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Lotus Service Notes Section CK
CK.1 - GENERAL DESCRIPTION
The independent front suspension comprises, on each side of the car, upper and lower forged aluminium
wishbones, a concentric coil spring/telescopic damper unit, and a tubular anti-roll bar. A forged steel hub car-
rier, provides a mounting for the hub bearing unit to which the 5-bolt road wheel and brake disc are attached,
and also features an integral steering arm and mounting bosses for the brake caliper.
The primary, vehicle weight bearing, lower wishbone, is braced by two integral struts and features an in-
tegrated steering swivel lower ball joint, a pair of press fit bonded rubber pivot bushes, and attachment points
for a fabricated steel bracket carrying the damper lower end, and a forged steel bracket for the anti-roll bar
drop link. The upper wishbone is a simple open 'A' frame, into the apex of which the upper steering swivel ball
joint is integrated.
The inboard ends of both wishbones use replaceable bonded rubber pivot bushes for maintenance free
articulation, with a compliance profile tuned to provide the vehicle with accurate and responsive dynamic char-
acteristics. Eccentric cams incorporated at the front and rear pivot points for the lower wishbone, provide for
the adjustment of both camber and castor.
The bottom of the Bilstein monotube telescopic damper fixes to the lower wishbone via a folded steel
cradle bolted to both arms of the wishbone, with the damper top end fixing to the subframe via a substantial
alloy casting bolted to the subframe longeron. The damper uses a bonded rubber bush in the top eye for noise
suppression, and a through bolted spherical steel joint in the lower eye for optimum dynamic response, and is
orientated with the damper rod uppermost. The dual rate concentric coil spring abuts against a lower seat on
the damper body, and a rubber cushioned upper seat incorporated in the damper top mounting bracket, thus
relieving the damper top bush from vehicle weight to the benefit of noise and ride refinement. The dual rate
coil spring is mounted with the close coiled end lowermost.
A 28mm o.d. tubular steel anti-roll bar is mounted in rubber bushes to the underside of the subframe and
projects through the lower wishbone before connecting to the wishbone rear leg via a short ball jointed drop
link and a forged steel bracket.
The hub bearing unit, which is common to all four wheels, is fixed to the hub carrier by 4 bolts, and in-
corporates a double row ball bearing with the inner race of the outboard bearing formed directly in the hub
forging, and the inner race of the inboard bearing retained by a swaging operation on the hub flange. Inboard
and outboard grease seals are included in the assembly, with a vehicle speed sensor ring integrated into the
inboard seal, whose 48 pole signal is picked up by a sensor mounted in the rear of the hub carrier. This data
is used for the anti-lock brake, vehicle stability, engine management and speedometer functions.
CK.2 - GEOMETRY & ADJUSTMENTS
Provision is made for the adjustment of wheel alignment, camber and castor. Under normal service con-
ditions, no periodic scheduled check of the geometry is necessary, although a front wheel alignment check is
recommended when the front tyres are replaced. A full geometry check is required only after front suspension
component replacement, or if excessive tyre wear is evident, or if steering difficulties are manifest. Before
any measurements or adjustments are made it is essential first to set the vehicle to its ‘mid-laden’ ride height,
approximating to driver and passenger and a full tank of fuel. This will require the vehicle to be ballasted, or
pulled down on a ramp:
Type Independent. Upper and lower wishbone; co-
axial coil spring/telescopic damper; anti-roll bar.
Mid-laden ride height (2x75 kg occupants + full fuel tank) - set car to this height before measuring geometry:
- front 125 mm below front end of chassis siderail
- rear 147 mm below rear end of chassis siderail
Castor - optimum + 5.2°
- tolerance range + 5.0° to + 5.5°; max. side/side 0.3°
Camber - optimum - 0.3°
- tolerance range - 0.5° to - 0.2°; max. side/side 0.2°
Alignment - optimum Zero
- tolerance range 0.5 mm toe-out, to 0.5mm toe-in overall
Steering axis inclination 9.4° nominal
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