Should i fit a brake servo to my 1968 S3 elan?

[oldelanman]

And be very aware that there were different versions of the same servo fitted to the Elan and the Plus 2:

Lockheed/Delphi part no. LR17818 with a slave cyl bore of 11/16" in the Elan with a boost of 1.90:1, and
Lockheed /Delphi part no. LR18221 with a slave bore of 5/8" in the Plus 2 with a boost of 3.00:1

They are indistinguishable on the exterior.

Aren't Lockheed servos aftermarket replacements? I thought OE servos were all Girling - MK2A on early cars and Mk2B later. These have the cylinder bore size cast into the body and it's 5/8" for the Elan (not 11/16" as the Lockheed) I don't know about the Plus 2 though.

[robertverhey]

My understanding was that servos became common around the time that disc brakes did, because of the loss of the "leverage" component provided by drum brakes. If you mentally compare the way drum brake cylinders and disc brake cylinder apply force to the brake shoes / pads, it stands to reason that pedal pressures would be higher with discs, and even higher again with four wheel discs..... But that's interesting about the Elise.....wonder how they designed them so that pressures remained moderate? Great way to add lightness!

[UAB807F]

(part quote)
But that's interesting about the Elise.....wonder how they designed them so that pressures remained moderate? Great way to add lightness!

From what I can see it's down to the combination of m/c bore, piston diameters & the geometry/leverage from the brake pedal itself. IMO the Elise has a lighter pedal than many modern servo'd cars and was one of the reasons I started to look again at the system on my Elan.

[worzel]

Hi

Only my experience- you'll have to make up your own mind on this.

Purely for simplicity I eliminated the servo on my sprint. Dropped the master cylinder size to 0.625 from 0.7. Wasn't too impressed with the stopping ability. Tried various pads- greenstuff etc. Only marginal improvement. Everything changed when I fitted genuine old stock Triumph GT6 Mk 1 pads (Mk1's didn't have servos fitted by Triumph). Purely subjective this but I'd say the brakes and the pedal pressure feel about the same as my old servoed system. Only slight difference is intial reaction to light pedal pressure (when braking at low check speeds)- slightly less bite. I definitely wouldn't return to the servoed system as I don't see any point. You have to get the earlier softer pads though- not the "modern" GT6 ones.

Regards

John

[Sea Ranch]

Thanks for this tip, John. I've read this elsewhere on the forum (perhaps your post then, too).

Dummy/lazy question: are the pads on Plus 2 the same as on Elan? Can you suggest a supplier for old stock GT-6 pads? (I had a GT-6 Plus back in the day; loved it)(but not the swing axles or crazy oversteer )

Randy

[Robbie693]

Hi Randy,

are the pads on Plus 2 the same as on Elan?

no - the Elan pads are different as the Plus 2 has bigger front disks. I believe John has fitted Plus 2 disks and calipers to his Elan, hence his GT6 reference

Cheers

Robbie

[worzel]

Hi

Apologies- I should have mentionerd the fitting of the plus 2 system on the front- GT6 pads obviously won't fit the std 2 seater calipers. If you're looking for pads try ebay- but I'm not sure which ones you'd need- the starting point I suppose is to see what other cars of similar weight to an elan used non-servo spec pads- possibly Triumph Spitfire. I'd only stress that you need "old stock" pads not their modern counterparts.

Regards

John

[Sea Ranch]

Thanks, guys. Got it: the Plus 2 has different/larger calipers on front, same as Elan at rear.

[Elan45]

John,

If you really wish to improve your braking on a non-servo system, you might consider going back to the stock diameter discs and stock calipers. I can understand the desire for larger brakes if you were racing the car, and you needed the extra heat capacity of the bigger brakes. But I don't think you are racing and all you've done is un-balance your brakes. Consider that the +2/ GT6 calipers existed on TR3-TR4, Healey 3000 and other heavier cars than the Elan. S1 Elans had smaller 12 size caliper, upgraded to the 14 size on all subsequent Elans. That was Lotus's engineered solution.

Roger

[Galwaylotus]

Sound logical advice.

[RedS4]

Servos are definitely a matter of choice. When I bought my Elan the previous owner had bypassed the servo. Great pedal feel but too uncocerting in traffic for my taste so I pumbed the servo back in. Unfortunatelly nine years of no use caused it to play up and so I had it repllaced (I wanted it serviced to maintain originality but the cost was over 50% more than repacing it! ).

The new servo feels great and inpires confidence when braking - so I say "yes" to servos - but as the others have said, it is a matter of personal choice.