Front disc swap and not much improvement?

Discussion in 'The whoa and the sway.' started by AlaskaBuick, May 21, 2005.

  1. AlaskaBuick

    AlaskaBuick Well-Known Member

    I just installed a front set of SSBC dual piston 11" brakes and they just are not working like they should? New master and booster, and still not much brake? The brakes should pin you to the steering wheel.

    The look impressive but much less in performance. Some thing has to be wrong. Holding 18 pounds of vac and with a solid pedal.

    Has anyone had this problem?

    Dennis
     
  2. GStage1

    GStage1 Always looking for parts!

    Did you change to the correct combo valve??????
     
  3. gotbuick

    gotbuick What, me worry?

    a.k.a. Proportioning valve. This is the unit that the brake lines run to off of the master cylinder.
     
  4. AlaskaBuick

    AlaskaBuick Well-Known Member

    Valve

    No, still have the stock drum brake unit.

    Do these go bad?

    Is their a difference in a drum proportioning valve and a disc?

    Where should I get the proper one from?

    I suspected that this may be the problem but wanted to get some feedback first.


    Dennis
     
  5. GStage1

    GStage1 Always looking for parts!

    Dennis,
    There is your problem. You must, I repeat, must, replace the drum distribution valve with a disc brake combo valve. Due to the large displacement of the caliper pistons, they require more fluid flow to operate properly. The drum dist valve send equal amounts of fluid flow to all wheels since they all have the same capacity wheel cylinders. Also, the disc brake combo valve lets the rear brakes work slightly before the fronts for proper brake operation. You will also need the disc brake mounting bracket for the frame. Or, you can mount it directly to the frame rail to gain additional exhaust-to-valve clearance.

    I should have some in stock. Please see the article on our site covering the change from drum brakes to disc brakes. Please email me off-list for pricing on the combo valve. GStage1@buickperformance.com
     
  6. sailbrd

    sailbrd Well-Known Member

    Also do not forget to remove the old residual valve that is in the line to the rear brakes.
     
  7. GStage1

    GStage1 Always looking for parts!

    He won't have the residual valve with drum brakes from the factory.

    Dennis, your combo valve was shipped this morning!
     
  8. AlaskaBuick

    AlaskaBuick Well-Known Member

    Thanks

    Thanks for the fast service George and all the advice.

    just paypal'd you.

    Dennis
     
  9. AlaskaBuick

    AlaskaBuick Well-Known Member

    Still no brakes

    Have replaced everything except the Brake lines on my car and still terrible brakes.

    Peddle is hard and pulling 18" of vac from a brake pump w/can.

    Is that enough VAC? Should I got to muanual?


    Their has to be something wrong?

    Dennis
     
  10. alan

    alan High-tech Dinosaur

    Do you have the lines hooked up correctly from the master cylinder? On my Wilwood setup (with rear disc also) the rear outlet goes to the front brakes, and the front outlet goes to the rear brakes. (if I remember correctly)
     
  11. GStage1

    GStage1 Always looking for parts!

    I assume you have the correct master cylinder for disc brakes. I am wondering if you have bad lines. The fronts are easy to replace. You can get them new from www.inlinetube.com
     
  12. 1979SHX

    1979SHX derevaun seraun

    Probably should replace all three rubber lines, if you haven't already done so (those may be what George is referring to). If they're old, they tend to swell and take some pressure away from the calipers. In some cases, they can separate inside and block fluid flow.

    I would think your 18" of vacuum should be enough. That doesn't affect your actual braking ability, anyway....just the way the pedal feels.

    Just another possibilty for you. Has to be something simple.
     
  13. sailbrd

    sailbrd Well-Known Member

    The best way to diagnose these problems is with a pressure testing kit. The one I got was about $100. Seemed expensive at the time but it does let you find the exact problem without a lot of part switching. Maybe a cheaper source out there someplace. Then you will know what the problem is instead of guessing. There is no reason for the sytem not to work if the line pressures are correct.
     
  14. AlaskaBuick

    AlaskaBuick Well-Known Member

    pressure

    Your right, I am going by a buddies shop tommarrow and have it texted. this will tell the story.

    All the rubber lines have been replace as well as the steel with the exception of the line running under the motor to the right wheel. I dont think that is the problem or I would pull to one side?

    They feel just like my drums did. Solid pedel with no brakes? very strange.

    Let me check the pressures and then we will start to nail it down.

    Thanks for all the advice guys.

    Dennis
     
  15. oldsmobuick

    oldsmobuick "A" Body nut

    It's possible the brake booster took a dump if the pressure checks out ok at the calipers and slaves :grin:
     

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