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Brake Master Question

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Bryan Boyle:
As you all know...been working on 3291R for a couple years...and I think it may be time to address the existing master cylinder issue...it slowly weeps fluid out (I think, through the rear seal...but...and, while I can bleed it to a solid pedal that lasts for a few months, obviously it's not a case of 'just keep doing it and it will get better.")

So...I've collected a bunch of candidate MCs:

1. OEM Toyota F10 pickup
2. TRW Triumph Spit slope top .70
3. Original TCS cylinder (slope top)
4. From my parts stash of breaking up 4 S2s...a couple of S2 masters in serious need of rebuild, with a spare new, in the box, S2 reservoir.

Now, having removed the boosters,  I've a non-boosted brake system.  I'm thinking that (assuming I will re-plumb and remove the excess bundy going to the back then returning to the front...) the most satisfactory results may be found by sending the S2 MCs out to Apple and resleeving/rebuilding to S2 spec (stepped bore, etc).  However, I'm wondering if there is enough clearance to use the large reservoir (as on the S2), with its increased capacity, in place of the slope top original TC style without having to do fiberglass surgery.

The advantages to using the Lotus-spec MCs is that

1. There would be no need to do bundy splicing to account for the feed port location on the master...and if I can fit the larger reservoir without carving fiberglass...well, that would be a plus too (not that I'm against it in the goal of increasing the capacity....),

2. Removing the out-and-back tubing for the front calipers would simplify and remove multiple splices to account for the booster and PDWV removal, and

3. The bores are close enough by using the S2, (accounting for the different size of the rear brake cylinders) for the car's dynamics (as far as I can tell).

Open to thoughts.   

berni29:
Hi Bryan

I cannot help you with your specific question (and are also interested in the answer), but may I ask why you removed the dual boosters? Was it just the additional complexity and weight that made the standard system unattractive? Its something that I will also be dealing with at some point. I would like to keep my car original, but when it comes to things like this I prefer the most elegant solution and just keep the original parts on a shelf somewhere.

Do people loose points for removing the boosters?

All the best

Berni

Grumblebuns:
Bryan, if I understand what you are asking you are determining what master cylinder to substitute after removing your original MC and removing the boosters with the requirement of having decent reservoir volume. The S2 MC would be the first choice since this would be a simple bolt on effort provided the reservoir is in decent shape. The only problem I see in using the original fittings and flare end is possible leakage when fitted to the replacement S2 MC. Cranking down on the fitting may or may not stop the leak.

The Spitfire MC is a good option since it is a semi bolt on. The ports being on the opposite side requires jumpers and the ports are probably metric. The downside is the severely sloped reservoir. I have not looked at the requirements but installing a remote reservoir may allow you to meet your volume requirements.

The only alternate MC that I've had any experience with is the Datsun/Nissan F10 that the PO installed on my long sold JPS. The braking on that car was outstanding with great feel and stopping power. What ever brake pads were installed on that car made all the difference.

I'm in the middle of installing the Courier MC on my TCS. The project has been stalled for a while due to other more urgent projects. With the ports being metric I had to cut odd the original fittings and splice in new jumpers with metric fittings. One problem I ran into was the super tight clearance between the MC ports and the bodywork of the bottom of the nose section. There is about one inch of space to make the tight 90 degree bend without kinking the line.

 

EuropaTC:
Hi Bryan,

I had the Spitfire 0.7 dual circuit m/cyl on my car for a while at one point and there are a several guides on how to do it on the forum.

When I did mine I removed the wedge shape reservoir and replaced it with a remote one from a Land Rover. Apart from having a greater capacity and being easier to see, it also came with a low fluid warning switch.  Anyway, the 0.7" cylinder is ok with non-servoed standard brakes so you know that one will work.  I no longer have that on my car but I do have one on the Elan, again without servo assistance but with the larger piston P16 calipers and it's fine.

If you are currently using the OEM Lotus m/cylinder, am I correct in thinking the later Specials had a larger bore to handle a larger rear brake cylinder ? If so, you might not like the additional travel with a 0.7" bore or at least it will take some getting used to. But the big plus is that it's a well trodden path, bolts straight into the chassis and so there's no real surprises in store.

Brian

BDA:

--- Quote ---...am I correct in thinking the later Specials had a larger bore to handle a larger rear brake cylinder ?
--- End quote ---

According to the parts manual, all the TCs and TCSs used the same master cylinders.

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