Rear Disc Swap

[1badchevy]

Hello everyone. Im new here and would like some knowledge imparted on me. I am doing a posi disc rear swap and was wondering what is the best way to go about modifying the proportioning valve for the brakes. There is no point in having rear discs if they barely engage. All info is much appreciated, thanks

 

[pontiacgp]

most install an adjustable brake bias valve. You can't use a proportional valve that was used for drum brakes. It has a residual valve of 10 lbs and a disk brake only uses a 3 lbs residual valve. You can use the adjustable valve and install the residual valves in the lines

 

[84GP455]

I swapped my 7.5 rear for a 8.5 with discs 2 years ago and I got a 50/50 proportioning valve and it works great. The factory prop valve for rear drums is like 70/30 meaning the front gets about 70% pressure and the back 30%. The 50/50 means equal pressure because the back requires more pressure now to get to the rear to work the calipers. I tried an adjustable prop valve like Pontiacgp said but it didn't work for me, it only adjusts the pressure that's already going to the back brakes, it doesn't add pressure, and I didn't have enough pressure going to the rear with the stock prop valve.

 

[1badchevy]

thanks yall. i think im gonna go w/ the 50/50 valve, do you remember where you got it from? i was also told that i could bypass the plug all together with a bolt in its place.

 

[84GP455]

I forget where i got it from but I think it was from one of this sites advertisers like GBody parts or gbodywarehouse but I wouldnt bypass anything that has to do with the brakes!

 

[84GP455]

here's where i got it http://www.inlinetube.com/Prop%20Valves/PR-101.htm kinda expensive but they all are!

 

[pontiacgp]

a 50/50 proportioning valve is usually used with an adjustable brake bias for the rears. There is a reason that more pressure is sent to the front. The front do more breaking than the back and too much rear brakes will send the rear around in a corner, and do it quicker in the rain The only instances I have heard of that more rear brake than front is needed is on drag cars using the skinny front tires

 

[1badchevy]

thanks alot. did you hit any other issues along the way? how do you feel about the swap now? was it worth it?, thanks

 

[1badchevy]

a 50/50 proportioning valve is usually used with an adjustable brake bias for the rears. There is a reason that more pressure is sent to the front. The front do more breaking than the back and too much rear brakes will send the rear around in a corner, and do it quicker in the rain The only instances I have heard of that more rear brake than front is needed is on drag cars using the skinny front tires

i am pretty sure stock had a 90/10 bias. do you think 50/50 is too much to the rear, or should it be ok?

 

[85GPLef41]

I was going to try to use this proportioning valve. They take your stock valve and modify it and send it back. I just recently installed my C6 calipers using LS1 rotors and brackets and need to address this issue. Anybody using it?
http://www.flynbye.com/catalog/i67.html