Wiring diagram – Late V8’s 412 to Beaufort

Thank you to Jeff Marsh for providing the following wiring diagrams:

Click here to download (TYPE, 8.85MB)

Click here to download (TYPE, 7.91MB)

Click here to download (TYPE, 8.81MB)

Click here to download (TYPE, 8.01MB)

Click here to download (TYPE, 3.95MB)




Wheel Bearings


Manufacturers do not want to make replacement from other sources that easy, regularly mixing two standard bearings into one assembly, although I doubt that Bristols went this far.

Take off one complete set of bearings (2 sets of bearings per hub; the inner bearing is usually larger than the outer; both will be tapered roller bearings) and find yourself a local  machine tool service company.   Take your bearings in and they will measure them while you wait (about 5 minutes).  There are 3 grades of bearings used classed  A, B and C.  The tolerances in manufacture are, of course, extremely tight so they employ an automatic grading system – A being the best and that’s what you want.  C are the poorest and probably go into washing machines and the like.   I think the classification system may have changed possibly 1 – 3.  If the numbers on the bearings are visible you should be able to quote these to any bearing company and avoid the need to go to a machine tool service company.

Valid at time of writing in October 2016:

There are a number of good bearing suppliers eg Seager Bearings, Kings Heath, Birmingham (0121 444 5391) who will supply at trade prices.

Door boot seals & draught excluder

Please find contact details of the Furflex/draught excluder supplier:-

William Marston Ltd
70 Fazeley Street
B5 5RD

Tel: 0044 121 643 0852 or 0044 121 643 0372

email: info@williammarstonltd.co.uk
website: http://www.williammarstonltd.co.uk

The boot seals can possibly be obtained from:-

Phoenix Supplies
Unit c1a Langlands Business Park
Devon EX15 3D4
Contacts: Nigel or Kaye Coles

Tel: 0044 1884 849294

email: phoenixsupplies@hotmail.com
website: http://www.phoenixclassictrim.com

or –

Woolies (I & C Woolstenholmes Ltd)
Whitley Way
Northfields Industrial Estate
Market Deeping

Tel: 01778 347347

email@ info@woolies-trim.co.uk
website: http://www.woolies-trim.co.uk

Both of these companies carry a large range of extruded sections and just may be able to help with boot and door sections.

Classic Car Keys

This company can supply any of the Bristol key patterns, either as a duplicate or to a code.  The code can be found on the barrel of the lock.  This does entail removing the barrel from the lock.

Wilco Direct

Unit D1/D2, Pinetrees Road, Pinetrees Business Park, Norwich, Norfolk, NR7 9BB


Classic car key page at time of writing

Email address

V8 ignition switch



 Recently, it was reported on various Bristol Forums, that owners of at least one model, the 411, were experiencing Ignition Switch failures. Initially, these parts were replaced, only to have a similar issue a short time later. Understandably, owners were less than pleased after the replacement failed again, and this article attempts to illustrate the reasons why, and to recommend a remedy, that is well proven.


Having been employed at a leading company in the Motor Industry in Coventry for over thirty years, reliability testing was a major part of my engineering activities. This involved the logging of prototype vehicle test data to prove out the various electrical components. The information thus gathered then gave an indication of the vehicle lifetime expectancy of each item, and this could be used for warranty investigations later on, if required.

Major electrical loads were monitored during the tests, including air conditioning, cooling fans, external lighting, heated rear screen, heated front screen, electric windows, seat heaters, and in-car entertainment ( radio/ amplifiers, TV etc.). Data from component suppliers was also analysed, to ensure that, for example, the ignition switch, was being operated under electrical load conditions appropriate to the supply company’s recommendations. Also, back emf (the spark that appears across the contacts) at switch-off, did not exceed the limit outlined in DIN57-879. This Europe-wide specification relates to radio frequency interference by induced transients from inductors, ie, motors and solenoids, and requires sufficient suppression to be fitted to eliminate the effect.

The table below, illustrates some of the issues involved, with measurements taken before and after suppression components had been added, clearly demonstrating an improvement and compliance with the DIN regulation, (36V max @ 1mS duration).



