will a master cylnder work for disk/drum brakes?

hey guys i was just wondering if a master cylnder would work for disc brakes in front and drums in the back for a 55 chevy truck
i would really appreciate the advice thank you
kujo

 

Uh, yes, if you get a MC for a system with front disks and rear drums, and the proportioning valve that goes with it. Did you mean the stock MC? You'd be better off with a MC intended for disk/drum, as a drum system keeps a little pressure on the shoes with a residual valve. It'll hang up the pads on the front, and you'll be parked. Ask me how I know this...

 

you need a duel master cylinder and a disk to drum proportioning valve. all of the brake system componets need to be compatable to work properly.

 

I just went through this in agonizing detail on my own truck. Wanted to make sure I knew what was the right way to go and what was safe. Its amazing how many people sell this stuff and don't really understand how it all works in the system.

You need a dual reservior master cylinder. This will have a large reservior for the front discs and a smaller reservoir for the rear drums. They generally have a larger piston for the discs since they take more fluid to actuate. The other benefit of the dual system is redundancy. if you have a leak in, lets say the rear lines, the front system (the discs) will still function. Your pedal will travel much further, but it will still stop. It is important that your drums are always in good adjustment or in the case of a front system loss, your pedal might hit the floor before it can push enough fluid to actuate the rears. In addition you will need residual pressure valves front and rear. 2 PSI in the front and 10 PSI for the rear. Many dual reservoir MC's have a 10PSI residual pressure valve built in for the rear so check that out to be sure.

If you are installing a new system, get whats called a "Combination valve". you can get these from piratejacks.com.

A combination valve does 3 things additional things. First is a "hold off" function. this allows the drums to engage before the discs do. this will go a long way towards stopping the nose-dive effect that is common in front disc systems.

Second in the conbination valve is a proportioning valve. this reduces overall pressure to the rear to stop the rear wheels from locking up during a heavy braking situation.

Third in the combo valve is a pressure differential switch that lets you know if one of your systems has lost pressure. You can run an indicator light off the combo valve to notify you in the event of a pressure loss.

this article explains it all in great detail:

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/master-brake1.htm
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So, get the dual MC, get the appropriate residual pressure valves and then get a combo valve and you will be all set.

Throw an E-brake in the mix and really impress the ladies.

 

call master power or eci and write them a check. pay extra for a prop valve. you'll be glad you did.

 

nicefloor thank you for all the info and ill try and put a pic of what i have im pretty sure its a dual resiviour MC. and no im not gona use the stock MC. i have this one i was thinking about geting a combo valve. i just wasnt sure if it would work for disc and drum brakes

 

The standard MC used in the hot rod industry for disc/drum is a copy of the 1968 Corvette unit. Like has been said the larger resevour (front) goes to the front disc brakes and the smaller on to the rear drums. A pressure residual valves of the proper value should be used in the system.
If you ever get a chance to talk to Ralph Lisena, owner fo ECI bend his ear about brakes, I doubt you will stump him he is a master.

Frank

 

Early disc drum Mustang will work good.

 

fab 32 thanks man i will but whats ECI ? and thanks to every one for all the help this is exactly why i love this site
kujo

 

Most masters bolt on with the same pattern, you can buy one for a disc-drum combo either power or manual right at a parts store that will do the job. As noted, you need a proportioning valve with it.

 

so ur saying that if the MC i have right now isnt the disc drum i could probly get one that is disc drum and it probally bolt right up ?

 

It all depends on your car/truck. Just because it will bolt up, doesn't mean that there will be the correct pressure bias front to back for your setup. Make sure get a master cylinder for a similar vehicle and a proportioning valve.

 

try here http://www.classicperform.com/

i'm not too sure if anything is a direct bolt on, most likely you have to modify or make something.

 

thanks man will do and thanks everyone been big help
kujo