Residual brake valve

[midnight sun]

Hope this doesent post twice.  I did it once and it never showed up anywhere.

I am getting ready to swap out my Wilwood Residual brake valves for some SSBS ones.  Most all of the literature I have read says place the rear valve as close as possible to the master and before the proportional valve. SSBS instructions say to place the valve beyond (I assume that measns after) the proportional valve.  Why would it make any difference?

Any input/explanation would be appreciated.

Later

[enjenjo]

No Idea. FWIW I always install them between the master cylinder, and the combo valve, but thinking about it, it might be better downstream, after the combo valve.

My thinking is this. A combo valve incorporates a shuttle valve that will shut of one end or the other if a line breaks, and you lose pressure. If you have a 2 psi valve in one line, and a 10 psi valve in the other, upstream of the combo valve, there could be a pressure differential, and it is remotely possible that the shuttle valve could be activated, shutting off one end or the other.

[Bruce Dorsi]

Jack, I have read several times that the placement of the RPV can be either before OR after the prop valve, and that it does not affect the operation of either component.

I realize reading it somewhere does not make it "gospel," but for lack of definitive explanation, I'm inclined to believe that statement.

A phone call to SSBC (1-800-448-7722) could provide an answer to why they state a preference for its location.  ....They also have some tech info on their site at:
http://www.ssbrakes.com
but I don't see an answer to your question there.  

Out of curiosity, are you replacing the Wilwood RPV's because they failed, or is this a precautionary measure?

[midnight sun]

Out of curiosity, are you replacing the Wilwood RPV's because they failed, or is this a precautionary measure?[/quote]

I am having trouble with my braking system.  It works fine if I dont hook up the vacuum booster but as soon as I do I lose most of the pedal.  After getting some input from those who have been there, the consensus of opinion is that Wilwood doesent make very reliable residual valves.  Several folks have said they have never had problems with SSBS so thats why I am replacing them.  Thats not to say it will cure the problem but its a place to start.  If that doesent do it, I guess I need to look into replacing the booster.  Although new, I have also been told they can be bad.

[Dave]

Out of curiosity, are you replacing the Wilwood RPV's because they failed, or is this a precautionary measure?

I am having trouble with my braking system.  It works fine if I dont hook up the vacuum booster but as soon as I do I lose most of the pedal.  After getting some input from those who have been there, the consensus of opinion is that Wilwood doesent make very reliable residual valves.  Several folks have said they have never had problems with SSBS so thats why I am replacing them.  Thats not to say it will cure the problem but its a place to start.  If that doesent do it, I guess I need to look into replacing the booster.  Although new, I have also been told they can be bad.[/quote]


I used wilwood on the 34 and also the 32.. They seem to be ok but i need to rebleed the brakes cause its pulling to the right when i hit the brakes. I did take the bleed screws out cause they were leaking but didnt bleed them again and thats prolly the problem.
Dave

[Kctom]

Out of curiosity, are you replacing the Wilwood RPV's because they failed, or is this a precautionary measure?

I am having trouble with my braking system.  It works fine if I dont hook up the vacuum booster but as soon as I do I lose most of the pedal.  After getting some input from those who have been there, the consensus of opinion is that Wilwood doesent make very reliable residual valves.  Several folks have said they have never had problems with SSBS so thats why I am replacing them.  Thats not to say it will cure the problem but its a place to start.  If that doesent do it, I guess I need to look into replacing the booster.  Although new, I have also been told they can be bad.[/quote]
Check you rod adjustment. I had the same problem and it was that. If you take the cap off the master cylinder and apply the brake , look at the fluid in the master cylinder. You should get a slight ripple in the fluid. This is the piston pushing past the return hole  and building pressure for the brakes. Instead of a ripple you shoot fluid up in the air the push rod is not adjusted right. This is what I was told to check on mine. Sure enough the fluid was shooting up in the air about 12". Just be sure you don't adjust so thge return hole is blocked. This may or may not help. It worked for me

[midnight sun]