Transient  at switch-off  before suppression

Transient  at switch-off  with suppression

Seat motor

– 232v @ 1 mS duration

– 31v @ 0.5 mS duration

Cooling fan

-183v @  0.5 mS duration

– 32v @ 0.4 mS duration

Air Con fan (interior)

– 247v @ 0.4 mS duration

– 34v @ 0.35mS duration

mS = mille-second

Over time, the energy generated across relay contacts at switch-off from unsuppressed components, will burn away the contact faces, and lead to switch/relay failure. Adding the suppression improved the reliability of the circuit components, and thus reduced failures to a minimum. Good for customer satisfaction.

A similar approach was taken with external lighting, where values obtained for the switch-on current of filament lamps were also measured. These included sidelights, head and fog lamps. The following table gives some of the results that could be applied to the wiring systems of Bristol cars:



In-rush current at switch     ON – AMPS

Illuminated/rated current – AMPS

H4 – Dip beam 55 watts

45 peak @ 10mS

4.58 @12v nominal

H4 – Main beam 60 watts

50 peak @  10mS

5.00 @ 12v nominal

Indicator 21 watts

17.5 peak @  10mS

1.75 @ 12v nominal

Sidelight 5 watts

  4.1 peak @ 10mS

0.41 @ 12v nominal

Also, the value of current that could be reliably passed by the ignition key switch was determined to be approximately 20 amperes. To switch more than this limit, several load relays were introduced to power up the various vehicle systems controlled by “Ignition ON “. These included headlamp flash, headlamps, fog lamps, heated rear/front screens, air conditioning, seat motors, In-Car entertainment systems, and fuel injection/engine management.  The circuitry included fusing for each relay controlled load, and reduced the amount of current directly switched by the ignition key. This reduced the probability of electrical failure of the ignition switch by a considerable margin. Also, the impact of Vehicle Construction and Use Regulations, and Federal (USA) NHTSA legislation, led to circuit evaluation for compliance. For example, all cigar lighters at that time, were required to be switched by the ignition key, and driving/ fog lamps if fitted, were to be switched in pairs, and not individually. These legislative requirements were subsequently incorporated into the circuitry.


Ignition switch

This is sourced from a Range Rover application amongst others for the 411 model, but the following set of conditions leading to failure, would apply to most other vehicles produced by Bristol with similar wiring/circuitry. Excessive loading leading to early contact failure, especially with the cigar lighter sockets being used to power up various items such as games and DVD players for the rear seat passengers, combined with heated rear window current, plus the usual driving aids such as demisters, windscreen wipers, and cooling fans, will cause the ignition switch contacts to fail after a short time. This is exactly what happened previously.

The following re-routing of the circuits is applicable to most of the later cars from 408 onwards, as the wiring is terminated in the right hand wing locker, and the circuit colours can easily be identified and modified. Of course, when designing circuitry for a new vehicle, one relay would supply two or three additional loads, however, when modifying existing wiring, individual load relays are easier to include without a major strip out of the wiring looms.

See Appendix 1 for the wire colour designations, these follow the old Lucas wiring colours, but for some applications, owners should consult the vehicle handbook/workshop manual for specifics.

The following Key-In Ignition ON loads supplied directly from the ignition switch should be removed, and powered up via an additional relay

1)     Heated rear window;

2)     Electric windows;

3)     Air conditioning(where fitted);

4)     Cooling fans

5)     Cigar lighters (where applicable)


This then leaves the ignition circuits, wiper motor plus the radio, (without external/ additional amplifiers) at about 12 – 14 amps, that is well within the load capability of the key switch.  .




This is a function of the indicator switch stalk. However, the contact rating is about 10 amps on my car (a 408 MkII), and looking at the current in-rush values for the main beam filaments in Table B, it can be seen that flashing four headlights results in a combined in-rush current of 190 amps for 10mS duration, after which the steady current is 19 amps, almost twice the rating of the switch. Also, the voltage at the lamps is reduced, and hence the light output, because the cross sectional area of the wiring to the flasher switch is too small. This is another circuit that requires a relay to switch the filament load.


