Residual Pressure Valves

[Johnny]

Okay, guys, I'm getting ready to run brake lines. Yay or Nay to the risidual pressure valves. I'm cheap and I don't want to spend money on things I don't really need. To my way of thinking, it's a closed system and if it is bled correctly why would you need those valves?

Also, which line to you install the proportioning valve in? Front brakes or rear?

Thanks guys. I really appreciate your help.

 

[GT63]

Okay, guys, I'm getting ready to run brake lines. Yay or Nay to the risidual pressure valves. I'm cheap and I don't want to spend money on things I don't really need. To my way of thinking, it's a closed system and if it is bled correctly why would you need those valves?

Also, which line to you install the proportioning valve in? Front brakes or rear?

Thanks guys. I really appreciate your help.

NAY, Not needed. think about it. Where is the fluid gonna go in a closed system? Even Wilwood admitted to on of the members that they're not needed.

 

[fuzzy]

My understanding of residual check valves is that back in the day when all cars had drum brakes, check valves were built into the master cylinder. Without the check valve drum brake shoes have return springs that will pull the pistons in the wheel cylinder togetger till they stop, pushing most of the fluid back into the master cylinder. This will make the brake pedal travel further to refill the wheel cylinder until the shoes hit the drum. But disc brakes don't have return springs so it would seem no check valve is needed. If you have a disc/drum system a check valve [10 lbs is recommended] would be a good idea on the drum side of the system.
A proportioning valve is used to reduce pressure to the rear brakes so that when you apply brakes and the weight is transfered off the rear tires they won't lock up before the front brakes. If you're using large rear tires that will grip well you may not need the proportioning valve. If this is your cars design I would try no proportioning valve for the rear until you can road test to see how the brakes are working. Just a note about adjustable proportioning valves that some people are not aware that adjustable valves are preset at static 40% pressure reduction so you can't adjust to 0 pressure reduction.

 

[EX JUNK]

I have two street rods and I have residual pressure valves in both cars. I have had NO bad experiences in either car and I'm also using DOT 5 ( silicone) in both. They both were bled very easily and have a firm pedal.

Jim

 

[ruggs]

I don't really want to tell anyone when a residual valve is nessesary but, the location of your master cylinder is the important part. Ya gotta do your homework.......Ron (ruggs)

 

[HAceT]

Nay... I had the valves and had never had a comfortable pedal in my car. I removed them and now have a great pedal. I guess to each his own. I agree a closed system where will the fluid go. :shrug2:

 

[Duke]

One of the reasons they were used, is when the master cylinder is mounted below the level of the calipers or wheel cylinders. The fluid would run back to the master cyl. and it would overflow.

 

[Differen T]

I did quite a bit of research before buying the parts for my brake system- S10 front discs and drums on the rear with the master cylinder located below the floor, hence lower than the calipers and wheel cylinders. The master cylinder is from a mid 60's Corvette and has bore and capacity similar to the S10. The MC supplier does not sell residual valves but told me I needed them, 2lb front and 10 lb rear located as close to the MC as possible. The reasons given were prevention of drain back into the MC and better pedal response. I was also told to and did install a brake proportioning valve in the rear brake line. Unfortunately I am not ready to install fluid so I can't give you a final verdict.

Al

 

[Chief-T]

I did quite a bit of research before buying the parts for my brake system- S10 front discs and drums on the rear with the master cylinder located below the floor, hence lower than the calipers and wheel cylinders. The master cylinder is from a mid 60's Corvette and has bore and capacity similar to the S10. The MC supplier does not sell residual valves but told me I needed them, 2lb front and 10 lb rear located as close to the MC as possible. The reasons given were prevention of drain back into the MC and better pedal response. I was also told to and did install a brake proportioning valve in the rear brake line. Unfortunately I am not ready to install fluid so I can't give you a final verdict.

Al

This is the set-up I have and I have great brakes.

 

[Lee_in_KC]

All four of my brake calipers are above my master cylinder and I have no RPVs. I have had no "drain-back" to my m/c (Mustang) in the four years the T has been on the road. Personally, I don't see how there can be drain-back in a closed system like these brake systems. In order for brake fluid to flow out of the calipers there would have to be some sort of vent to break the vacuum that would be created as the fluid tried to drain out of the caliper. I could see if you had a leak in the caliper where you could get drain-back, but not in well-sealed installation. Just my 1.6 cents (inflation).

 

[Johnny]

Okay, I don't believe I'm going to spend the money on the valves.

