Lotus Elan

Plus2 servo replacement

PostPost by: john.p.clegg » Mon Jul 18, 2016 12:10 pm

Dear All

For a while I have been thinking of improving the brake set-up on my Plus2 , this has been brought about by my need to tinker and retirement from work...as a consequence of the latter ( lack of exercise and on-coming old age ) I find the brakes are no where near as good as my daily pensioners shopping trolley.
The standard servo ( Lockheed ) is a Type 7 with a ratio of 3.00:1,the next step up being 4.25:1 which is what I am preparing to fit.

Any thoughts before I go ahead...Over-servoing,different pad materials etc.etc. bearing in mind the car is driven " spiritedly" whenever possible.

N.B. Also has ABS

John :wink:
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PostPost by: c42 » Mon Jul 18, 2016 12:56 pm

Rear brake pressure limiter.

John
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PostPost by: bill308 » Mon Jul 18, 2016 8:30 pm

Hi John.

I'd try a different set of (street) pads before enhancing the servo. The cost should be relatively low. Another possibility is a smaller bore master cylinder, provided there is still enough volume..

Are you sure all 4-brakes are working properly and doing their share? The fronts of course, will do more than the rears, because of weight transfer.

A servo ratio of 3:1 is pretty significant. I suspect many, if not most Elan folks, don't use boosted brakes. Going to a 4.25:1 boost ratio yields a (4.25/3=1.416) 42% reduction in pedal pressure, for a given caliper clamping force. Still, this is less than 1/4 the pedal pressure of an unboosted system.

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PostPost by: john.p.clegg » Mon Jul 18, 2016 9:42 pm

Bill

Thanks for your input,one thing in the back of my head are the number of posts where people are reinforcing the pedal box mounting...I don't think that is due to the accelerator pedal or the clutch operation ??

John :wink:
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PostPost by: rgh0 » Tue Jul 19, 2016 10:29 am

John
if I recall correctly I have read the Elan used a 2:1 ratio Girling booster originally (where fitted on SE models) and the Plus 2 used a 3:1 ratio booster.

I find my Plus 2 with the standard Girling booster is as light on the brake pedal as any modern hatchback and in reality a little to light if you don't have ABS as its to easy to lock up the brakes. This is using standard pads not modern high coefficient pads. i ran the Plus 2 for a while without the booster and high coefficient pads with very similar pedal effort.

My Elan without a booster using modern high coefficient pads has a similar pedal effort. I use a racing pad and when these are hot I only need to lightly brush the pedal to get good retardation and can easily lock up all 4 wheels with a medium controlled push.

I also don't understand the need perceived by some to reinforce the pedal box area except for a concern over long term degradation of the fibreglass or the wrong brake system setup

While pedal effort and feel is a very personal thing, based on my experience, I don't believe you should need a 4.25 ratio booster for a plus 2 even if you want a modern level of pedal effort. I would look at the pads and disk condition and rest of the system first.

cheers
Rohan
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PostPost by: CBUEB1771 » Tue Jul 19, 2016 5:18 pm

john.p.clegg wrote:I find the brakes are no where near as good as my daily pensioners shopping trolley.


Some things do improve with time. My daily driver performs better than my +2 in every category other than fuel consumption. However the +2 remains very enjoyable and so I still keep it. In my view the +2 with 3:1 maximum servo gain is a bit over boosted. It is not difficult to lock the fronts. I have tried removing the servo and going to a 5/8" bore master cylinder but found that the pedal effort was disconcertingly high and completely out of balance with the light touch required for the steering, clutch and gear change. I am thinking of going to a 2:1 servo in hopes to achieve better overall balance. I have a feeling that going to 4+:1 servo gain will reduce pedal effort but not really improve braking, locking will be too easy to achieve.
Russ Newton
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Elite S2 (1962)
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PostPost by: john.p.clegg » Mon Jul 03, 2017 9:13 am

Just an update,fitted the 4.25:1 and tried it ,t oo fierce , re-fitted the 3.0:1 , much better "feel".

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