Lotus Elan

Brake Servo rebuild vs new servo

PostPost by: Peter +2 » Thu Nov 25, 2010 12:33 am

Gentlemen, a question please,

I have a 68 Plus Two with an original but failed brake servo. Can anybody tell me what is the percieved wisdom of having a rebuild at somewhere like Classiccar Automotive versus buying a new servo at a similar price?

I am not sure myself and I am about to go one way or the other?

Thaks

Peter
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PostPost by: garyeanderson » Thu Nov 25, 2010 7:44 am

495 topics with servo in them, I guess its kind of a popular subject. I don't know much about them but they seem to cause a lot of problems/questions. I wouldn't use one on an Elan S1-4 but I think that they are kind of necessesary for a Plus2. Here is a link to the search I did with SERVO

http://www.lotuselan.net/cgi-bin/search ... oom_sort=0

25 pages of topics should keep you reading until this discussion gets rolling again.

Gary

p.s. I hope everyone has a great Thanksgiving day if you observe this time as a holiday.
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PostPost by: AHM » Thu Nov 25, 2010 11:13 am

For a rebuild I can reccomend classicar automotive.

I've rebuilt an Elan servo myself and I would say that if it just a seal kit it is ok, but if you want a propper job it is probably worth the money to get it remanufactured.

new vs old - A modern one is going to look like a modern one in an old car. If you are not bothered about that sell the old one even dead they fetch good money.... which rather tells you what the concensus is!

Simon
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PostPost by: Peter +2 » Thu Nov 25, 2010 2:03 pm

Gary / Simon.

Thank you both for your help here.

Regards

Peter
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PostPost by: gerrym » Thu Nov 25, 2010 6:08 pm

Peter, for the Servo rebuild versus new I recommend No Servo!.

You will need front brake pads with a better coefficient of friction. Greenstuff pads have got the thumbs up from Plus 2 owners without servos (on this forum). Of course everything else should also be in good shape (ie minimum run-out on front and rear disks, seals in good condition).

Cheap to try.

Adds simplicity and avoids some rather nasty hidden failure modes.

Regards
Gerry
Last edited by gerrym on Thu Nov 25, 2010 10:44 pm, edited 2 times in total.
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PostPost by: alaric » Thu Nov 25, 2010 7:03 pm

Hi Peter. Gerry's quite right in his post. I did a response for you earlier but somehow managed to press the wrong button of the microsoft gods weren't smiling at me for some reason, and I lost the whole lot. I went off in a huff and cleared out the greenhouse instead. In short I was saying that I had my Girling MkIIB rebuilt some time back, but it aged on the shelf and was useless when I fitted it as the greese had conjealed. I also found the rubber elbow split and discovered the internal ball bearing valve looked old so hadn't been replaced. So I wasn't impressed with the rebuild and it cost ?185 from the experts.

The alternative is to try a lockhead servo - there's a version with the same gain 1:3, which is advertised on ebay. The issue with these that's been reported here is they lock on due to lack of a return spring - sure the others'll correct me if I am wrong here - but they're fine if you fit a spring. My view was to rebuild the girling unit rather than messing with a different make. But people on the forum have used the lockhead and it appears fine with the spring fitted.

My plan is to leave the servo out and see what it's like - I've never driven the car anyway so won't know the difference. Once the car's on the road fitting the servo back in wouldn't be difficult.

One word of caution though; what to tell the insurance? I was warned about this when enquiring about a tandem master cylinder from the supplie in Aus whose name escapes me. What have others done about this?

If anyone can offer benefits of the lockhead unit I'd be interested to hear.

Sean.
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PostPost by: kstrutt11 » Fri Nov 26, 2010 10:00 am

I have deleted the servo on my +2, with green stuff pads and and the next size down master cylinder they are fine, the efforts are higher but the feel is much better and they are more progressive.

Kevin
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PostPost by: gerrym » Fri Nov 26, 2010 11:05 am

Sean, off topic here but I have fitted a tandem master cylinder from a late model Spitfire. It's not completely straightforward, because a new reservoir is required and the bodywork relieved. The pushrod also needs shortening. Details are in one of my previous posts. My rational was that without the servo, tandem cylinder installation becomes feasible. Circuits are split front/rear.

The rear axles on the Elans are very close to the brake pipes and especially with rubber donuts, have been known to take out the hydraulic pipes which would result in total brake system failure for a single line system.

My other reason was the reduced efficiency required from the handbrake for a dual line system.