The supply to this circuit should be removed from the ignition switch as previously discussed, and the following additional modification ought to be carried out. The cooling fan circuit utilises a thermal switch manufactured by Otter, situated in the radiator header tank. This switch controls the fan relay, and will fail if the relay coil is not suppressed. The back emf (spark), generated at switch off on an unsuppressed relay, is typically as high as 92 volts for 2mS duration. This appears across the thermal switch contacts that open relatively slowly when compared to similar relay contacts. The slow opening speed draws an arc across the air gap as the contacts move apart, and erodes the mating faces. Eventually, with carbon build up, the contacts when made will be of a high resistance, and the relay will fail to operate because of it. Therefore, a 0.1 microfarad capacitor should be wired in parallel with the relay windings to eliminate the issue. These suppressors are readily available from accessory suppliers



The only modifications that I have carried out to my own vehicle, a 408 MkII, are the suppressor modification on the cooling fan relay, a headlamp flash relay with a fuse in the power feed, fog lamps paired up with their own relay, and changed the starter relay for a plug-in type, as the original had burnt contacts. Additional fuses have been fitted in the headlamp circuit, the front fog lamp pair, and the rear fog lamp pair. As my vehicle is without a heated rear screen, the cooling fans remain wired through the key-switch as is, the load current is about 10 amperes. All of the applications discussed previously, can use relays sourced from Jaguar parts suppliers, See Appendix 2.( NB The cigar lighters on my vehicle are powered directly via a fuse from the battery, and therefore are not controlled by Ign-ON.)

When attempting to modify the circuitry, it is recommended that the cheaper alloy type of lucar spade terminations are not used, as electrolytic corrosion will ensue in damp conditions, owing to two dissimilar metals being brought together in the cable crimp, ie copper and aluminium. Always use either brass or tinned brass for these crimped terminations. Again, these are available from companies that advertise in classic car publications and the Internet.

Regarding the 411 ignition switch failures. These occur because the original circuit design did not take into account the maximum current that could be reliably switched by the contacts. Having the air conditioning on, with the wipers and demisters running, plus the heated rear screen and other accessories being powered from the cigar lighter socket(s), would probably produce a back emf at switch-off, that would easily erode the contact faces of the switch element in a relatively short time. Changing the switch again is only a short term solution, and the only effective method to eliminate premature failure, is to apply the circuit changes discussed in this article.


APPENDIX 1 – Wire colours

Many British designed vehicles use colour coded cables to assist in identifying the various circuits in use. This is an extract from BS-AU7a 1983 Colour Code for Vehicle Wiring, from the British Standards Institution, 2 Park St., London W1A 2BS.

(Note that these colour codes may not apply directly to older cars. For example, the wipers on cars up to 1980 (at least) are not on a separate fuse circuit, so they are not orange, but green. Check the schematic for your car to be certain.)


Black All earth connections
Black Purple Temperature switch to warning light
Black Green Relay to radiator fan motor
Black White Brake fluid level warning light to switch and handbrake switch, or radio to speakers
Black Orange Radiator fan motor to thermal switch


Blue Lighting switch (head) to dip switch
Blue Brown Headlamp relay to headlamp fuse
Blue Red Dip switch to headlamp dip beam fuse
Fuse to right-hand dip headlamp
Blue Light green Headlamp wiper motor to headlamp wash pump motor
Blue White a) Dip switch to headlamp main beam fuse
b)Headlamp flasher to main beam fuse
c)Dip switch main beam warning light
d)Dip switch to long-range driving light switch
Blue Yellow Long-range driving light switch to lamp
Blue Black Fuse to right-hand main headlamp
Blue Pink Fuse to left-hand dip headlamp
Blue Slate Headlamp main beam fuse to left-hand headlamp or inboard headlamps when independently fused
Blue Orange Fuse to right-hand dip headlamp


