2002 LAND ROVER DISCOVERY Workshop Manual

FRONT SUSPENSION
60-6 DESCRIPTION AND OPERATION
Spring Data
The following table shows spring fitment applicablity.
Spring Fitment Applicability
The following table shows standard springs and uprated springs required when a front winch is fitted.
Winch Fitment Spring Applicability
Panhard rod
A Panhard rod is used to ensure that the axle remains centrally located. The Panhard rod has bushes pressed into
housings at each end which provide for the attachment to the axle and chassis. One end of the Panhard rod locates
in a fabricated bracket on the axle and is secured with a bolt and locknut. The opposite end is attached to a fabricated
bracket on the chassis and is also secured with a bolt and a locknut. The Panhard rod is shaped at one end to allow
clearance for the axle casing.
The attachment bolts for the Panhard rod are coated with a clear, dry wax which reduces friction on the bolt and allows
the correct torque to be applied to the clamping of the bushes. The bolts can be re-used, but if bolt replacement is
necessary the correct bolt with the wax coating must be used.
On models from 03 Model Year, the Panhard rod is shortened by 30 mm (1.18 in). This modification was introduced
to enhance the suspension bump steer characteristics in line with other suspension improvements introduced
simultaneously. The change to the Panhard rod also required the relocation of the attachment brackets on the axle
casing and the chassis.
Colour Code Total No. of Coils Free Length
Red/Purple 7.4 371 mm (14.6 in)
Yellow/Purple 7.4 378.4 mm (14.9 in)
Blue/Purple 7.4 365 mm (14.4 in)
Grey/Purple 7.4 387 mm (15.2 in)
Purple/Purple 7.4 373.8 mm (14.7 in)
Yellow/Orange 7.4 394.6 mm (15.5 in)
Green/Orange 7.4 382.6 mm (15 in)
Pink/Brown 7.6 405.6 mm (15.9 in)
Left Hand Drive Right Hand Drive
RH side LH side RH side LH side
Red/Purple Red/Purple Yellow/Purple Blue/Purple
Yellow/Purple Yellow/Purple Grey/Purple Purple/Purple
Grey/Purple Grey/Purple Yellow/Orange Green/Orange
Standard Spring Winch Fitted Spring
RH Side LH Side Both Sides
Red/Purple Red/Purple Grey/Purple
Yellow/Purple Blue/Purple Yellow/Orange
Yellow/Purple Yellow/Purple Yellow/Orange
Grey/Purple Purple/Purple Green/Orange
Grey/Purple Grey/Purple Green/Orange
Yellow/Orange Green/Orange Pink/Brown

FRONT SUSPENSION
DESCRIPTION AND OPERATION 60-7
Torsion/Anti-roll bar
The anti-roll bars fitted differ between ACE and non-ACE vehicles. On non-ACE vehicles a conventional 'passive' anti-
roll bar is used. On ACE vehicles an 'active' torsion bar is used. Both types are attached to the front chassis cross
member with mounting rubbers and clamp plates. The clamp plates locate in brackets on the cross member and are
each secured with a bolt. Each end of the anti-roll bar is attached to an anti-roll bar link. Each link has a spherical
bearing attached at each end. One end is attached to a bracket on the axle and secured with a locknut; a washer is
installed between the spherical bearing and the bracket. The opposite end attaches through a hole in the anti-roll bar
and is secured with a locknut. On 'active' torsion bars, the RH anti-roll bar link is attached to a long arm which in turn
is attached to the torsion bar.
Passive anti-roll bar
The passive anti-roll bar is a conventional anti-roll bar which opposes axle movement, reducing the effects of lateral
forces on the vehicle body.
With the conventional 'passive' anti-roll bar, axle movement is opposed by the anti-roll bar through links attached to
the axle casing and each end of the anti-roll bar. The anti-roll bar is manufactured from 30 mm (1.18 in) diameter
spring steel bar.
Active torsion bar

+ FRONT SUSPENSION, DESCRIPTION AND OPERATION, Description - ACE.
The 'active' torsion bar is used in conjunction with the ACE system to control body roll and directional stability giving
an improved reduction of the effects of lateral forces on the vehicle body over a conventional anti-roll bar.
The torsion bar opposes axle movement by the application of a hydraulic force to oppose the lateral forces through
links attached to the axle casing and each end of the bar. The torsion bar is made from 35 mm (1.4 in) diameter spring
steel bar. One end is fitted with an arm which is operated by a hydraulic actuator to oppose cornering forces.

