dual master cylinder for brakes--questions

[pdrnec]

Soo, the question remains, does the dual MC truly result in loss of front or rear brakes, instead of both? Looks like that has not been at least two of us' experience.

And so it remains. I have a new dual MC in the box - guess I'll swap 'em put and see what it does. Just need to figure out how to test what happens if I lose a brake line again...

[SScopelli]

Tech post

http://www.studebaker-info.org/tech/brakes/36237T/36237T.html

Looks like this was adapted to have a remote Reservoir fill up in the engine compartment..

[Dan Timberlake]

Here is an old discussion about dual circuit master cylinders mostly by folks with a variety of technical back grounds.

http://www.eng-tips.com/viewthread.cfm?qid=129906

I think the explanation that the "other" circuit was already faulty makes sense. Mostly possible with drums at one end that are very out of adjustment, which would require a couple of pedal pumps to come into play. (Discs are always self adjusting, bit if one circuit was not properly bled it could be pretty eneffective). With a single system one or two badly adjusted drums would likely show up as longer pedal travel pretty early on.

Has anyone had a dual system on a 4 wheel disk brake car lose all braking with a sudden hydraulic problem in one circuit ?

[pdrnec]

Yes. Mine is a 4 wheel disk brake car. Turner conversion.

[pdrnec]

Found the answer here, definitely a problem with my system.

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/master-brake1.htm

[JoeHall]

Here is an old discussion about dual circuit master cylinders mostly by folks with a variety of technical back grounds.

http://www.eng-tips.com/viewthread.cfm?qid=129906

I think the explanation that the "other" circuit was already faulty makes sense. Mostly possible with drums at one end that are very out of adjustment, which would require a couple of pedal pumps to come into play. (Discs are always self adjusting, bit if one circuit was not properly bled it could be pretty eneffective). With a single system one or two badly adjusted drums would likely show up as longer pedal travel pretty early on.

Has anyone had a dual system on a 4 wheel disk brake car lose all braking with a sudden hydraulic problem in one circuit ?

What I got from that link was a few folks citing real world experiences, of total failure, and several others speculating. The real world experiences matched mine. I am unsure whether a few rapid pumps of the pedal may have produced enough brakes in the rear system to have stopped the car. Brake failure is one of those situations where things happen real fast, and when totally unexpected, so there is a bit of lag time between sensory nerve signals to the brain and motor nerve response. In other words, hard to react quickly enough to avoid a catastrophe. Still, in theory everything should be ok... The Ralph Nader reference was interesting.

[r1lark]

Found the answer here, definitely a problem with my system.

http://auto.howstuffworks.com/auto-p...ter-brake1.htm

Pat, I looked at the link you provided, but still not sure.....what is the answer??

[alpayed]

I wrote an article about dual master cylinders some time ago and it is on Bob's site here--http://www.studebaker-info.org/tech/atyler/atbrakes/stude_brakes_long.pdf
It explains the function and operation of them. It may be of some help in understanding how they work and why you cant just use any dual master cylinder even if the bore is correct.
The primary and secondary strokes have to be matched to the volume of fluid consumed by the front and rear cylinders/calipers.
If you have fitted a dual master you can test it as follows.
Bleed all wheels and ensure you have a good pedal.
Put a length of hose on one of the front bleeders and run it into a container.-- open the bleeder.
Push the pedal and it should go about 2/3 the way to the floor and the rear brakes should apply.
If it does not apply the rear brakes then the strokes are incorrect.
Re bleed the fronts to achieve a good pedal and repeat the process opening the rear bleeder.
The pedal should should go about 2/3 the way to the floor and the front brakes should apply.
If not you have a problem.
Hope this helps

Allan

[DEEPNHOCK]

The street rod crowd vendors makes several remote fill master cylinder caps that you could install.
Then hide the reservoir behind the battery, or something like that.



Don't wring your hands on a good safety update.
Just do it and drive in comfort.
Jeff

[JoeHall]

I wrote an article about dual master cylinders some time ago and it is on Bob's site here--http://www.studebaker-info.org/tech/atyler/atbrakes/stude_brakes_long.pdf
It explains the function and operation of them. It may be of some help in understanding how they work and why you cant just use any dual master cylinder even if the bore is correct.
The primary and secondary strokes have to be matched to the volume of fluid consumed by the front and rear cylinders/calipers.
If you have fitted a dual master you can test it as follows.
Bleed all wheels and ensure you have a good pedal.
Put a length of hose on one of the front bleeders and run it into a container.-- open the bleeder.
Push the pedal and it should go about 2/3 the way to the floor and the rear brakes should apply.
If it does not apply the rear brakes then the strokes are incorrect.
Re bleed the fronts to achieve a good pedal and repeat the process opening the rear bleeder.
The pedal should should go about 2/3 the way to the floor and the front brakes should apply.
If not you have a problem.
Hope this helps

Allan

This makes sense, and aligns with the design theory. The MC I have always used is the one recommended by Turner. It fits AMCs, Jeeps, and 1966 Studes. I have always thought the 1" bore was barely adequate with disc brakes, but it works great under all conditions, except line failure as described above, at least in mine and the OP's cases.
I do not think it happened to mine due to the rear brakes being out of adjustment. With Hawks, I learned long ago that, once the emergency brake is adjusted properly, I can use it as a "gauge" to tell me when the rears are in need of adjustment. I can also tell by brake pedal travel. I throw away the automatic adjusters on every Stude because they don't work well enough to suit me, so I try not to leave anything to chance.
Anyone with a dual MC can "test the theory" easily by, as you said, cracking a bleeder valve on either end and then pushing the pedal. It may be interesting to hear others' results.