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Technical brake valves, proportioning & residual ?

Discussion in 'The Hokey Ass Message Board' started by SDS, May 14, 2021.

  1. SDS
    Joined: Apr 28, 2011
    Posts: 280

    SDS
    ALLIANCE MEMBER

    I am building a 1955 for f100 with discs in front, drums out back - GM proportioning valve. power master cylinder is under the floor.
    Do I need residual valves in the F&R brake lines?

    I'm also building a 32 roadster hi-boy with drums all the way around...40 juice in front, std 9" Ford 11" drums out back - manual master cylinder under floor.
    Do I need a proportioning valve and/or residual valves?

    Thanks in advance,
    Scott
     
  2. 325w
    Joined: Feb 18, 2008
    Posts: 5,653

    325w
    ALLIANCE MEMBER

    Yes on first question. Second probably not. Did the same on a model A and it stopped fine. Try for a master piston dia. Close to what the 39 was. This is my opinion.
     
  3. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,774

    V8 Bob
    ALLIANCE MEMBER

    The only time discs may need a (2 lb.) residual is when the calipers are higher than the master cylinder.
    All vintage drum brakes need a residual, while later drums will benefit with them, either internally in the master cylinder or inline with a 10 lb. valve.
    The rear duo-servo brakes on your '32 are much better than the non-servo Lockheeds on the front, which may require an adjustable proportioning valve to prevent early rear lockup, because the rear axle is way over-braked than the front!
     
    Last edited: May 15, 2021
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  4. 31Apickup
    Joined: Nov 8, 2005
    Posts: 2,774

    31Apickup
    ALLIANCE MEMBER

    It wouldn’t hurt to have an adjustable proportioning valve on the roadster, it’ll allow you to fine turn the system, worst case have it open all of the way.


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  5. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,526

    2OLD2FAST
    Member
    from illinois

    AFAIK ,residual valves are a waste of money .
     
  6. Why?, if the master doesn't have them (or "it" on a single master) then you do need them in line.....if the master is lower then the other hydraulics (calipers/wheel cylinders).
     
  7. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,774

    V8 Bob
    ALLIANCE MEMBER

    The auto industry would not have wasted money on them until the '70s if they were not needed. ;)
     
    Last edited: May 14, 2021
  8. Fabulous50's
    Joined: Nov 18, 2017
    Posts: 344

    Fabulous50's
    Member
    from Maine

    They give the benefit of keeping the shows close to the drum which gives a good pedal.

    Needed in anything where the wheel cylinders/calipers are higher than the master.

    10psi drum and 2 psi disc.

    Will work without them, but may not have breaks on the first pedal stroke...that would give me a stroke!
     
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  9. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,526

    2OLD2FAST
    Member
    from illinois

    Have either of you driven a vehicle without them ? If not your contention is pure supposition .
     
  10. 55blacktie
    Joined: Aug 21, 2020
    Posts: 464

    55blacktie

    Are you limited to using smaller brakes in front? If not, your front brakes should be equal to or greater in size than the rears. Of course, the T did not have front brakes, but I highly recommend them.
     
  11. kabinenroller
    Joined: Jan 26, 2012
    Posts: 716

    kabinenroller
    Member

    Will work without them, but may not have breaks on the first pedal stroke...that would give me a stroke![/QUOTE]

    I agree. I have Baer all the way around, when I built the car it had a dual master and a combination valve (recommended by Master Power Brakes) the car would not stop, even standing on the pedal made no difference. I removed the combination valve and replaced it with a Kelsey Hays adjustable proportioning valve, big difference, the car actually stopped great but the first pedal pump was soft. I bled the system with a vacuum bleeder, a pressure bleeder, and the old fashioned pedal pump method, it still had a soft first pump. I started doing research and read that a two pound residual valve in each system would help. (Front/rear)I installed the two valves and after bleeding the system using Speed Bleeders the pedal feel is consistent and firm. The car stops fast and hard. I made sure the valves were not allowing any pressure on the calipers, the wheels turn free and I can push the car by hand with out effort. Residual valves work.
     
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  12. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,526

    2OLD2FAST
    Member
    from illinois

    Why ?
     
  13. If the master is below the caliper/wheel cylinder it keeps the fluid from running back to the master, a check valve so to speak. With drums they were to keep 10lbs of pressure in the system to keep the cup seals in the wheel cylinder sealed upon brake release, now pretty much every wheel cylinder made has cup expanders which eliminates the need for residual valves for sealing purposes.


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  14. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,526

    2OLD2FAST
    Member
    from illinois

    Given that gravity would be the only impetus for fluid to move from wheel cylinders/ calipers to master cylinder , as no other force is being applied & that the seals in the cylinders/ calipers do not allow air to be ingested & the master cylinder is a closed unit , any fluid movement would be miniscule , at most , indeterminable , at least . the only benefit residual valves present is to the manufacturer & seller benefitting monetarily ,from them .
     
  15. kabinenroller
    Joined: Jan 26, 2012
    Posts: 716

    kabinenroller
    Member

    Well I guess you are correct and the automotive industry and thousands of car builders who have used them are wrong. Thanks for sharing your knowledge?
     
  16. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,526

    2OLD2FAST
    Member
    from illinois

    Your welcome !
     
  17. Actually when the brakes are released the return springs snap the shoes back which creates a low pressure in front of the cup seals and they can collapse allowing air in hence residual valves and now cup expanders.

    I post this not to argue, believe they are necessary or not, but to provide factual information for others.


    Sent from my iPhone using H.A.M.B.
     
  18. You have got to love a guy arguing with a someone who's career was brake systems with "I drove a car" as his proof.

    Sent from my SM-G950W using The H.A.M.B. mobile app
     
    57 Fargo likes this.
  19. iagsxr
    Joined: Aug 26, 2008
    Posts: 158

    iagsxr
    Member

    I have a race car that the master's mounted low but has a remote reservoir mounted that the top of it is just slightly higher than the calipers.

    Thing is the calipers hold more fluid than the reservoir. The reservoir does not create enough head pressure to keep the fluid from bleeding back.

    You could never get solid first stroke brakes in that system without a residual valve.

    Watertowers and brake systems, head pressure matters.
     
    Fabulous50's likes this.

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