with one side of the
vehicle at a time, adjust the air springs
clearance with the height control valve
4. It is necessary to adjust clearance on "fill
cycle".
a) Disconnect the link. This link is
equipped with a rubber bushing that
allows easy disconnection.
b) Lower the control arm to release some
air from air springs.
c) Raise the control arm to fill the air
springs (the valve is now in “fill cycle”)
and connect the link back in place.

MI16-14 / Page 5 / 9

5. Loosen the lower mounting bolt shown.
Take note that the bolt is equipped with a
nylon insert. The bolt should be replaced
after three (3) tightenings.

INCREASING CLEARANCE
6. Rotate the valve body to increase or decrease
the clearance as shown (the mounting bracket
has a slotted hole).
7. Allow 15 minutes to the air system to settle
before measuring the resulting clearance.
Repeat previous step if necessary.
8. Tighten the lower
adjustment is done.

mounting

bolt

once

9. Repeat this procedure with the rear suspension
height control valve located on the other side of
the vehicle.
STREET SIDE

CURB SIDE

DECREASING CLEARANCE

STREET SIDE

CURB SIDE

MI16-14 / Page 6 / 9

FRONT SUSPENSION AIR SPRINGS ADJUSTMENT (I-BEAM AXLE)
Measurement
1. Make sure that the air
system pressure is at
least 90 psi.
2. Measure the front axle
air springs clearance
(two air springs). To do
so,
measure
the
clearance between the
support above the air
spring and the lower end
of the air spring (if
needed, use a small
metal ruler to reach the
lower end of the air
spring).
3. The clearance should be
in accordance with the
value of Table 1.

Air springs height adjustment
Adjust the air springs clearance with the
height control valve
4. It is necessary to adjust clearance on "fill
cycle".
a) Disconnect the link. It is equipped with
a rubber bushing that allows easy
disconnection.
b) Lower the control arm to release some
air from air springs.
c) Raise the control arm to fill the air
springs (the valve is now in “fill cycle”)
and connect the link back in place.

MI16-14 / Page 7 / 9

5. Loosen the lower mounting bolt shown.
Take note that the bolt is equipped with a nylon
insert. This bolt should be replaced after three
(3) tightenings.

6. Rotate the valve body to
increase or decrease the
clearance as shown (the
mounting bracket has a
slotted hole).

INCREASING CLEARANCE

DECREASING CLEARANCE

7. Allow 15 minutes to the air
system to settle before
measuring
the
resulting
clearance. Repeat previous
step if necessary.

8. If rotation of the control valve is not enough to
obtain the required adjustment, you can use
one of the two (2) other holes.
9. Tighten the lower
adjustment is done.

mounting

bolt

once

MI16-14 / Page 8 / 9

INDEPENDENT FRONT SUSPENSION ADJUSTMENT
Measurement
1. Make sure that the air system pressure is at
least 90 psi.
2. Measure that the air springs clearance (two air
springs). To do so, measure the clearance
between the support found above the air spring
and the lower end of the air spring (if needed,
use a metal ruler to reach the lower end of the
air spring).
3. The clearance should be in accordance with
the value of Table 1.

4. Take the measurement where indicated on the
image preferably.

PREFERRED POSITIONS
MEASURING TAPE

WHERE

TO

PLACE

THE

MI16-14 / Page 9 / 9

Air springs height adjustment
Adjust the air springs clearance with the
height control valve
5. It is necessary to adjust clearance on "fill
cycle".
a) Disconnect the link. It is equipped with
a rubber bushing that allows easy
disconnection.
b) Lower the control arm to release some
air from air springs.
c) Raise the control arm to fill the air
springs (the valve is now in “fill cycle”)
and connect the link back in place.
INCREASING CLEARANCE
6. Using a hammer, tap gently on the arm
secured to the sway bar. Even if the fasteners
are properly tightened, it will rotate around the
sway bar. Rotate the arm secured to the sway
bar to increase or decrease the clearance as
shown.
7. Allow 15 minutes to the air system to settle
then measure the new clearance. Repeat
previous step if necessary.

DECREASING CLEARANCE

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