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Lotus Eleven/Elise/Exige. Manual - part 65

Lotus Service Notes

Section JJ

Page 13

JJ.8A - '08 MODEL YEAR UPGRADE OPTION

Introduced as an option for some '08 models, is an uprated front brake kit, comprising 4-piston front

callipers, larger diameter front discs and steel braided hoses.

Front Callipers:

At each front corner, the A.P. Racing, alloy, 4-piston front calliper is radially mounted to the front hub

carrier via an alloy adaptor bracket. Two reduced head capscrews secure the adaptor bracket to the hub
carrier, with two capscrews with washers securing the calliper to the adaptor. Two retaining pins are used to
locate the Pagid RS14 brake pads, and also secure an anti-rattle spring plate which incorporates a direction of
rotation arrow.

Torque figures: Adaptor to hub carrier; 58 Nm. Calliper to adaptor; 58 Nm. Caliper bleed screw; 17 Nm.

Front Discs:

The front discs are increased in diameter from 288mm to 308mm, and are cooled by internal curved

vanes which trail the normal direction of rotation, to result in distinct RH and LH components. Each disc is
mounted to its hub via an adaptor 'bell' from which it should not be separated under normal circumstances.
Torque of disc to bell mounting bolts; 14 Nm. Note that these discs are fitted only on the front, with standard
discs on the rear.

New thickness of the front discs is 26.00mm; minimum service thickness 25.00mm

Wheel bolts:

In order to provide sufficient clearance between the 4-piston brake callipers and all road wheel options,

the thickness of the disc mounting bell at the hub face is increased from the standard 7mm disc thickness to
11mm. This requires the use of 2mm longer wheel bolts (C117G6000F) to maintain sufficient thread engage-
ment. To reduce the possibility of incorrect fitment, both front and rear wheels are secured with the longer
bolts, with no coded security bolts fitted. Note that these bolts use the standard spline type socket heads, but
have a reduced outside diameter of the head.

Standard bolt;

B117G6000F

26mm thread length

Head outside diameter: 22mm

Long bolt;

C117G6000F

28mm thread length

Head outside diameter: 19mm

Braided hoses:

The steel braided front hoses are connected to the front callipers using a banjo fitting tightened to 25 Nm.

**************************************************************

Introduced in June 2008, at approx. ’08 M.Y. VIN serial number 1742, the ‘big brake’ kit fitted to all Exige

S models with the Performance Pack option, has been revised to a Fast Road specification. The differences
may be summarised as follows:
-

Single piece iron front brake discs replace separate iron discs and alloy mounting bells;

Bespoke single piece front callipers replace callipers with separate adaptor brackets;

Brake pad material change, front and rear;

Revised braided hoses front and rear;

Standard wheel bolts (incl. security coding) replace longer versions without security bolt;

For Cup 260 cars, a new Sport brake specification combines the Fast Road front callipers with 2-piece

front discs for marginally better disc cooling, in conjunction with Pagid pad material.

In general, the Fast Road brakes offer significant benefits over standard brakes where full vehicle per-

formance is exploited, primarily through reduced brake fade in conditions of repeated or prolonged heavy
application. Trade offs include a greater susceptibility to noise generation. The Sport brakes, have marginally
better disc cooling via the alloy mounting bells, and use the competition type Pagid pad material. Note that the
new calliper requires a new reduced thickness version of the Pagid pad (A128J0003S). Trade offs include a
greater susceptibility to noise generation, and reduced response when the brakes are cold.

Lotus Service Notes Section JJ

Page 14

The new callipers do not require the thicker disc bells formerly used to provide wheel/calliper clearance,

or the corresponding increased length wheelbolts. Consequently, a new version of the two piece disc assembly
uses the standard 8 mm flange thickness and standard wheelbolts.

Be aware that erroneously fitting a new 2-piece disc on an original ‘Big Brake’ car will result in

the road wheel fouling the brake calliper.

Comparison chart:
Feature

Standard

‘Big Brake’

Fast Road

Sport

(reference)

(discontinued)

Front calliper pistons

Piston diameter (mm)

44.45

Leading 31.75

Trailing 36.00

Calliper housing

Alloy. Bolts

Alloy. Uses

Alloy. Bolts

directly to hub

separate adaptor

directly to hub

carrier.

bracket.

carrier.

Pad material

Textar T4139

Pagid RS14B

Ferodo DS25HP

Pagid RS14B

New pad thickness

14.5

16.5

14.5

Front disc size

288 x 26

308 x 26

Front disc features

Curved internal

vanes, cross

drilled.

Common RH LH

Handed RH LH

Single piece.

