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Brake proportioning Valve adjustment

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by smack, Sep 18, 2002.

  1. smack

    smack 1/2 ton status

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    Thought I read this before but couldn't find it.
    There is a way to adjust the brake proportioning valve to send more juice to the rears, right?
    If so, anyone know the correct proceedure?
    Thanks in advance,
    Smack
     
  2. 4x4Freak

    4x4Freak 1/2 ton status

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    I dont think it can be adjusted. That is why it has to be changed when converting to rear disc brakes. Of course I could be wrong.
     
  3. BigMac

    BigMac 1/2 ton status

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    No adjustments on the stock valve.... You may find you need a 3/4 ton master cylinder....
    If your brakes are locking out of sequence you can add an adjustable valve in line to the rear brakes.

    (standard disclaimer..my conversion isnt finished i just been doin my homework)
     
  4. beater74

    beater74 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    That is why it has to be changed when converting to rear disc brakes

    [/ QUOTE ] yup yer wrong /forums/images/icons/grin.gif /forums/images/icons/tongue.gif thats is not at all necessary. i've never seen or heard of any one changing the proportioning valve when doing a disco.
     
  5. smack

    smack 1/2 ton status

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    Hmmm, wonder then how I can fix the front tires from locking up on wet pavement.
    I keep readjusting the rears, and in fact have all new hardware including brand new star adjusters.
    Maybe I have a master cylinder that's gettin' tired???
     
  6. BobK

    BobK 1/2 ton status

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    I bought an adjustable prop. valve when I did my rear disc swap but ended up not using it.I've heard of people using them but it all depends on how much of the vehicles wt. transfers to the front under hard brakeing.My truck never really took a nose dive under hard brakeing even before the disc swap and that hasn't changed after the swap either.
    [​IMG]
     
  7. slider

    slider 1/2 ton status

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    Hey Big Mac what is the difference between a 3/4 ton and a 1/2 ton master cylinder? Will the 3/4 ton cylinder give more fluid to the rear? Thanks Slider
     
  8. smack

    smack 1/2 ton status

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    Is that valve intended to replace the stock one or supplement it??
    Might I assume you want to sell it then? How much??
    smack
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Actually I am hearing folks are bypassing the factory valve all together and it seems well ballanced that way. I think I'm going to bypass and put the adjustable in the rear line if I have any ballance problems. I keep so much junk in my truck it's about 50/50 weight.
     
  10. smack

    smack 1/2 ton status

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    weird, no balancer at all??? Maybe that would solve my problem 'cos it's intended to limit the rear power anyway, right?
    Any suggestoins on how to link them all together without the valve in there??
    TIA
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Right it also put is a small delay. Drums are self activating. They need no where near the pressure that the discs do. The disc's need more presure and volume. The stock master can't provide an even amount and what those have bypassed it are saying is it's about right.
    I'm trying to find the thread where one of the guys did that. He had a problem getting enough through the stock proportioning valve for the rears. So he bypassed it. THen the valve was mad and threw up the light and wias giving him problem with enough presure to the front so he completly bypassed it. Said it's the best they have ever been. The only thing I'm concerned about is if the proportioning valve has and deal where it keeps a few lb on the calipers. When you let off the master it will try to pull fluid back. If it pulled too much then you would end up with too much travel at the calipers before they contacted the disc. If that's the case a residual valve could be added to cure that problem. It will keep a couple pounds of pressure in the line.
    I'm getting ready to try this. I haven't decided what way to go. I'm leaning towards bypassing and if need be an adjustable in the rear line.
     
  12. BigMac

    BigMac 1/2 ton status

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    yes, that is my understanding... more fluid moved with the 3/4 ton unit.... Some guys that did the 4 wheel disk conversion were complaining that they really had to stand on their brakes to hold them stopped after the conversion... the fix being the bigger master cylinder and booster... My personal plan is to put the disks on and try them with all the rest of my components stock... cus Im a poo famly man livin in silicon valley

    well see how it works.
     
  13. smack

    smack 1/2 ton status

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    Grim, keep me posted on that, please, or I'll let you know what I do, Sounds like a residual valve would be smart but what kind of valve and where do you get it??
     
  14. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    ThatK30Guy Question for you!

    Here is another post about the same thing. Alec78 found this site and he said they have a Disc Disc truck proportioning valve he said.
    Now Something just came to me that might be of interst so Hopefully ThatK30Guy will see this and he might be able to help with this thought.
    K30's I believe run a load valve. What it does is it adds more brake presure to the rears as the load in the bed increases. There is a valve mounted under the bed that connects to the axle with a rod. So the more the rear sage the more it opens the valve. What I don't know is if or what they run as far as a proportioning valve. Maybe that would be more biased to a higher pressure on the rear cuircuit since that valve is there to adjust for the load. Maybe K30 guy will know a little about it. Still may be an issue with the delay built in for the drums.
     
  15. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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