Stovebolt.com Forums The Shop Area Driveline Double Master Cylinder

My main concern when one of these discussions comes up is that someone will buy a bunch of mismatched parts and end up with a system that's actually dangerous, instead of being "safer" than what was there originally. A minor miscalculation where the diameter or pedal stroke is concerned could result in brakes that either require too long a pedal stroke to get all the brakes applied, or a very short stroke that requires a massive amount of pedal effort to get the vehicle stopped. Either situation could get exciting, or worse, particularly if there's a failure of half the system. I seriously doubt that many, if any people on this site actually understand how the system becomes redundant in case of the failure they're so afraid of. Do they realize that the brake pedal will go to within a couple of inches of the floor before they get any one-axle braking at all, and pumping the pedal won't help?
Jerry

I plan to do one of the following with purchases from a supplier such as "LMC Truck":

1) Install an OEM-style single reservoir system with the appropriate stainless steel brake lines with existing original wheel cylinders

Or

2) install a dual reservoir with booster system with the appropriate stainless steel brake lines with existing original wheel cyllnders

Wouldn't either approach be sound?

Thanks

If you go with the boosted dual piston MC, be sure that it has the same diameter bore and volume displacement as the original part. Most vendors will have no clue about either one of those questions, so you'll probably need to do your own research on the subject.
Jerry

Mark's response brings out some good points.

"In both cases I just used combinations of parts that were similar or identical to those in later vehicles that originally had the dual system."
"The proportioning valve needs to either be adjustable or one that is from a similar weight vehicle with a similar brake system."

https://lugnutz65chevystepside.weeb...aster-cylinder-brakes-1963-1966-c10.html

I have known several people who still have single master cylinders on there classic cars with front disc brakes and all have said they have never had any problems stopping there cars.

Don’t think so………disc brakes run on about twice the pressure as drums. So single master on disc/drum vehicle is not going to work.
Stock OE master with disc brakes is NOT an upgrade.


Power brake dual master cylinder disc kits are not mystery or new concept. Q

I'd love to see some pressure gauge readings to support that claim. Getting different fluid pressures to the front and rear of a brake system would require a master cylinder with different diameter pistons operating the front and rear brakes. Getting different line pressures from a master cylinder with a single bore diameter would require repealing several laws of physics, with or without a power booster.
Jerry

Maybe he meant volume.

Had a pressure gauges permanently connected to a training car……just for the non believers. Will see if I can find a the photos and videos will post them
Full lock up on power disc often exceed 1000psi


In the mean time maybe duckduckgo will work:

For starters, the two brake systems work under different fluid pressures utilizing different master cylinder bore sizes (learn about master cylinder bore size and its effect on braking in this guide. Drum brakes use approximately 400 psi to apply, whereas disc brakes use 900 psi and higher to apply.

The proportioning valve or combination valve will limit the rear brake pressure and allow the front disc pressure to increase as needed. Thats the way to get the different pressures from one master cylinder.

Mark