Brown Main battery lead
Brow Blue Control box (compensated voltage control only) to ignition switch and lighting switch (feed)
Brown Red Compression ignition starting aid to switch
Main battery feed to double pole ignition switch
Brown Purple Alternator regulator feed
Brown Green Dynamo ‘F’ to control box ‘F’
Brown White Ammeter to control box
Ammeter to main alternator terminal
Brown Yellow Alternator to ‘no charge’ warning light
Brown Black Alternator battery sensing lead
Brown Slate Starter relay contact to starter solenoid


Green Accessories fused via ignition switch
Green Brown Switch to reverse lamp
Green Red Direction indicator switch to left-hand flasher lamps
Green Purple Stop lamp switch to stop lamps, or stop lamp switch to lamp failure unit
Green Light green Hazard flasher unit to hazard pilot lamp or lamp failure unit to stop lamp bulbs
Green White Direction indicator switch to right hand flasher lamps
Green Yellow Heater motor to switch single speed (or to ‘slow’ on tow- or three-speed motor)
Green Black Fuel gauge to fuel tank unit or changeover switch or voltage stabilizer to tank units
Green Pink Fuse to flasher unit
Green Slate a)Heater motor to switch (‘fast’ on two- or three-speed motor)
b)Coolant level unit to warning light
Green Orange Low fuel level switch to warning light


Light green Instrument voltage stabilizer to instruments
Light green Brown Flasher switch to flasher unit
Light green Blue a)Flasher switch to left-hand flasher warning light
b)Coolant level sensor to control unit
c)Test switch to coolant level control unit
Light green Purple Flasher unit to flasher warning light
Light green Green Start inhibitor relay to change speed switch; or switch to heater blower motor second speed on three-speed unit
Light green Yellow Flasher switch to right-hand warning light
Light green Black Front screen jet switch to screen jet motor


Orange Wiper circuits fused via ignition switch
Orange Black Switch to front screen wiper motor parking circuit
Orange White Timer or intermittent unit to motor parking circuit
Pink white Ballast terminal to ignition distributor


Purple Accessories fed direct from battery via fuse
Purple Brown Horn fuse to horn relay when horn is fused separately
Purple Blue Fuse to heated rear window relay or switch and warning light
Purple Red Switches to map light, under bonnet light, glove box light and boot lamp when fed direct from battery fuse
Purple Green Fuse to hazard flasher
Purple Light green Fuse to relay for screen demist
Purple White Interior lights to switch (subsidiary circuit door safety lights to switch)
Purple Yellow Horn to horn relay
Purple Black Horn to horn relay to horn push
Purple Pink Rear heated window to switch or relay
Red Main feed to all circuits mastered by side lamp switch
Red Brown Rear fog guard switch to lamps
Red Blue Front fog lamp fuse to fog lamp switch
Red Purple Switches to map light, under bonnet light, glove box light and boot lamp when side lamp circuit fed
Red White a)Side lamp fuse to right-hand side and rear lamps
b)Side lamp fuse to panel light rheostat
c)Fuse to panel light switch or rheostat
Red Yellow Fog lamp switch to fog lamp or front fog fuse to fog lamps
Red Black Left-hand, side lamp fuse to side and tail lamps and number plate illumination
Red Pink Side lamp fuse to lighting relay
Red Orange Fuse box to rear fog guard switch
Slate Window lift main lead
White Ignition switch or starter solenoid to ballast resistor
White Brown Oil pressure switch to warning light or gauge, or starter relay to oil pressure switch
White Blue Choke switch to choke solenoid (un-fused) and/or choke to switch to warning light, or electronic ignition distributor to drive resistor
White Red Starter switch to starter solenoid or inhibitor switch or starter relay or ignition (start position) to bulb failure unit
White Light green Start switch to starter interlock or oil pressure switch to fuel pump or start inhibitor switch to starter relay or solenoid
White Yellow Ballast resistor to coil or starter solenoid to coil
White Pink Ignition switch to radio fuse
White Slate Current tachometer to ignition coil
White Orange Hazard warning lead to switch
Yellow a)Overdrive
b)Door locks
c)Gear selector switch to start


