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Lotus Elise / Lotus Exige. Manual - part 21

Page 3

Lotus Service Notes

Section CI

CI.1 - GENERAL DESCRIPTION

The fully independent front suspension comprises, on each side of the car, upper and lower wishbones, a

concentric coil spring/telescopic damper unit, and a tubular anti-roll bar. A forged steel hub carrier, provides a

mounting for a the hub bearing unit to which the road wheel is attached via four spline socket bolts.

The upper and lower 'A' frame wishbones are fabricated from steel tube, the upper wishbone braced by

sheet steel gussets at its apex, and the lower wishbone braced by a tubular strut at its base. The inboard ends

of both wishbones use replaceable bonded rubber pivot bushes to provide maintenance free articulation, with

a speciﬁcation providing accurate and responsive dynamic characteristics. The outer ends of both wishbones

incorporate housings into which the upper and lower steering swivel ball joints are pressed. The upper ball

pin is secured to the forged steel, rearward facing steering arm, itself ﬁxed to the hub carrier by two M10 bolts.

The ball pin of the lower swivel joint is secured directly into a tapered hole in the bottom of the forged steel hub

carrier. The Bilstein spring/damper unit acts between the outer end of the lower wishbone and the chassis,

and is ﬁtted with the damper rod lowermost in order to minimise unsprung weight.

A forward mounted tubular steel anti-roll bar, is supported in chassis mounted rubber or hard plastic pivot

bushes and is operated via short ball jointed drop links from the lower wishbones.

CI.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

repair, or if excessive tyre wear is evident, or if steering difﬁculties are 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. This will require the vehicle to be ballasted, or tied down:

Standard Elise

Mid-laden ride height (reference height for geometry check);

- front 130 mm below front end of chassis siderail

- rear 130 mm below rear end of chassis siderail

Camber - optimum - 0.1°

- tolerance + 0.1° to - 0.3°; Max side/side 0.2°

Castor - optimum + 3.8°

- tolerance + 3.5° to + 4.1°; max. side/side: 0.35°

Alignment - optimum Zero

- tolerance 0.5 mm toe-out to 0.7 mm toe-in overall

(0.07° toe-out to 0.10° toe-in overall)

Steering axis inclination 12° nominal

Sport Elise, Exige

Mid-laden ride height (reference height for geometry check);

- all except USA prior VIN 3013 - front 130 mm below front end of chassis siderail

- rear 130 mm below rear end of chassis siderail

- USA prior VIN 3013 - front 135 mm below front end of chassis siderail

- rear 135 mm below rear end of chassis siderail

Camber - optimum - 0.3°

- tolerance - 0.1° to - 0.5°; max. side/side: 0.2°

Castor - optimum + 3.8°

- tolerance + 3.5° to + 4.1°; max. side/side: 0.35°

Alignment - optimum Zero

- tolerance 0.5 mm toe-out to 0.5 mm toe-in overall

(0.07° toe-out to 0.07° toe-in overall)

Steering axis inclination 12° nominal

Page 4

Lotus Service Notes

Section CI

Alignment

Wheel alignment refers to the parallelism of the wheels when viewed from above and is crucial to vehicle

stability, handling and tyre wear.

Alignment 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. Wheel alignment is designed to vary with both steering angle (Ackerman) and suspension travel

(bump steer) and should be measured only 'straight ahead' at the speciﬁed ride height.

Front wheel alignment is adjusted be screwing the track rods into or out of the track rod outer end ball

joints. In order to preserve the required bump steer characteristic and steering symmetry, the effective length

of each track rod must remain equal - adjust each track rod by a similar amount.

Hold the track rod end using the ﬂats provided, and slacken the locknut. Repeat for the opposite side.

Turn each track rod a similar amount. As a guide, turning both track rods by one quarter of a turn will alter

overall toe-out by approx. 2.0 mm.

When adjustment is correct, hold each track rod end and tighten the locknuts to 80 - 82 Nm (58 - 60 lbf.

ft).

When slackening or tightening the track rod end locknuts, it is important that the torque reaction is resisted

using the track rod end ﬂats, and that the ball joint itself is not allowed to be stressed.

Difference between

rim measurements

= overall toe out

FRONT

Individual

toe out

angle

c26

Steering rack gaiter

Track rod end ﬂats

Track rod end

Steering arm

Steering track rod ﬂats

Track rod end locknut

c28a

Page 5

Lotus Service Notes

Section CI

Camber Adjustment

Camber is the angle from vertical of the wheel when viewed from the front, and is said to be negative when

the wheel leans inwards at the top (positive when leaning outwards). The primary purpose of camber is to

achieve the maximum efﬁciency of the tyre under cornering loads and body roll, with the speciﬁcation closely

allied to a particular wheel/tyre combination. The camber angle changes with suspension travel, becoming

more negative on bump, and should be measured only at the speciﬁed ride height. Incorrect camber can result

in handling deﬁciencies and excessive tyre wear.

Camber adjustment is effected by adding or deleting shim plates between the steering arm (to which the

upper steering swivel joint is ﬁxed) and the hub carrier.

Shimplates are available in 1mm and 3mm thicknesses.

Reducing the shim pack thickness will increase negative camber. Adding shims will reduce negative

camber.

A 1mm shim plate will alter camber by approximately 0.25°.

In March '04 the caphead bolts securing the ball joint plinth to the hub carrier were upgraded from 8.8 to

10.9 grade, with a corresponding increase in torque from 45 to 68 Nm. Before ﬁtting these bolts, inspect

the cap head for the grade marking, apply Permabond A130 (A912E7033) to the threads, and torque

tighten to the appropriate ﬁgure.

Camber angle

c29

Vertical Wheel centreline

Camber adjustment

shimplate

Steering arm

Hub carrier

c30a

Page 6

Lotus Service Notes

Section CI

Castor Adjustment

Castor is the angle from vertical of the steering axis of the wheel when viewed from the side. Its primary

purpose is to provide a natural straight running tendency of the steered wheels with forward vehicle motion.

Castor angles have a complex interaction with other steering geometries and if unbalanced or outside of speci-

ﬁcation, can result in various stability and handling deﬁciencies.

The wishbone pivot bushes are bonded rubber type with a plastic ﬂanged outer sleeve, a plain steel in-

ner sleeve, and a plastic interleaf sleeve within the rubber bush to control the ﬂexing characteristic. The top

wishbone rear bush, identiﬁed by a blue paint mark, has no interleaf sleeve.

The top wishbone pivots are sandwiched between the walls of transverse chassis box sections, the pick

up points in which are reinforced either with machined inserts, or in the case of the foremost position, a thick

alloy plate, each being bonded to the chassis with epoxy adhesive. Spacer washers are ﬁtted ahead of and

behind each of the top wishbone pivot bushes to allow the wishbone to be displaced forwards or backwards,

with an associated change of castor angle. A rubber faced snubber washer ﬁtted against the rear face of the top

wishbone front bush prevents metal to metal contact under extreme braking forces. The spacer washers may

be re-distributed between the front and rear of each pivot bush but the snubber washer position, and the total

shim pack thickness of 4 x 1.5mm at each pivot (inc. the 1.5mm snubber washer) must remain unchanged.

FRONT

Top & bottom

steering swivels

Castor angle

c27

Top Wishbone Inboard Fixing

FRONT Front leg Rear leg

1.5mm shim 1.5mm shim

washers washers Flanged plastic

outer sleeve

Plastic Inner steel

Bonded Bonded interleaf sleeve

plate Rubber faced inserts

c32

snubber washer

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