Lotus Elan

Servo or not to servo........?

PostPost by: pauljones » Sat Jun 25, 2011 10:08 pm

As I was looking under the bonnet to look at the clutch routing,I thought it would be easy to have a flexible pipe to the servo or even to bypass it completely,is it ok to miss out the servo and do I need to mod anything else,like pad compound,master cylinder ect???

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PostPost by: stugilmour » Sun Jun 26, 2011 7:11 pm


As you didn't get a reply yet, will try to provide bit of info and a few clarifying considerations. Most info below learned from previous threads rather than personal experience. Gerry M has done a bunch of work regarding servo removal & required mods, so may be able to clarify any details. Short answer is mods are advised but you can run with servo by-passed if you wish.

  • Assuming you presently have one servo? The federal cars like mine over here have two servos and a dual brake system split front and rear, whereas typically the home market cars used a single hydraulic system and one booster.
  • Decide when making mods whether you wish to change to a dual system (harder mod, changes to piping in difficult areas to reach with body on, dual master cylinder) or stay with single system (simpler, easier to get master cylinder, relatively easy piping changes on top side).
  • For servo bypass and/or removal, results reported are mixed, so probably a strong element of personal preference. One person's high pedal effort equates to another person's spot on brake performance.
  • General thought is non-servo system should use a smaller diameter master cylinder than you will have installed now. Posts in archives can be a bit confusing for recommended diameter to use, as they may relate to two seater with or without servo, two seater with Plus 2 brakes with or without servo, Plus 2 with or without servo, and/or previously mentioned personal preference.
  • General design principle is a smaller diameter master cylinder gives lower pedal effort by longer travel.
  • General thought is permanent removal of the booster in the Plus 2 should be accompanied by strengthening of the pedal box area. Alternatives suggested include extra fibreglass, welded bracket (Sean has done up a nice drawing), or both.
  • Several folks have by-passed the servo temporarily with stock master cylinder in place to check things out. Seems to be generally conceded it works but pedal effort is too high.
  • If you want to purchase a dual circuit master cylinder in either stock or custom diameter, I understand the 'stock' unit is NLA. Believe the selected alternatives that work generally have the discharge ports on the opposite side of the casting, and therefore changes to piping required. Some folks have had their existing dual M/C re-sleeved to a revised diameter by various specialists, including White Post in New York state.
  • General consensus the pads should be changed to something like Green Stuff to improve braking.

I decided to stick with my dual boosted system as I was able to get it working.

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PostPost by: Galwaylotus » Sun Jun 26, 2011 7:48 pm

As Stu said, there is no problem bypassing the servo to see the effect. When mine locked up I did just that and wound up removing it altogether. Other mods:
AP Racing tandem master cylinder 0.7 inch diameter (standard part for Caterham Seven).
Steel-braided brake lines all arounf (Aeroquip from Miles Wilkins).
EBC GreenStuff pads on front calipers.
Low speed stops require a bit of a push but I soon got used to that. Higher speed - normal driving- braking is fine, but then I have a S3 two seater. :wink:
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PostPost by: kstrutt11 » Sun Jun 26, 2011 9:17 pm

I have deleted the one on mine, I could never bleed the brakes and it was all too easy to lock up the wheels under braking due to the lack of feel, I have a m/cyl one size down from the original (.625"?) greenstuff pads and aeroquip lines, it's now much more progressive with a much better pedal feel, the efforts are also fine.

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