Hello, I’m in the process of trying to reassemble a 67 FHC from boxes. In talking to Mike Ostrov this Saturday the question of whether to refurbish and install a Servo came up.
His opinion was that I’m better served replacing the existing MC with one having a 0.7" bore. He thought they were available in the original single pot design for a single circuit car.
Mike remembered that it took a near gorilla effort to apply pedal pressure and that there was no difference in the stopping distance between servo and non-servo cars.
In looking around I’ve seen where the suppliers all carry them but I haven’t seen one driveable Elan that has them installed.
I’m trying to stay close to spec yet keep things practical to ensure having a chance to have fun with the car for the next several years. Proposed improvements include a dense radiator core, electric cooling fans, CV axle conversions, alternator, relays, electric fuel pump.
John,
My 72 elan sprint coupe does not have a servo and it stops just fine…I wouldnt say it requires much pedal effort …im curious to hear from others what they think…
DAvid
My Elan is unboosted and the pedal is heavier than a typical modern car. I prefer it that way as I find modern cars brakes over sensitive. They are deliberately this way as the ABS takes care of lock up and the makers actually want you to lock the brakes in an emergency. Modern high coefficent of friction road pads such as Geen Stuff or Ferodo DS2500 make the pedal effort signficantly less than orginally 40 years ago and acceptable in modern terms.
My Plus 2 is boosted and the pedal pressures are comparable to a modern car. Makes it a little to hard to control the brake modulation compared to the unboosted Elan but easier to drive in a mindless sort of way.
In the end going boosted or un boosted is very much a personal preference I believe
Do you know what good bicycle brakes (e.g. cantilevers on mountain bikes) feel like? That’s just how much feel you get on an Elan without a servo… Very nice
It far outweighs any heaviness of pedal - you soon get used to it.
Other advantages: one less thing to go wrong, saves some weight for improved performance & fuel consumption
The baby Elan servo was 2:1. Not much. But servo equipped cars also had different master cylinder pistons and caliper piston sizes which cut down on the effective boost ratio.
The comments you read on this site about owners that converted from servo to non-servo and are complaining about how hard the pedal effort is didn’t take this into account.
If you want to convert back, call the chaps at Dave Bean and follow their recommendations for master cylinder bore and caliper size. You may have to replace the calipers. Both Mike and Rohan are correct in their comments.
Also, be sure to use braided brake lines. It makes a substantial difference in the brake feel and cuts down on pedal travel.
I have never had a servo in my Elan, and have never felt the pedal effort excessive, nor have I had negative comments from anyone who has driven the car. But different people have different sensibilities. And it is a definite chore going to a modern boosted brake system, and throwing the passenger through the windshield the first time I brake. Modern cars require tippy toe braking, not the firm linear pedal feel you get with a non-boosted system. In the end, it depends on what you want.
I believe your statement “But servo equipped cars also had different master cylinder pistons and caliper piston sizes which cut down on the effective boost ratio”, is incorrect.
The Baby Elan Parts Manual does not differentiate between boosted master cylinders and calipers. I believe early S1’s used Girling LF12 calipers but all later Elans used the LF14’s. Rear calipers were all the same, even for the +2’s. Early master cylinders, up to chassis number 4108 were 0.625 inch diameter then changed to 0.700 in diameter for chassis numbers up to 7399. Super Safety and Federal Elans then went to a dual braking system with a 0.750 inch bore at chassis number 7400.
If you want more breaking pressure for a given push on the pedal, there are two basic ways of doing it.
decrease the master cylinder bore size
increase the front caliper piston bore size
can be accomplished by changing the master cylinder from a 0.700 inch bore to a 0.625 in bore. Be careful though, the 0.625 bore master cylinder will displace less fluid, but at a higher pressure for a given push on the pedal. The pedal displacement will be greater but the fluid displaced will be less resulting in less potential displacement of the caliper pistons, but is probably ok.
Front caliper bore size can be increased by fitting +2 calipers or perhaps aftermarket ones. The same caution applies, less displacement of the pistions due to larger diameter pistons and more required fluid movement, needs to be checked for suitability, but is also probably ok.
Combining 1 and 2 should noticeably increase stopping power for a given pedal presssure but will require an even larger pedal stroke to achive a given clamping pressure. You just need to be sure there is enough fluid displaced to fully realize the reduced pressure braking benefits.
I guess the key to making the combination 1 plus 2 work, is to ensure disc runout in minimized. This will ensure that that the required piston displacement at the caipers will be minimized and so will the resulting brake pedal displacement.
Now that I look back in the Service Parts List is see you are correct. I was going from memory where front calipers were available in 1.89, 2.00, and 2.12 bores. But the List does not bear this out.
Master cylinders were available in .625, .7, .75, and .875 sizes and in single and dual forms. The List is not totally accurate here, since my chassis 7988 has a single master cylinder. Maybe just a Lotus anomaly, part of the production process.
As you point out, it is important to have a well maintained brake system when using a small master cylinder or large caliper bore in order to minimize slop and thus pedal travel in the system. Also, using ss braided brake lines minimizes pedal travel, and gives a more linear pedal feel.