V8 Braking systems

 407-410 Brake data

Master Cylinder Repair Kit
407 – 88840 KL 71410
408 – 88840 KL 71410
409 (All) – 88840 KL 71410
410 (All) – 88840 KL 71410

Other Vehicles that use the 88840 Master Cylinder

  • Austin Commercial LD1, LD01 (1 Ton), LD2, LD02 (1.5 Ton) up to chassis 16120
  • B.M.C. Commercial 1 Ton FC LDM20 1962 – 1967 & 260LD 1968-onwards B.M.C. Prime Movers FD.2 Loader 2WL Loader
  • British Jeffrey Diamond – Wakefield Road Grader 603 1966 on
  • Conveyancer E20-20 / 6-20 (Some) / E20-20 1955 Mk XXV / E2-24, G4-24
    E3-20, D4-24 / E4-15, G4-15 / E4-20, G5-16 / E22 RC Truck 1965-onwards / MkII, MkIv, MkVI
  • Coventry Climax IGY / Electrical IndustrialTractor Model-TE 1965-onwards Universal Major Trucks Models MSD, MSDA, MSP, MSPA, MCD, MCDS, MCP, MCPA, MED, MEDA, MEP, MEPA,
  • Universal Major Electric Fork Lift Truck MSE, MCE, & MEE 1963-onwards / Research Truck RT.812 / TLJ / UTF
  • Universal Petrol & DieselFork Lift Truck IGPT, IGPTA Series II, IGDT, IGDTA Series II / IGEUS
  • Universal Major Electric Fork Lift IGET / Series I & II, IGETA Series II / Bulkloader (Mechanical Shovel)
  • Halifax Tool Company 26Hr Battery Electric Tractor 1967-onwards
  • Lister Tractor 50cwt 4’7.5″ W.B.
  • Morris Commercial LLD1, LD01 (1 ton), LD2, LD02 (1.5 Ton) up to chassis 16120, LD4 LDOA Petrol RHD & LHD)
  • Morrison Electricars E type25 cwt. BE, E25 cwt. / BEV (Morrison BM60 & BM60 MkII 1928-onwards
  • Trojan 15cwt, Van 1950-onwards / Electrojan Battery Electric 20cwt Van 1952 onwards / Trojan -Carrimore Articulated 1952 onwards Trojan-Tasker / Articulated 1954 onwards.
  • Yale & Towne K51-60 Fork Lift Truck Model Yale Tractor Shovel (Throttle Control).


Servo Unit Repair Kits
407 = 4257-567 (Bristol Cars Only) Major Repair Kit SSB.72573
Piston Packing Kit KL 72523
Air Control Valve Kit 72525
408 (To Chassis 7200) = 4257-567 Major Repair Kit SSB.1034
Air Control Valve Kit SSB.1011
408 (From Chassis 7201) = 4258-445 Major Repair Kit SSB.1034
Air Control Valve Kit SSB.1011
409 (All) = 4258-445 Major Repair Kit SSB.1034
Air Control Valve Kit SSB.1011
410 (All) = 4258-445 Major Repair Kit SSB.1034
Air Control Valve Kit SSB.1011


  • Major Repair Kit – Includes the items that should be replaced whenever the unit requires servicing, regardless of cause.
  • Piston Packing Unit – Includes parts which must be used, in addition to the parts included in the major repair kit, if the leather Piston Packing needs to be replaced.
  • Air Control Valve Kit – Consists of a sub-assembly of the end cover, valve and air pipe, to be fitted as a complete unit, each time a valve requires replacement.

Other Vehicles that use the 4258-445 Servo Unit

  • A110 Westminster MKII 1964-onwards / A110 Westminster MKII Provincial Police Car 1967-on.
  • Daimler Majestic Major 450/1 Limousine from chassis 136573.
  • Vanden Plas Princess 4 Litre R 3909cc 1964-onwards.
  • Wolseley 6/110 MKII 1964-onwards / Wolseley 6/110 Provincial Police Car 1967-onwards.