Separate 11mm

Single piece.

Separate 8mm

thick alloy

mounting bell.

Wheelbolts

26mm long

28mm long

26mm long

+ coded bolt

Brake pad bedding-in

Fast Road brakes should be bedded-in according to standard handbook advice; avoid needless heavy

braking for the first 100 miles (160 km). Thereafter, the first time the brakes are used aggressively, some loss
of brake feel may be evident as the brake pads undergo a final conditioning phase. After the brakes have
cooled, full brake performance will be restored.

For cars built with Sport Brakes, and any car fitted with ‘big brakes’ using Pagid RS14B pads, an extended

bedding-in procedure is required, detailed in LSL534b (see S/B 2008/05).

Whichever brake equipment is fitted, it is vital that the brake pad material is matched at all four

wheels - do not mix front and rear pad materials.

The braided brake hoses have been revised on introduction of the Fast Road brakes to optimise hose

length and improve ‘P’ clip security. These hoses may be used as service replacement on all cars.

Lotus Service Notes

Section JJ

Page 15

JJ.9 - BRAKE MASTER CYLINDER

The tandem brake master cylinder is mounted in the front compartment and is secured to the brake servo

by two studs with M8 nuts. The cylinder uses two pistons to supply the independent front and rear brake
circuits. The cross-section below is provided for information, but the master cylinder manufacturer does not
recommend any dismantling of the unit, and supplies no replacement parts or internal components. If the
cylinder is faulty it should be renewed as a complete assembly.

To remove the unit, proceed as follows:

On Exige models, remove the front clamshell (see sub-section BR.6).

Syphon fluid from the reservoir to reduce spillage.

Release the two hoses connecting the master cylinder to the fluid reservoir, and the single hose connect-
ing to the clutch master cylinder, and plug all hoses. Disconnect the electrical cables from the reservoir
cap, cut the tie wrap and withdraw the reservoir from the mounting bracket.

Release the two brake pipes from the master cylinder, and plug the pipes and ports.

Release the two nuts securing the master cylinder to the brake servo and remove the cylinder.

Refit the master cylinder in reverse order to removal, using NEW locknuts (supplied with a new cylinder)
and tighten to the following torques:
-

Master cylinder fixing nuts; 25 Nm

Brake pipes to cylinder; 17.5 Nm

Fill the reservoir with DOT 4 non-mineral type brake fluid, and bleed the complete brake system of air
using standard vacuum assisted, pressure assisted or manual techniques.

Key to Cross-Section

Body

Passage to rear cylinder

Rear cylinder inlet port

Guide bush

Rear piston

Lip seal

Stop washer

Primary seal

Washer

10.

Spring plate

11.

Retaining screw

12.

Stop sleeve

13.

Rear piston spring

14.

Front piston

15.

Secondary seal

16.

Transfer passage

17.

Front piston stop

18.

Front piston spring

j187

Lotus Service Notes Section JJ

Page 16

JJ.10 - VACUUM SERVO UNIT

The FTE brake vacuum servo is, with the exception of the air filter and non return valve, a non-servicable

sealed unit which if found to be faulty, must be replaced as an assembly. The air filter (surrounds the input push
rod) should be replaced whenever the brake system is overhauled, and cleaned or replaced more frequently if
the vehicle is operated in dusty conditions. A vacuum non-return valve is incorporated into the vacuum hose
elbow connector in the front case of the servo unit, and a second in-line non-return valve is fitted into the supply
line close to the engine. The elbow connector valve is a push fit into a grommet in the servo shell, and is
supplied complete with the grommet.

The servo is fitted between the brake pedal and master cylinder and is of the 'suspended in vacuum' type,

wherein a flexible diaphragm divides the space inside a steel shell into two chambers. The front chamber is
connected, via a non-return valve, to the vacuum produced in the engine's inlet plenum chamber. When the
brakes are 'off', this vacuum is also applied to the rear side of the diaphragm, which is held towards the rear of
the shell by a spring. The brake pedal is connected to the brake servo control rod, which operates a control
valve before pressing against the output rod via a pliant reaction disc.

Brakes Off

In the simplified schematic diagram, with the brakes off, the diaphragm and driving piston are pushed to

the left by the main spring, and the input rod is pushed to the left by its own spring, causing the control valve to
close off the atmospheric port. Engine vacuum admitted to the right hand side of the diaphragm is also
communicated to the left side of the diaphragm, and the unit is stable.

Diaphragm

Rear chamber

Engine

vacuum

Servo control rod

Front

Brake pedal

chamber

connection

Output
rod

Air filter

Main

Diaphragm

spring

Reaction disc

j147a

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