Check you rod adjustment. I had the same problem and it was that. If you take the cap off the master cylinder and apply the brake , look at the fluid in the master cylinder. You should get a slight ripple in the fluid. This is the piston pushing past the return hole  and building pressure for the brakes. Instead of a ripple you shoot fluid up in the air the push rod is not adjusted right. This is what I was told to check on mine. Sure enough the fluid was shooting up in the air about 12". Just be sure you don't adjust so thge return hole is blocked. This may or may not help. It worked for me

Kc, I pulled off the top of the M/C and pushed the brake pedal and the fluid shot up in the air about 4-5".  The only adjustment I can see is where the clevis that connects the pedal to the rod, screws onto the rod. You can make the distance longer or shorter which in turn makes the brake pedal throw a little longer or a little shorter.  Either way it still shoots up in the air regardless of where I adjust it.  Is there another adjustment inside of the booster or M/C that Im missing?

[Jimc]

I had a problem with the vacuum booster on the 62. I do not have a rpv since I am running the original drum brakes front and rear.
I had installed a new master cyl and booster which I had purchased from NAPA
My problem was a hard pedal from the start.
I had to apply too  much foot pressure to affect a stop.
I mentioned this to the distributor and he replaced the booster, now the 62 brakes just fine.
A long story to say I do not believe your problem is the booster.

Jim

[Kctom]

Check you rod adjustment. I had the same problem and it was that. If you take the cap off the master cylinder and apply the brake , look at the fluid in the master cylinder. You should get a slight ripple in the fluid. This is the piston pushing past the return hole  and building pressure for the brakes. Instead of a ripple you shoot fluid up in the air the push rod is not adjusted right. This is what I was told to check on mine. Sure enough the fluid was shooting up in the air about 12". Just be sure you don't adjust so thge return hole is blocked. This may or may not help. It worked for me

Kc, I pulled off the top of the M/C and pushed the brake pedal and the fluid shot up in the air about 4-5".  The only adjustment I can see is where the clevis that connects the pedal to the rod, screws onto the rod. You can make the distance longer or shorter which in turn makes the brake pedal throw a little longer or a little shorter.  Either way it still shoots up in the air regardless of where I adjust it.  Is there another adjustment inside of the booster or M/C that Im missing?

The clevis is what I had to adjust. Soon as I got it right the petdal no longer fell down 3" when the vac. hose was attached. Don't know what that had to do with it , but cured the problem.

[Kctom]

Check you rod adjustment. I had the same problem and it was that. If you take the cap off the master cylinder and apply the brake , look at the fluid in the master cylinder. You should get a slight ripple in the fluid. This is the piston pushing past the return hole  and building pressure for the brakes. Instead of a ripple you shoot fluid up in the air the push rod is not adjusted right. This is what I was told to check on mine. Sure enough the fluid was shooting up in the air about 12". Just be sure you don't adjust so thge return hole is blocked. This may or may not help. It worked for me

Kc, I pulled off the top of the M/C and pushed the brake pedal and the fluid shot up in the air about 4-5".  The only adjustment I can see is where the clevis that connects the pedal to the rod, screws onto the rod. You can make the distance longer or shorter which in turn makes the brake pedal throw a little longer or a little shorter.  Either way it still shoots up in the air regardless of where I adjust it.  Is there another adjustment inside of the booster or M/C that Im missing?

The clevis is what I had to adjust. Soon as I got it right the petdal no longer fell down 3" when the vac. hose was attached. Don't know what that had to do with it , but cured the problem.

This is just a stab in the dark. Hook up the vac. tube to the booster, start the engine and adjust the pedal so that it is all the way up. Shut the engine down and take the top off the master cylinder and push on the pedal. See if you still get fluid shooting up in the air. If no fluid squirting up then the piston is too far past the return hole and brakes will not release. Try the same thing with the engine running and see what happens. Let me know.
TOM

[midnight sun]

This is just a stab in the dark. Hook up the vac. tube to the booster, start the engine and adjust the pedal so that it is all the way up. Shut the engine down and take the top off the master cylinder and push on the pedal. See if you still get fluid shooting up in the air. If no fluid squirting up then the piston is too far past the return hole and brakes will not release. Try the same thing with the engine running and see what happens. Let me know.
TOM

Tom,  Ill havta wait on firing up the engine.  Ive got the body off of the frame and am chopping it and doing some other body work.  I just thought I would get a head start and get some opinions on the brake problem.  Anyway I will archive your post and dig it out when the time comes.  Appreciate all of your assistance.

