The Stovebolt Site Forums The Shop Area Engine Shop Dual vs Single master cylinder

Since I'm getting ready to rebuild my entire brake system, is it really worth the extra $50+ to go with a dual cylinder vs staying with a single. What makes them different in operation? No, I'm not going discs on the front.

I put a dual master onto my 55 1st series purely as a safety issue. If a line breaks or a wheel cylinder seal blows out on a single master system you stand to loose all braking power. On a dual system the front and back brakes are independent so if a line blows out you will only loose the front or the rear brakes but not both. Whether or not it is worth the extra $50 bucks is purely a personal issue of how important you believe that issue is (in my opinion) but you should also take into account how fast you plan to drive the truck, additional weight you put onto the truck, etc.... Hope this helps.

As someone who has survived a line blow out on a single cylinder system (at freeway speed) I say spend the $50 extra if you are going to replace the master anyway.

Imagine going down a hill and only having your mechanical emergency brake to stop yourself...

New front bumper, steel: $100
Junkyard right front fender: $250 delivered
Miscellaneouse bolts, brackets, and retainers: ~$150
New dual master/power booster/lines&fittings: $400

Not killing a family in a RAV4 who pulled in front of me when I was doing 45 mph: Priceless

How does that $50 sound now?
(I suppose I'm gonna get a letter from the MasterCard attorneys. :p )

What Hedgehog said.

cmayna, Simply put, A single master cylinder puts all your eggs in one basket. If the basket fails, you are in trouble.. A dual master gives you room for error. If a line or a wheel cylinder fails, you have more eggs to help you stop.

Aren't you the guy that is re-painting his truck ? If you have money for paint you should have money for a proper braking system.

Spend the extra cash and make sure you don't kill yourself or anyone else..

ok ok ok!

Thanks guys

ok, now that i can drive hiway speeds, what kind of dual master cylinder will work on my '54 3800 panel(gvw 8800)on 7.50x17's and what all has tobe done to install it? I'm going to keep the old brake shoes at this time. Hey Hedge, what kind are you using?

tony'n weatherford (at work) :rolleyes:

The kit I ordered is a GM dual resevoir master with a 7" booster attached, it came with a heavy steel bracket to push the whole assembly away from the framerail (room for the booster) and a linkage offset rod to connect to the stock pedal. I believe it was made by MP , but I can't remember which vendor took my money. The installation instructions and receipts were lost in a move a couple years ago.

For a halfton pickup, you don't really need a booster; I went with one because of the weight of a loaded panel truck. This put the resevoir next to the transmission cover, and the M/C fill hole in the floor is now useless. You can sidestep this issue with a remote resevoir on the firewall or perhaps the non-booster duals line up better with the stock floor hole. :confused:

When you go to a dual-circuit master, you must bend new line. The original configuration has three wheels on one line and the left front on it's own feed; you will never get balanced braking unless you put the fronts on one line, and the rears on the other. I spent a day under the truck with a tapemeasure, then went to NAPA for various lengths of line with flares and fittings attached. Taking my time and doublechecking each fitting, the whole brake system took a day to install.

The new M/C had 3-lb. residual pressure valves built in, but for drum brakes you will want 10-lb. valves (MP sells them for $26/each). This will take the "mush" out of the pedal and give you a quicker brake response.

Now I just need to figure out how to keep RAV4's off the grille. :rolleyes:

If your staying dum all around, a dual master cylinder from a '70 Chevy Nova will work.
It has equal reservors, and 1"bore size. You'll need to fabricate your own mounting mounting.This can be made by reworking the original bracket.

ok whitelighting, you're saying a master cylinder from a '70 nova will work on a '54 1 ton, 137" wheel base PANEL TRUCK ?
thanks again,

tony'n weatherford(at work still) :rolleyes:

I just did this on my 1 ton. I used the Chevy duty bracket along with a M/C from a 66-74 Impala. Works great. Also those residual pressure valves, you can get them at summitracing.com for only 16.95. Although I decided to see what it was like without them first. So far so good.

I read an article in a recent Street Rodder magazine that has me intrigued. They used a master cylinder in the stock location using the stock pedal, which was plumbed to a slave cylinder that operated an ordinary vacuum booster/dual master cylinder in a remote location (under the passenger running board). In the article they used a dual master cylinder in the stock location, which required the use of two slave cylinders tied together to push the rod in on the booster.

Using the dual master cylinder in the stock location to run two slave cylinders seems a little redundant to me. There are LOTS of medium duty trucks with hydraulic brakes out there that run single master cylinder and a hydrovac. The hydrovac then boosts the line pressure and sends the brake fluid to all braking wheels. There is no 'dual system' on these trucks.

I think there are definite safety atvantages to running a dual system, as have been explained above. I have been seriously considering using a new stock master cylinder to operate a slave cylinder that would operate a booster/dual master cylinder in a remote (easier to access for service) location. I need to do some more research on this idea, but I would like your input on this idea.

I have a couple of stovebolts that see regular use on the road. My '49 is getting all new wheel cylinders, rebuilt master cylinder and all new stainless lines. It is essentially stock except for the '57 235 in it. The probability of blowing a wheel cylinder and or hose and or tube with everything new is something that has to be weighed against whatever mods you do to the rig that detract from you desire to stay stock.

For me with this truck - with all new components the probability of catastrophic failure is pretty much nada. I have done due diligence in removing risk by replacing everything . . . good enough for me.

Ken, what bore diameter master cylinder do you need?

Mech - I already have all the parts and pieces. I am just waiting for the Fed-X ground package with all the tubing.

The RPV's are only nessary if your master has no check valve!

If you get the master bore size right you just don't need a power booster

Some years ago I ran a Lola T294 .....this thing had four wheel disc brakes and two dinkey masters and no booster!! It would haul in from close to 200
But it didn't carry much

No matter what kindda setup you use make sure everything is in good condition.

If your running 'airquip' please use only steel
NO BRASS NO ALLOY

If your going with the original master cylinder ect.... Use Silcone brake fluid, it absorbs less water the the regular stuff.

Careful on that recommendation, I don't recall if the silicone brake fluid may be compatible with all the old rubber seals. Primarily the application for that fluid is racing and high temps, the old stuff should be sufficient...

...IF YOU REGULARLY REPLACE YOUR FLUID! That's right, once a year drain and replace with new fluid. That's a step many folks forget for keeping the brake system rust free.

-Boyo

Craig, replace all of your brake lines...it's a piece of cake. It's easier to bend-up your own(and 1/4 the cost) than trying to fit in prebent lines($$). You can buy the lines with the fittings on there already from Napa, Kragen, etc. I just followed the basic routes and used the rubber-coated line clamps where I thought it was good. One of my stock lines was cracked where it runs down the frame (hidden) and decided to let go while backing the truck off the lift at the muffler shop. GLAD there was a good sized parking lot behind me. Don't let a shop do it for you....piece of cake.

OH yea...JMO...I ran silicone fluid in my old beemer and it screwed-up every rubber piece it was in contact with. Swelled the rubber up and they had to be replaced. I don't use it.

Oh yeah, and keep those bleeders tight...
:rolleyes: