[Damo]

This is a little sidetrack to my Vit master cylinder thread. Clicky.

Acording to the interwebs, a vehicle fitted with drum brakes has a residual pressure valve, usually in the master cylinder, which maintains pressure on the seals in the wheel cylinders.

Does anyone know if the Sierra has one of these? Is it in the master cylinder? Or is it in the proportioning valve block thingy toward the back of the vehicle?

Who's running rear discs and did you have to do anything about the residual pressure valve. Apparantly it should be pretty obvious if you have one and need to remove it, as you converted rear disks will lock on after one or two applications.

I just found this link which has a little more info Wilwood RPVs

[royce]

only 4 wheel disc zook I have had was my 1 litre which was originally 4 wheel drum and still had the 4 wheel drum master cylinder and no booster

Rally cars run little inline valves to keep some pressure on the calipers to stop the rough roads knocking the pads back and making the pedal drop, jsut to confuse you more

[Damo]

royce wrote:

only 4 wheel disc zook I have had was my 1 litre which was originally 4 wheel drum and still had the 4 wheel drum master cylinder and no booster

Rally cars run little inline valves to keep some pressure on the calipers to stop the rough roads knocking the pads back and making the pedal drop, jsut to confuse you more

Yeah on that Wilwood link it explains about the 2PSI and 10PSI valves.

I will keep doing some digging on this but if I find nothing i'm just going to put the brakes together and see how it goes

I do have a chassis which i'm pretty sure has that valve block on it, i'll have a closer look at that I think.

[joeblow]

sierras that have front factory discs do not have a residual valve in either of the ports, only vehicles that had 4 wheel drums had them.