Brake proportioning valve question...

Hello all. I have searched this topic and I haven't found an answer to my situation.I have a 66 I upgraded to 11" brakes all around. I got a good deal on a pedal/power brake booster setup for it off of a 89 Wrangler. The master cylinder that came with it is probably for front disks (safe assumption). I assume I need a proportioning valve for the rear brakes???? Like a wilwwod adjustable.What about the front???? None needed there right????How do I set this up.Any advice will be appreciated.

Thanks, Steve

 

So this master cylinder is only for the front? Does it have one or two chambers? I guess I never payed attention to the newer MC's I have a 2 chamber one on my 71' although it is manual brakes. I am curious about this also. Oh I almost forgot I have a propotioning valve on my JEEP to adjust the power of the brakes.

 

The M/C is for both front and rear. It's a regular 2 chamber type.....

 

If the MC you are thinking of using was for a disc front/ drum rear it will have a residual pressure valve of 2lbs for the discs. That's your first obstacle. Drum brakes need a 10lb residual valve to operate correctly. You may be able to remove the residual valve from the MC and install the proper 10lb valve inline. They can be had from Summit Racing or Wilwood. You shouldn't need a proportioning valve for 4 wheel drum brakes. If you find that you do need one (though I doubt you will) PM me as I just took one out of my Jeep when I converted to 4 wheel discs.

 

This unit came with a proportioning valve. Would the 2 lb valve be in there????Or are they in the M/C????

 

Typically, they are in the MC, usually located inside the orofice that the brake line screws into. On the stock MC's I have dealt with, you can remove the valve with a sheet metal screw by threadng it in and pulling it out.

 

I think you wont need a proportional valve because you have different wheel brake cylinder sizes in the brakes. This is how the jeep braking power is proportioned with 4 wheel drums. Also with the 2 lb valve.. I dont see why you need to remove the 2 lb, if you were to install a 10 lb inline ? So, I would think just a 10lb inline valve is all you need.

 

Because then you have 12 lb residual line pressure which can hold the shoes applied or cause them to retract too slowly whereas 10 lbs. won't.

 

Residual pressure valves should not have come on an 89 Wrangler at least not for the front disks. They are generally only usd on vehicles with the disk brakes lower than the MC as they would have been on the 71 or older, but after that all MC were mounted higher than the brakes making the RPV's obsolete for the disks. The proportioning valve is only used to adjust the bias from front to rear of the brakes so that more of your stopping power is from the front brakes as they should be. The older models of jeeps used different sized wheel cylinders front to back to in effect do the same thing with out the proportioning valve. Check to see if the wheel cylinders are the same front to back. If they are, then the proportioning valve goes in the system to in effect choke down the rear brakes so that more fluid is fed to the fronts.

 

DOH! Must've been the paint stripping fumes from the house! Good catch!

 

I'm making a similar modification to my '71, but doing it in 2 stages (hanging pedals & firewall manual M/C first, then Dana 30 w/power disks second). Read everything at this site and go from there - don't let the math bog you down though.

This is good stuff:
http://www.pirate4x4.com/tech/billavista/Brakes/

 

Thanks David. Tons of great info.....