Another Disc Brake Conversion dilemma...

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by TheGreyT/A, Nov 26, 2019.

  1. TheGreyT/A

    TheGreyT/A New Member

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    I know I've seen this discussed on the forums. Have a 78 T/A. Previous owner put SSBC Force 10 calipers all the way around. It had an aftermarket dual diaphragm booster, master(that hit the hood). Proportioning valve has been replaced(not by me). Braided lines.
    I replaced the booster with a 1980 T/A 4wheel disc booster, and 80 model vette master. Problem is, pedal doesn't have much travel and brakes stop you...slowly. Booster is good. master was bench bled, and system has been bled 3 times. I do have a new proportioning valve that I KNOW is disc/disc that I could install.
     
  2. Vettenick

    Vettenick Vettenick

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    Not much into aftermarket stuff, but just a hunch, the rod on the booster that engages the master cylinder piston, it should barely touch that piston. If the rod is too far off, you definitely will have reduced master cylinder piston travel, and give you the symptom that you are experiencing.
     
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  3. TheGreyT/A

    TheGreyT/A New Member

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  4. Vettenick

    Vettenick Vettenick

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    Try to get a brake pressure gauge to measure what the pressure is at the different wheels just to see if the pressure is low front to back or vice versa, or low all around. Then you'll have a better idea of how to proceed. Another thing to consider, since there was a swap, is the brake pedal the correct one for the car?
     
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  5. TheGreyT/A

    TheGreyT/A New Member

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    I was thinking about checking pressure. That's something I should do anyway Though bleeding blew the hose off more than once lol. Pedal is stock. Booster and rod are 79 T/A
     
  6. Vettenick

    Vettenick Vettenick

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    One other item....Has the pedal rod been replaced from original due to the after market booster? I know sometimes you have to use a different pedal rod.
     
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  7. TheGreyT/A

    TheGreyT/A New Member

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    The pedal is stock. The previous booster had the adjustable pedal rod. The one on it now is OEM for 1979 Trans Am
     
  8. SRGN

    SRGN Veteran Member

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    Make sure the front and rear lines aren't switched going in/out of the proportioning valve. If you don't have enough pressure up front, the car will not stop well.
     
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  9. TheGreyT/A

    TheGreyT/A New Member

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    They are correct. Good point though. I've seen some that get switched in different set ups. I may change proportioning valve as well.
     
  10. SRGN

    SRGN Veteran Member

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    How much vacuum do you pull at idle?
     
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