Click here to download (TYPE, 692KB)

Front Exchange Caliper Models Dates
Lucas SP2511 411 – All Models 1969-75
Lucas SP2511 412 S2, 603 E, 603 S2 1976-82


Make Also Used On Dates
SP2511 Jaguar (Daimler) Daimler Double Six – 5.3, 5.3 HE 1972-09/73
SP2511 Jaguar E Type – 4.2, 5.3, V12 1968-74
SP2511 Jaguar XJ12 5.3 1972-09/73
SP2511 Jensen Interceptor MKIII 7.2 1971-76
SP2511 Reliant Scimitar 3.0 GTE 1968-72
SP2511 Rover Group P6 3500 1968-76


Rear Exchange Caliper Models Dates
Lucas SP2524 411 – All Models 1969-75
Lucas SP2524 412 S2, 603 E, 603 S2 1976-82




Make Also Used On Dates
AC 3000 ME – All Models 1974-86
AC 428 – All Models 1969-74
Aston Martin DB6 – All Models 1969-71
Aston Martin DBS 6 – All Models 1971-73
Aston Martin DBS V8 – All Models 1970-72
Aston Martin V8, V8 Volante – All Models 1972-77
Jensen Interceptor MKIII 7.2 1971-76

Rear Hose Used On Dates
PCH100 411 1969-75
PCH100 412 Conv. S2 1975-77
PCH100 412 S, 603 E, 603 S2 1976-82
PCH100 603 E, S, S2 1976-82

  • Brake pads for the 407-onwards (EBC & others) are frequently listed for sale on EBay.
  • 408 MkII Brake Pad Set Rear Calipers are as fitted to Jaguar Mk2/V8. The Handbrake Pad Set, are also as fitted to the Jaguar Mk2/V8
  • 407- Fighter are available from EBC. EBC Brakes Direct Tel: 0845 225 5011 There are several other sources for EBC brake pads.




 Brigand, Beaufighter and Britannia

Click here to download (TYPE, 624KB)


Currently listed at Discount Car Parts at £192.70 as of August 2010. A French site lists the Cylinder as fitting Land Rover: Range Rover Mark I (EA, NA , HAA , HAB, HAM, HBM , ER , RN) 3.5 ( 132Ch ) Braking System AP Lockheed. They are currently selling at half price = €174.84 ~ approx. £145.70 from Mister Auto.


Front Calipers Models Dates
L.H. Girling 64033006 / Dunlop VB 1198B 407 & 408 1961 – 65
R.H. Girling 64033007 / Dunlop VB 1198A 407 & 408 1961 – 65


Also Fitted To Model Dates
Alvis 3 Litre TD21 1961 – 64
Aston Martin DB4 1959 – Oct 60 / 1964 On
Jensen 541s 1961 – 62
Jensen CV8 MkI & II Oct 1962 – June 65
Jensen CV8 MkIII July 1965 – 66
Jensen Interceptor 1967 – 68


Rear Calipers Models Dates
L.H. Girling 64033142 / Dunlop VB 1284-B 407 & 408 1961 – 65
L.H. Girling 64033143 / Dunlop VB 1284-A 407 & 408 1961 – 65


 Note: The catalogue notes that these were used only on Bristol Cars.

