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MG Midget and Sprite Technical - dual master brake cylinder?

I have a question about the brake master on my '74 midget. I was told by some knowledgeable people how to connect the pipes to the PDWS. Then yesterday I was shown a car with the pipes connected the opposite way.

I have been reading every manual I can find and searching forums but cannot find the answer. And because of the lack of information I wonder if it makes any difference.

So here is the question. Is there any difference which port on the dual master cylinder is connected to the front brakes?

tomshobby

Tom, on my car the line to the front brakes was connected to the rear most port on the master cylinder. The line was a bit larger OD but the same ID as the one for the rear brakes. The flare nut was also a larger wrench size as I remember. I do believe that it makes a difference as a majority of the pressure bias is applied to the front section of the master cylinder so that output would need to go to the front discs. Here's a photo of the setup just before I changed it out for a three cylinder setup. Note the line nearest the firewall appears to be slightly larger in diameter.


B Young

Thanks Bill,

That agrees with the ones other than for the car I was looking at yesterday. And it makes sense.

BTW - I hope to meet you at the 50th. I have a conflict but plan on being there at least 1 day and possible 2 days.
tomshobby

Pressure is the same in both ends of the cylinder - same bore and they are hydraulically balanced inside. The reservoir is split in unequal proportions - big side feeds the front brakes, since they use more fluid as lining wears, having bigger pistons. So, pipes attach according to reservoir sizes.
If there are two sizes of tube fittings, it should be obvious at the master. The size difference may or may not persist at the PDWA block. Big ones are 7/16-20, small ones are 3/8-24, but both tubes are 3/16. The clutch tube is the only different sized pipe - 1/4".

FRM
FR Millmore

"The reservoir is split in unequal proportions - big side feeds the front brakes, since they use more fluid as lining wears, having bigger pistons. So, pipes attach according to reservoir sizes."

Thanks,
Tom
tomshobby

This thread was discussed on 17/02/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.