brake issues

[hardhead]

Took our 66 for the first ride from a 3yr rebuild and the right rear is locking up under moderate braking. Everything is new except for the proportioning valve, new hard lines, rubber lines WC, MC, Calipers and hard lines. We used 72 disc brakes and a used 72 prop valve, S10 8" booster and MC. I'm pretty sure it's plumbed up right. My son took the plug out of the little shuttle valve and said it was spring loaded and he could push it with his finger. I heard talk about a button on some of them but ours doesn't have one. Any ideas? We are hoping to get it registered and hit cruisin the coast in MS in a couple of weeks.

[hardhead]

For some reason the proportioning valve is blocking off fluid to the front brakes. I've tried opening the bleeder to the rear and stomping the pedal to try and get it to center back up and no luck. Put another valve on and same thing. Anyone had a problem like this? There has to be a brake guru on this site that has some input.

[scum1]

I am having similar types of issues with my truck. Rear brakes (not sure which wheel) locking up under moderate braking power. I assumed it was associated with the proportioning valve somehow. I cannot seem to figure out a way to narrow down the problem. Do you have a brake warning light hooked up to the valve. If not, you should try hooking up a test light to the battery and connecting it to the pin to check for a ground, which would indicate an offset valve in your case. Mine does not, yet it still seems to have an incorrect pressure distribution to the front/rear.

anyone have any suggestions for us?

[PGSigns]

Try looking at the adjustment between the two sides on the brake shoes. Mine did it some early on and I readjusted them. Now that they have had time to seat under hard braking they both will lock and a little more pedal they all lock. I just attribute it to the weight balance of the truck. Under stiff braking the back gets pretty light.
Jimmy

[lolife99]

Are you sure sure you are getting full stroke out of your M/C?
You may need to lengthen your brake pedal pushrod.

[oldman3]

Originally Posted by PGSigns

Try looking at the adjustment between the two sides on the brake shoes. Mine did it some early on and I readjusted them. Now that they have had time to seat under hard braking they both will lock and a little more pedal they all lock. I just attribute it to the weight balance of the truck. Under stiff braking the back gets pretty light.
Jimmy

Originally Posted by lolife99

Are you sure sure you are getting full stroke out of your M/C?
You may need to lengthen your brake pedal pushrod.

I'm no brake guys, but I also think one of these above may be your problem. With that said, for anyone else who make look at this thread, here is the bleed tool to keep you valve centered. I got mine thru Performance Online. Printing doesn't show up to good, sorry...Jim

[scum1]

Originally Posted by PGSigns

Try looking at the adjustment between the two sides on the brake shoes. Mine did it some early on and I readjusted them. Now that they have had time to seat under hard braking they both will lock and a little more pedal they all lock. I just attribute it to the weight balance of the truck. Under stiff braking the back gets pretty light.
Jimmy

are you referring to the self adjusting "star adjuster"..saying to check that both wheels have been adjusted the same?

I kinda always assumed that because it does have such a light rear end that it would eventually have to lock up at a certain speed. i just read a whole bunch of articles about brake bias, and combination valves etc..and it got me testing my own truck, and thats where i was able to continuously lock up the rear, when i feel like maybe it could be out of adjustment somehow.