Brake Master Cylinder for S1

[Certified Lotus]

My 1964 S1 has a non standard brake master cylinder (for the period of the car). It looks to be the master cylinder for a later model Elan. Any advise on the pros and cons of keeping this version vs installing the proper one that orinally came with the car (I have the right version new in box).

[patrics]

Hi,
Assuming that it is a 0.7 cylinder then there are no down sides.
You have a twin hydraulic circuits, one feeding front and the other the rear ware as the standard one is a single circuit feeding both.
If it is 0.7 then these were fitted to Caterhams and Morgan's
If it is larger than 0.75 then the pedal effort will be very high.

Regards
Steve

[Certified Lotus]

Thanks Steve. The pedal effort is very high. How can I tell what size cylinder model this is?

[patrics]

Hi,
There should be a tag on it like the this one - removed this from mine as wanted a slightly larger cylinder

[oldchieft]

The two master cylinders are different, the first one is the early type.

That has the connections on the other side and the reservoir is fitted with cir-clip on the front and a pair of screws at the back. The one with the flange up and down is the rare one.

Both were used in the 70's and 80's on Morgans.

Jon the Chief

[Galwaylotus]

If you have a tandem master cylinder I would recommend not returning to a single circuit system. Originality is not always the best option where safety is concerned. I cut a brake hose once on a previous Elan and suffered total brake failure. Fortunately I was going slowly in first gear when it happened and no one was driving on the cross street when I sailed through the intersection!!
I replaced the single 0.7 inch m/c on my current Elan with a 0.7 inch tandem m/c so if I do have a failure in one circuit for any reason I'll still have braking on the other.

[Certified Lotus]

The two master cylinders are different, the first one is the early type.

That has the connections on the other side and the reservoir is fitted with cir-clip on the front and a pair of screws at the back. The one with the flange up and down is the rare one.

Both were used in the 70's and 80's on Morgans.

Jon the Chief

Jon, do you know if mine is the right size? Without taking it off the car I can't see any markings on the unit.

[oldchieft]

Bit of a problem that, the casting number is no help.

The plastic tag on the body is what you need, If you don't have that then you need to remove the thing and dismantle it.

Also the type on my Morgan was a stepped bore, the reason for that being the front part would have a larger area then the rear if was the same bore through the length.

This is because the rear part has an annular area and the front is full bore, so for a 50/50 split you need a stepped bore. this is needed for a diagonal split system to get balanced braking. If you have a front rear split the this is not needed and you put the larger area to the front and the smaller to the rear, then you balance by what size cylinders or callipers you fit.

When mine was away for overhaul and sleeving they lost the tag, for a while thy lost the whole thing and tried to fob me off with someone else's! That was how I found out about the up/down side to side flange.

If you have the tag then a good specialist place will get the information for you. Hope that helps.

Jon the Chief