FRONT SUSPENSION
60-8 DESCRIPTION AND OPERATION

FRONT SUSPENSION
DESCRIPTION AND OPERATION 60-9
DESCRIPTION AND OPERAT ION
ACE system component layout
1Anti-roll bar link
2Suction hose
3ACE/PAS reservoir
4Return pipe
5ACE pump
6Pressure pipe
7Torsion bar - front
8Actuator hose
9Actuator hose
10Actuator
11Short arm
12Long arm
13Anti-roll bar link14Isolator and bracket (2 and 4 way) 7 off
15Pressure transducer
16Valve block
17Directional control valve 2 off
18Pressure control valve
19Long arm
20Actuator
21Anti-roll bar link
22Torsion bar - rear
23Short arm
24ACE ECU
25Accelerometer - lower
26Accelerometer - upper

FRONT SUSPENSION
60-10 DESCRIPTION AND OPERATION
ACE system control diagram
1Upper accelerometer
2Lower accelerometer
3Pressure transducer
4Directional control valve
5Directional control valve
6Pressure control valve
7Instrument pack warning lamp
8Diagnostic socket9Reverse lamp switch
10SLABS ECU
11Engine Control Module (ECM)
12Ignition feed
13ACE relay
14Battery supply
15ACE ECU
M60 0589B
12
5
4
3
6
7
8
9
10
11
12
13
14
15

FRONT SUSPENSION
DESCRIPTION AND OPERATION 60-11
Description - ACE
General
The Active Cornering Enhancement (ACE) system is used to control vehicle roll angles. The following illustrations
show the difference in body roll angle between a conventional 'passive' anti-roll bar and the ACE system.
Conventional 'passive' anti-roll bar
aDirection of travel - Right hand bend
bBody roll
cAxle roll
dTyre squash
eCoil springs
fBody roll angle
gAxle roll angle

FRONT SUSPENSION
60-12 DESCRIPTION AND OPERATION
ACE system
aDirection of travel - Right hand bend
bBody roll
cAxle roll
dTyre squash
eTorsion/Anti-roll bar
fDirection of torsion/anti-roll bar twist
gCoil springs
hBody roll angle
iAxle roll angle
jReduced body roll angle with ACE system
The system is electrically and hydraulically operated with all operations controlled by an ACE ECU located behind the
glovebox in the passenger side footwell. The ACE system comprises front and rear torsion bars and actuators, two
accelerometers, ECU, hydraulic pump, valve block and a fluid reservoir.
The ACE system gives improved vehicle handling and suspension characteristics and is active for both on and off-
road driving. This is achieved by hydraulic actuators applying torque to the front and rear torsion bars in response to
lateral forces sensed by accelerometers. The ACE system prevents body roll with cornering forces of up to 0.4 g. From
0.4 g there is a progressive increase in body roll but significantly lower than a passive system. A passive system will
have a progressive increase in roll angle as soon as cornering forces are applied and will have a higher roll angle than
the ACE system for the same cornering force.
The ACE system can also detect if the vehicle is driven off-road. If off-road conditions are detected the ACE system
operation will be reduced or completely disabled at a speed of 25 mph (40 km/h) or less.

FRONT SUSPENSION
DESCRIPTION AND OPERATION 60-13
Lateral acceleration of the body is sensed by two accelerometers and signals are transmitted to the ECU. The engine
driven hydraulic pump supplies a constant hydraulic flow to the valve block. Two directional control valves are
solenoid operated by the ECU and these supply fluid to the applicable side of each actuator to apply an equal and
opposite force to the torsion bar. In operation the ACE system maintains the attitude of the vehicle body when
cornering.
The ACE system uses a semi-synthetic hydraulic fluid which is the same as the fluid used for the PAS system. The
total capacity of the ACE system is 1.62 litres (0.42 US Gallons).
CAUTION: The ACE hydraulic system is extremely sensitive to the ingress of dirt or debris. The smallest
amount could render the system unserviceable. It is imperative that the following precautions are taken.
lACE components are thoroughly cleaned externally before work commences;
lall opened pipe and module ports are capped immediately;
lall fluid is stored in and administered through clean containers.
In the event of an ECU or hydraulic failure the system will fail safe to a 'locked bars' condition. The 'locked bars'
condition will allow the torsion bars to operate in a similar manner as conventional 'passive' anti-roll bars. Prolonged
cornering forces will allow a progressive increase in roll angle due to hydraulic leakage through the actuators and
valve block. Failures will be relayed to the driver by the illumination of the ACE warning lamp in the instrument pack.
Faults are recorded by the ECU and can be retrieved using TestBook.
When the ignition switch is moved to position II, the warning lamp will illuminate for two seconds to check functionality.
The warning lamp functionality can also be checked using TestBook.
TestBook must also be used to perform a bleeding procedure after maintenance operations have been performed to
ensure that complete system bleeding is performed. Trapped air in the system can seriously reduce the system
performance.
Fluid reservoir
The moulded plastic fluid reservoir is mounted on the left hand side of the engine compartment on a bracket which is
attached to the inner wing. The reservoir is dual purpose, being divided into two separate chambers; one for the ACE
system and one for the PAS system. Each chamber has its own filler neck and cap and is identified by moulded
lettering on the reservoir adjacent to each filler.
A non-serviceable filter assembly is fitted in the base of each chamber. The filter is made from fine stainless steel
mesh which is moulded into the body of the reservoir. The filter removes particulate matter from the fluid before it is
drawn into the hydraulic pump.
Upper and lower fluid level marks are moulded onto the reservoir body. The capacity of the ACE reservoir chamber
to the upper level mark is 0.5 litre (0.13 US Gallon).