Lotus Elise Service Notes page 91

Lotus Service Notes
Section DE
DE.1 - GENERAL DESCRIPTION
The fully independent rear suspension comprises, on each side of the car, upper and lower tubular steel
wishbones, a toe control link, and a concentric coil spring/telescopic damper unit picking up on the outboard
end of the lower wishbone. An extruded aluminium alloy hub carrier, houses a dual taper roller bearing which
supports the outboard driveshaft and a steel hub equipped with 4 wheel studs. Onto the LH hub carrier is
mounted a wheel speed sensor which operates in conjunction with a sensor ring on the outboard driveshaft, in
order to supply vehicle speed signal to the speedometer.
The inboard ends of the upper and lower wishbones use replaceable bonded rubber pivot bushes to
provide maintenance free articulation and suppression of noise and vibration. The two legs of the rearward
biased top wishbone, pick up on the chassis rear subframe, and converge outboard to a ball joint housing into
which is pressed a ball swivel joint. The ball pin of this joint locates in a forged steel plinth which is itself
secured to the hub carrier using two horizontally disposed M10 bolts. The braced, wide based, forward biased
lower wishbone, is anchored at its front inboard end to the chassis rear crossmember via a steel bracket, and
at its rear inboard end to the rear subframe. The outboard end of the wishbone houses another swivel ball joint
fixed via a forged steel plinth (similar to that used on the front suspension) to the bottom of the hub carrier by
four bolts.
The adjustable length, double ball jointed toe control link, shares a chassis anchorage with the rear of the
lower wishbone, and picks up on a rearward extension of the hub carrier.
The spring/damper unit is fitted with the damper rod lowermost to minimise unsprung weight, and acts
between the outer end of the lower wishbone and a steel clevis bracket bolted to the rear end of the chassis
main side rail.
Certain components are common with the front suspension, and include: top and bottom swivel joints,
hubs and hub bearings, and some wishbone pivot bushes.
DE.2 - GEOMETRY & ADJUSTMENTS
Provision is made for the adjustment of wheel alignment and camber. Under normal service conditions,
no periodic scheduled check of the geometry is necessary, with a full geometry check required only after
suspension repair, or if excessive tyre wear is evident, or handling deficiencies encountered. 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 half tank of fuel:
Ride height (for geometry check); - front
- rear
Alignment;
Camber;
140 mm below front end of chassis siderail
140 mm below rear end of chassis siderail
1.2 mm toe-in each side; + 0.2 mm, - 0.
(0.18° toe-in each side; + 0.03°, - 0)
Max. difference side/side; 0.2 mm (0.03°)
-1.8°; ± 0.2°. Max. difference side/side; 0.2°
Alignment
Wheel alignment refers to the parallelism of the wheels when viewed from above and is crucial to vehicle
stability, handling and tyre wear. It is measured either by the angle a wheel makes with the vehicle centre line,
or the difference in dimension between the wheel rim to wheel rim measurement at the front and rear of the
wheel at hub centre height. The wheels are said to 'toe-in' when the wheel paths converge ahead of the
vehicle, and 'toe-out' when they diverge. Rear wheel alignment should be measured only using equipment
which measures individual rear wheel alignment reletive to the car centreline. Wheel alignment is designed
to vary with suspension travel ('bump steer') and the base setting should be measured only at the specified mid
laden ride height.
It is possible to accurately measure individual wheel alignment using a pair of long straight bars or round
section elastic in conjunction with 4 axle stands or similar. Any bars used must be longer than the length of the
car, and be suitably stiff and straight.
Set up the bars or elastic on each side of the car at wheel centre height as shown an the diagram, so that
A = A, B = B and C = C.
1998 / 02
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