SP2556 Service Kit Also Used On Models Dates
Alvis 3 Litre TD21 1961 – 64
Aston Martin DB4 1959 – Oct 60 / 1964 On
Daimler Majestic Major 1960 On
Daimler Limousine DR450 1961 On
Daimler V8 2 1/2 Litre 1962 On
Ferrari Berlinetta Coupe
Cabriolet 250GT
1961 – 64
Ferrari 330GT 1963 On
Ferrari 248GT & 275GT 1964 On
Fiat Arbarth 2200 1960
I.S.O. Revolta GT Coupe 1962 – June 63
I.S.O. Revolta GT Coupe July 63 – 1964
Jaguar XK15 & 150S 1958 – 59
Jaguar 2.4 & 3.4 Litre 1958 – 61
Jaguar 3.8 Litre 1959- 61
Jaguar 2.4 & 3.4 & 3.8 Litre 1961 – 64
Jaguar 240 & 340 1967 – Oct 69
Jaguar 3.8 “E” Type (First 5,000 1961 – 64
Jaguar 3.8 “E” Type (5,001 on) 1961 – 64
Jaguar 4.2 “E” Type 1964 – 68
Jaguar 2+2 “E” Type (XJ8) 1966 On
Jaguar 3.8 Litre Mk X (First 1,500) 1961
Jensen 541s 1961 – 62
Jensen CV8 MkI & II Oct 1962 – June 65
Jensen CV8 MkIII July 1965 – 66
Jensen Interceptor 1967 – 68
Lancia Flaminia GT & Sports 1960 – on
Lancia Flaminia Saloon & Coupe Undated
Lancia Flavia Saloon 1961 – 68
Lancia Flavia Coupe 1961 – 68
Lancia Flavia Coupe 1968 – On
Lancia Fulvia Saloon & Coupe 1964 – On
MGA Twin Cam 1964 On1 – 68
Rover 2000 1963 – 66


SP2555 Service Kit Also Used On Models Dates
Alpha Romeo T2 Competition 1963 – On
Daimler V8 2 1/2 Litre 1962 On
Facel Facella 1964 – On
Ferrari 248GT & 275GT 1964 On
Fiat Arbarth 2200 1960
I.S.O. Revolta GT Coupe 1962 – June 63
I.S.O. Revolta GT Coupe July 63 – 1964
Jaguar XK15 & 150S 1958 – 59
Jaguar 2.4 & 3.4 Litre 1958 – 61
Jaguar 3.8 Litre 1959- 61
Jaguar 2.4 & 3.4 & 3.8 Litre 1961 – 64
Jaguar 240 & 340 1967 – Oct 69
Lancia Flaminia GT & Sports 1960 – on
MGA Twin Cam 1964 On1 – 68




How shock absorbers work

(Extracted by K. Lutz)

Shock absorbers don’t really absorb shock, they dampen it, hence they are often referred to as dampers. Why is this important for you to know? To improve ride quality. Basically put, a shock absorbers sole purpose is to dampen the compression and rebound of any suspension system by controlling the speed at which a suspension cycles. Without them, your car would continue to bounce up and down until the kinetic energy is finally dissipated from the suspension’s springs (e.g. leaf springs, coil springs, torsion bar, etc.) and sea sickness may follow.

Now let’s think about the law of conservation of energy. With this law in mind, shocks will perform two functions. The first function is to slow the suspension’s cycling of compressing or rebounding. Secondly, since energy can’t be destroyed, the shock transforms the kinetic energy into heat as it dampens the “bouncing” of the springs. That’s it. That’s what a shock does.

Or otherwise put – in a vehicle, it reduces the effect of travelling over rough ground, leading to improved ride quality, and increase in comfort due to substantially reduced amplitude of disturbances. Without shock absorbers, the vehicle would have a bouncing ride, as energy is stored in the spring and then released to the vehicle, possibly exceeding the allowed range of suspension movement. Control of excessive suspension movement without shock absorption requires stiffer (higher rate) springs, which would in turn give a harsh ride.

Shock absorbers allow the use of soft (lower rate) springs while controlling the rate of suspension movement in response to bumps. They also, along with “bounce” in your tyres, dampen the motion of the unsprung weight up and down on the springiness of the tyre. Since the tyre is not as soft as the springs, effective wheel bounce damping may require stiffer shocks than would be ideal for the vehicle motion alone.

Spring-based shock absorbers commonly use coil springs or leaf springs, though torsion bars can be used in torsional shocks as well. Ideal springs alone, however, are not shock absorbers as springs only store and do not dissipate or absorb energy. Vehicles typically employ both springs or torsion bars as well as hydraulic shock absorbers. In this combination, “shock absorber” is reserved specifically for the hydraulic piston that absorbs and dissipates vibration. Below are some images which illustrate these principles, and the technical features of dampers.