ok i know this sounds stupid but i am swapping from a drum rear to a disk rear and i heard that unless i changes the prop valve my brakes will be weak, however i have also heard that the drums use more pressure. so wouldnt not switching actually make the brakes really touchy?
i tried doing a search but the search feature is all messed up

thanks

anybody?

Some members report that their brakes function fine without the proportioning valve swap. Still, I'd suggest changing for the best results.

JamesC

Drum brakes use pressure, and disk brakes use volume. (or vice versa, I can't remeber right this second) So, if you don't change the prop valve, the rear brakes will work. But unless you change to a disk prop valve, the swap to disk will not increase the brake performance. So ya, might as well change the prop valve while you have the brake system open. Plus, it's easy to do.

I changed from rear drums to a PBR set-up from a GTA 3 or 4 years back. I had the same questions at that time and decided to see what wousd happen if I didn't change the prop valve. The brakes seem to work fine no leaks, pedal seems firm, over-all braking feels good. Under hard braking front and rear rotors heat up pretty evenly. Been driving 3 to 4K a year since with no problems.

"Seem" is the key word. It would be interesting to hear from someone who drove without changing the valve for several months and who then swapped in the disc valve. At any rate, the valve has to be different for a reason.

JamesC

Like I said earlier, ya, it will work. But it's just another half-assed job if you asked me. The prop valve is easy to change and not that expensive. No real reason not to change it.

If you gonna do a job, why not do it right. And do it while you have the brake system opened.

Seems to me, the whole reason to upgrade to discs is for the better performance. Which your not getting the FULL performance of the disc brakes unless you put the correct prop valve in.


James, my buddy did keep the drum prop valve on for at least a year or so on his 91 RS with 1LE rear disks. Then he installed the disk prop valve (which he had the whole time, just never installed in), he immediately noticed the difference. Hense the reason, when I swapped in rear discs, I did the disc prop valve at the same time.

kris you make a good point. i went ahead and bought one the other day. seems stupid to spend all this time traking down a disk rear just to half *** the instalation

I couldn't agree more. So noted here:

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

OK you convinced me. As soon as the salt is off the roads and the car comes out of storage a correct prop. valve is going in. Do you recommend GM or are the parts store ones just as good?

GM. Ed Miller can hook you up.

JamesC