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Lotus Eleven/Elise/Exige. Manual - part 27

Page 2

Lotus Service Notes

Section DH

Rear Suspension Layout

Damper top mount

Upper ball joint

Damper

Hub carrier

Top wishbone

Rear subframe

Rear

subframe

Lower wishbone

Driveshaft

Toe control link

Wheel hub

Road spring

Lower ball joint

d20b

Page 3

Lotus Service Notes

Section DH

DH.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 linked between the outboard

end of the lower wishbone and the chassis. A forged steel hub carrier, provides a mounting for 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, with the inboard ends of both

wishbones using replaceable bonded rubber pivot bushes to provide maintenance free articulation, with a

specification providing accurate and responsive dynamic characteristics, with some suppression of noise and

vibration. The two legs of the top wishbone pick up on the chassis rear subframe, and converge outboard

and forwards 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, 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 chassis rear subframe. The two legs converge outboard and

rearwards to a ball joint housing which accommodates another swivel ball joint, the ball pin of which is secured

directly into a tapered hole in the forged steel hub carrier. The Bilstein telescopic damper with concentric coil

spring, is fitted with the damper rod lowermost to minimise unsprung weight, and acts between the outer end

of the lower wishbone and an anchorage on the steel subframe.

The adjustable length, double ball jointed, toe control link, shares a subframe anchorage with the rear pivot

of the lower wishbone, and at its outboard end, is secured directly into a tapered hole in a rearward integral

extension of the hub carrier.

The forged steel hub carrier provides a mounting for a hub bearing unit, which is secured by three 'Torx'

head bolts and incorporates a wheel speed sensor for the anti-lock brake system, engine management and

speedometer data.

DH.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/full 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);

- 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 - 1.8°

- tolerance - 1.6° to - 2.0°; max. side/side: 0.2°

Alignment; - optimum 1.2 mm (0.16°) toe-in each side

- tolerance 1.2 to 1.8 mm toe-in each side

(0.16° to 0.24° toe-in each side)

Max. difference side/side: 0.3 mm (0.04°)

Roadsport Elise, Exige (for Super Sport suspension see sub-section DH.6)

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 - 1.8°

- tolerance - 1.6° to - 2.0°; max. side/side: 0.2°

Alignment; - optimum 1.5 mm (0.20°) toe-in each side

- tolerance 1.2 to 1.8 mm toe-in each side

(0.16° to 0.24° toe-in each side)

Max. difference side/side: 0.3 mm (0.04°)

Page 4

Lotus Service Notes

Section DH

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.

Measure the distance from the bar to the rim of the wheel concerned at the front and rear of the centre line

of the wheel (D

, D

). If the front dimension, D

, is greater than the rear dimension, D

, the wheel has TOE-IN.

If the rear dimension is greater than the front dimension, the wheel has TOE-OUT. The difference between the

two measurements is the amount the wheel has toe-in or toe-out.

Wheel alignment is adjusted via the toe control link which is equipped with a left hand threaded ball joint at

the inboard end, and a right hand threaded ball joint at the outboard end. Slacken both ball joint locknuts, and

turn the link rod as necessary to increase or decrease the effective length of the link. As a guide, lengthening

the link rod by a turn of one 'flat' (one sixth of a turn) will increase toe-in by approximately 1mm.

After adjustment, tighten the two locknuts to 55 Nm taking care to ensure that the ball joint sockets are

aligned at 90° to each other to allow some free articulation.

Camber Adjustment

Camber is the angle from vertical of the wheel when viewed from the rear, 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.

Straight

edge FRONT

d21

Page 5

Lotus Service Notes

Section DH

Camber adjustment shim plates are fitted between the top wishbone ball joint plinth and the hub carrier,

and are available in 1.0 & 1.5mm thickness.

In June 2008, the shim material was upgraded and the slots deleted to enhance joint stability and com-

monise with motorsport applications. Retrofitment of the later type shims is recommended.

In all cases it is necessary to fit the plate supporting the wheel speed sensor harness.

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

camber.

A 1mm shim plate will alter camber by approximately 0.3°.

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. Retrofitment of the later type bolts is recommended.

Any attempt to adjust camber outside of Lotus specification, may result in inappropriate bolt thread en-

gagement, and endanger security.

Top wishbone

Camber adjustment

shimplate

Hub carrier

Ball joint plinth

Shimplate with wheelspeed

sensor harness bracket

d24a

Camber angle

c29

Vertical Wheel centreline

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