Thanks guys

 

[tnoftsger]

All four of my brake calipers are above my master cylinder and I have no RPVs. I have had no "drain-back" to my m/c (Mustang) in the four years the T has been on the road. Personally, I don't see how there can be drain-back in a closed system like these brake systems. In order for brake fluid to flow out of the calipers there would have to be some sort of vent to break the vacuum that would be created as the fluid tried to drain out of the caliper. I could see if you had a leak in the caliper where you could get drain-back, but not in well-sealed installation. Just my 1.6 cents (inflation).

I don't think the "Drain back" is an actual draining fluid from the calipers or wheel cylinders. It is gravity pulling down on the fluid and causing the caliper piston/wheel cylinder piston to retract some distance further than it would normally if the MC were above the brakes.

1 vertical foot of drop causes about -0.5 psi of vacuum to be pulled on the caliper/wheel piston. Not much, and why some people don't need the valves.

 

[Lee_in_KC]

I don't think the "Drain back" is an actual draining fluid from the calipers or wheel cylinders. It is gravity pulling down on the fluid and causing the caliper piston/wheel cylinder piston to retract some distance further than it would normally if the MC were above the brakes.

OK, now that makes sense to me. Would that explain why I get a harder pedal if I double-pump? (no wise cracks!) :nono:

 

[GT63]

OK, now that makes sense to me. Would that explain why I get a harder pedal if I double-pump? (no wise cracks!) :nono:

Dang Lee, I thought you were blown ROFL

 

[Gerry]

OK, now that makes sense to me. Would that explain why I get a harder pedal if I double-pump? (no wise cracks!) :nono:

Lee
Boy, you make life hard at times
G

 

[Differen T]

There is one important piece of information that I was given and failed to post. Some master cylinders have check valves built in. I'm sorry but I do not have any examples to give out. I was told that the MC I used did not have check valves.
If double pumping gives you a harder pedal maybe you need to have your system checked by a professional. :wow:

 

[EX JUNK]

Okay, I don't believe I'm going to spend the money on the valves.

Thanks guys

You are not talking a lot of money here. If you go with the Wilwood residual valves and proportioning valve you'll spend about $78. If you go with Speedway valves you'll save about $15. To my way of thinking, you'd be wise to put them in rather than finding out later that you need them because you can't get a full pedal with the first push or that it does not stop correctly. In the big picture you are really not saving much and brakes are MUCH more important than go power. IMHO

Jim

 

[benT]

I bought a set of them when I was putting together my brake setup. At the advice of others on this and another board, I skipped installing them. I never really understood the real world reason for them. I decided that I could add them later if needed. Now my MC set up is a bit different then other here I imagine: A non-power Ranger disc/drum MC mounted under the dash with a Wilwood prop valve. Brakes are standard S10 drum in the back and GM metrics in the front. I have awesome pedal and have had no reason to add the residual valves. I ended up selling them for half of what I bought them for. The guy buying them insisted that he needed them on his street rod because he read where Wilwood recommended them (of course they recommend using their product!). I do recommend the prop valve. I was able to dial the back brake in properly. Like Jim says, you can buy the Speedway or Jegs' branded valves cheaper than the Wilwoods. Good luck!

 

[EX JUNK]

I bought a set of them when I was putting together my brake setup. At the advice of others on this and another board, I skipped installing them. I never really understood the real world reason for them. I decided that I could add them later if needed. Now my MC set up is a bit different then other here I imagine: A non-power Ranger disc/drum MC mounted under the dash with a Wilwood prop valve. Brakes are standard S10 drum in the back and GM metrics in the front. I have awesome pedal and have had no reason to add the residual valves. I ended up selling them for half of what I bought them for. The guy buying them insisted that he needed them on his street rod because he read where Wilwood recommended them (of course they recommend using their product!). I do recommend the prop valve. I was able to dial the back brake in properly. Like Jim says, you can buy the Speedway or Jegs' branded valves cheaper than the Wilwoods. Good luck!

As you said Ben, your master is above your calipers and rear cylinders so you had no need for the residuals as the fluid would not be affected by gravity and run toward the master cylinder. Adding a proportioning valve is a very wise idea in these light cars.

Jim

 

[Francis Blake]

I just found out firsthand that I can't use residual pressure valves in mine. I installed them bled my brakes,and my front wheels will not turn so that answers that question, at least for my car. Two steps forward and one back but I"m gettin there.