Regards
Gerry

PS, does anyone have any photos of the rear brake pipe routing on a Spyder chassis. Mine looks a bit exposed where it goes through the front "bulkhead"
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PostPost by: alaric » Fri Nov 26, 2010 12:33 pm

Gerry, thanks for that. I did indeed read all your previous threads on the dual circuit options when I was looking into it. I was getting serious about buying a master cylinder rather than spending the money on a servo. The guy at elanfactory in aus refused to sell me the tandem master cylinder on the grounds that I was using the car on the public roads and brakes are safety critical. I can only assume there's a precedent that's forced that position for the company. I think he was concerned about his liability. Was insurance an issue for your conversion?

For interest here's a link to the cylinder that I was looking at. The write up suggests it's for road use rather than just racing so I remain puzzled by the response that I received.

http://www.elanfactory.com.au/pdf/produ ... linder.pdf

Regards.

Sean.
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PostPost by: gerrym » Fri Nov 26, 2010 12:56 pm

Sean, modifications are part of life for the Elans, as even the current repro stuff is not exactly the same as original. And how far do you go? Fit 30 year old tyres because they were current at the time? Wheels that are original but fatigued?


Mike A had some very knowledgeable comments to make which are probably worth referring to.

As far as brakes go, I have no problem with a "Safety Upgrade" to a tandem system from a single system. I'm probably more confident to use a standard Spitfire 1500 master cylinder than than one with lineage a little harder to trace (ie the Mitsubishi Elan Factory one). On practicality grounds, there's future spares or servicing issues to be aware of.

Please bear in mind however that an insurance policy is a contract between you and the Insurance company so you need to pay attention to disclosure requirements.

Regards

Gerry
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PostPost by: rdssdi » Fri Nov 26, 2010 9:04 pm

I replaced the original Girling servos with the Lockheed. The Girlings were in horrible condition and I had heard of problems with rebuilding them.

As you may be aware the Girling boosters (two for dual circuit) were mounted on the inner fender. ON LHD cars they were very close to the exhaust manifold. As the new Lockheed servos are a bit larger it makes positioning dual servos in the same location a difficult task. I overcame this by mounting one on the inner fender and one in the nose.

It took a bit of plumbing and I used a remote air "intake" for the front mounted booster (supplied with kit) to avoid water ingress. The pedal pressures are light and the brakes have good feel.

Bob
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booster.jpg and
You can see remote breather. "T" mounted rad support. Hose goes down to breather cap. Also see vac line.
boosternose.jpg and
During install. Rad and hoses not installed yet.
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PostPost by: mikealdren » Sat Nov 27, 2010 9:07 am

Thanks Gerry?!?

I worked for Vauxhall in the 1970s and spent a couple of years at Millbrook testing braking systems to the various regulatory standards of the time. Even then, the standards (British, European and Swedish) were quite old, they changed in details but not greatly.

Amongst other things, they looked at overall performance, fade performance and the ability to meet a secondary braking standards in the event of any single point of failure. For single line systems, the traditional solution was to use the handbrake but there were plenty of issues with this. One of the problems (especially on commercial systems including vans) is that the rear wheels may be lightly loaded so it isn't possible to get much braking performance before the wheels lock. This led to triangular split systems with twin front pistons giving front and one rear on each circuit, this was particularly used on truck air systems.

The Elan, as we all know, always had a marginal handbrake so a split system has real advantages with no downside. If you lose your braking, it's far better to be able to brake on the pedal through the remaining circuit rather than trying to grab the handbrake, especially when it's under the dash! It's also much easier to modulate the braking through a pedal rather than a lever.

As long as the dual circuit master cylinder has the same diameter as the original, there should be no noticeable change in performance at all.

Actually, from a performance point of view, once you change the pad material and M/C diameter and travel to compensate for a non servo system, you are certainly moving away from what was designed by the manufacturer. Changing pad material is far more likely to cause problems that simply dispensing with a servo or going to a split system.

Of course, the car also had to be able to pass the secondary standards with a failed servo so systems have to work without a servo. The main purpose of the servo is to reduce pedal effort and the legal tests measured performance against pedal load. In early applications the servo was sometime an extra and in many cars, you could easily dispense with it. I ran a Viva without a servo and found the brake feel better than standard servo system. The loads were higher but well within legal limits.

Mike

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PostPost by: Peter +2 » Sun Nov 28, 2010 8:11 pm

Thank you all for all your help and advice, I would have been interested in the dual master approach, but having just rebuilt the pedal box with new Brake and Clutch master cylinders I will stay with that approach. I will definitely stick with the servo as when I drove a Plus 2 as a daily driver all those years ago (20+) having a servo seemed fine. I will probably go for a rebuild at Classicarautomotive. But who knows, by the time I have completed the front suspension overhaul and replaced the sills I my have changed my mind.

Thanks again all.

Peter
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