Thanks

Jack

[Skip]

FWIW, the FACTORY residual valve in a drum brake master cylinder is IN THE MASTER CYLINDER (well before the proportioning valve).

The only reason you'd want a 2-psi valve in the system is if the master cylinder is mounted under the floor, as its only function is to prevent the brake fluid from draining back, due to gravity, from the calipers.  
If the master is on the firewall, the ONLY residual valve you should have in the circuit is the one for DRUM brakes and that's normally right in the master cylinder.

[Anonymous]

If you have a disc-drum system on your car, you will need to have the right residual valves installed for the brakes to work like they are supposed to. It is true that old cars with all drum brakes had the valve built into their master cylinder, but that only works in stock systems.

The old drum brake cars did not have a proportioning valve since they used bigger diameter wheel cylinders in front than they did in back. This gave each axle the correct braking pressure.

Disc brakes need a proportioning valve to distribute pressure right when rear drums are used. Otherwise, you would lock up the rear wheels too easy. Race cars have adjustable proportioning valves to help set the ratio for each vehicle or condition.

You need residual valves no matter if you have your master cylinder under the floor or on the firewall. They keep a constant pressure in the lines behind the caliper or wheel cylinder and prevent a soft pedal or excessive travel after not using the brakes for a bit. They help insure that your drums react a little bit before your discs do to let them apply together, or else the disc brake would grab faster and the drums would have to catch up. I think it's recommended to have ten pound valves for disc and two or four pound valves for drum, if your master cylinder does NOT already have it built in.

When people swap brake boosters and pedals into hot rods, they sometimes don't get a full amount of travel in the rod that activates the brakes. They push the pedal all the way, but the rod does not move the piston in the master or activate the booster all the way. In some cases a simple adjustment is all it will take. Other times, a new rod or an adjustable one will be needed. Some pedals have one hole for manual brakes and another for power. The recommended pedal ratio is different for each.

Another thing I thought I should add is that the booster needs a good vacuum signal to work. And a check valve should be included too. I have seen where engines with bigger cams would make power brakes act up since the motor has less vacuum with alot of cam duration. Something to think about!

Boy, you guys sure made me think here! I do mostly linings and rotor-drum service at work, and general hydraulic repairs! We don't see many custom conversion jobs! Still, the brake system on a car is a pretty simple thing to service and improve. I've stuck with the stock drums on my Camaro but might swap in discs someday. It's easy on cars where disc brakes were an option that year because factory parts work!

I hope I could help some!

Sal

[parklane]

When I did the disc brake thing on my 54 Chev p/u, I had a AMC Pacer front suspension in it, and a 9" Ford rear end. I took a master cyl. and proportioning valve out of a 70 Ford p/u, with a M11 booster, put it under the floor, to keep the firewall clean. Worked like a champ!! Some say that you naad a residual valve if you have your master cyl. under the floor, but never put one on, and suffered no ill effects.

John

[WZ JUNK]

When I did the disc brake thing on my 54 Chev p/u, I had a AMC Pacer front suspension in it, and a 9" Ford rear end. I took a master cyl. and proportioning valve out of a 70 Ford p/u, with a M11 booster, put it under the floor, to keep the firewall clean. Worked like a champ!! Some say that you naad a residual valve if you have your master cyl. under the floor, but never put one on, and suffered no ill effects.

John

I have power brakes under the floor of my old truck.  I did not use residual valves and it has been driven many miles over the last few years.  Although the brakes work fine,  I have noticed that the pedal travel is now more than it use to be.  I think that as the pads and shoes are wearing they are traveling more and the pedal is moving more.  I have new residual valves on my desk somewhere and I intend to put them in the system soon.  It will be interesting to see how it changes the brake action.