what size master cylinder ?

[misfit41]

I am moving the pedal box on my SV to the floor so I will need to use remore style master cylinders,with GM front calipers and ford SVO in the rear,what size bores should I use ? any one have experience on this one ?
thanks,,Tk

[rdorman]

Here I go again!

Assumption, you have a single, tandom, master cylinder and you are going to a dual master cylinder/balance bar setup up, the new peddles will have the same mechanical advantage, you are not changing to or from a power brake system, the brakes balance you have now is good and the proportioning valve does not reduce initial pressure and last but not least you are happy with the peddle effort you have....... phew! Is that correct? Any one of these changes the answer.

I will do some more reading this evening if time allows, but here goes nothing!

Going to dual master cylinders from single halves the amount of pressure the master cylinder sees from your foot. Sooooooooo, if your master cylinder now is a 1" bore you will need a front master cylinder of half the area. Not diameter, area. .70 master cylinder being about 2% small and a .75 being about 13% large (less and more relative peddle pressure). Be aware that the master cylinder you have may have two sizes in it, one for front and one for rear.

Now is the time to address any issues related to the first paragraph in here. Choose wisely grasshopper.

I have all the math at home.

Rick

[misfit41]

Hi Ron,and thanks for the reply,I am sorry for not being more clear,,
I already have the balance bar dual cylinder set up,but will need to change them to remote resevoir style,I previously had front mustang disc and drum rear brakes,but am going to the front GM calipers and the SVO 9" inch ford set up on the rear,will staying with the same size bores I have work ok considering the rear disc ? or do I need to use something different ?
thanks again,,Tk

[rdorman]

In my opinion, you are starting from scratch.

If you can get me:
- tire diameter
- front and rear weights
- wheelbase
- peddle ratio
- number and diameter of caliper pistons
- coeficient of friction of pads (look at the edge codes and/or contact manufacturer or pick a new pad to buy of a know value and use them)
- mounting of calipers (fixed,sliding)
- disk diameters
- type of tires you will run

..... then I will be able to get you in the ball park. Close enough that the balance bar should take care of the rest.

Rick

[misfit41]

wow,,
That all sounds a bit complicated when there are only maybe 2 choices as to the bore diameters to choose from,7/8th and 3/4 if I remember correctly,I think i will just use the size I have now and adjust from there.
thanks for the look,,Tim

[rdorman]

You never know, you may get lucky! But that is certainly one approach, it just may cost more. Tilton has at LEAST seven different sizes available that I know of.

Some tips on the approach you are taking.

Take the time to adjust your balance using the balance bar. Then, if the balance bar needs to be set to far off center, change a master cylinder size to get it centered. Which one you change depends on other things. For instance, if you can not lock all four tires no matter how hard you push or you feel the peddle effort is to high, make the master cylinder that the balance bar is adjusted towards smaller. If the reverse is true make the opposite one larger.

I didn't even ask you everything I need to know to reduce the margin of error! I would also need items such as center of gravity height, aero dynamic loads, etc. But, I make some reasonable assumptions and they work fairly well.

Be sure you don't have the residual presure valve in teh rear line for the drums. I could be hidden in the proportioning valve, etc if you have one in the system.

Rick

[misfit41]

thanks Rick,
I will print your replys for reference and go from there,if I get stumped I may email you ,,I appreciate the help..Tim

[Rick Parker]

Tk...........you have mail!

Rick