Rear Disc Brake Conversion

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by Brizio, Sep 15, 2019.

  1. 8pack

    8pack Veteran Member Lifetime Gold Member

    Messages:
    2,619
    Likes Received:
    149
    Joined:
    Aug 29, 2007
    Location:
    Western, MA
    Do you know if these are any kind of performance improvement over the Transam rear disc set up and if the ebrake cable isn’t routed better to allow for a wider rear wheel.

    I am trying to fit 18x9.5 wheels with 5.75 BS and 275/40 tires and the ebrake cable on the TA set up looks like it is going to rub.

    Thanks!
     
  2. GDSmith

    GDSmith Veteran Member

    Messages:
    139
    Likes Received:
    26
    Joined:
    Aug 4, 2012
    Location:
    Glen Ellyn, IL
    Not sure about adding clearance, I would imagine based on the exit of the e-brake cable from the rear frame rails it wouldn’t matter what system you use the clearance would be the same. I’m running 18X8 with 4.5 backspace with about 2 of clearance between the tire and e-brake cable.
    What about the clearance between the leaf springs (if you have leafs).
    I would imagine there is someone out there that can better answer this question
     
  3. DesmoEd

    DesmoEd Veteran Member

    Messages:
    1,138
    Likes Received:
    7
    Joined:
    Sep 9, 2009
    Location:
    Frisco, TX
    My '73 has a WS6 TA disc brake rear end, courtesy of the previous owner.

    The brakes on the car have always been mediocre, even after checking the calipers, replacing rotors, and replacing brake lines and pads. It had a fairly new replacement booster/mc when I bought it but it still utilized the stock disc/drum single diaphragm booster. Engine is the built sbc in my signature and it pulls ~13.5 in vacuum at idle - marginal for a vacuum booster yes but I expected the brakes still to be better than they were.

    After doing some research, it looks like the TA used a dual diaphragm for good reason. From my info, a drum brake cylinder operates at a much lower psi vs a disc brake caliper (600 vs 1000-1200 psi) and thats the reason that GM went with a dual diaphragm for the 4 wheel disc TA cars. Also the proportioning/combo valve is specific to the disc/disc setup as well.

    I actually bought the TA specific booster/mc a while back and had planned to swap it in with an adjustable prop valve when I put in the TKO600 that's currently in the works. But after much contemplating, marginal vacuum, and not wanting to have to revisit brakes again on this car I decided to go with a hydroboost system and not look back.
     
    hubedobeedo likes this.
  4. GDSmith

    GDSmith Veteran Member

    Messages:
    139
    Likes Received:
    26
    Joined:
    Aug 4, 2012
    Location:
    Glen Ellyn, IL
    Did the same thing when upgrading to 4-wheel disc, Day and Night. Strongly recommend going this route.
     
    hubedobeedo likes this.
  5. badazz81z28

    badazz81z28 Veteran Member

    Messages:
    16,723
    Likes Received:
    465
    Joined:
    May 4, 2001
    Location:
    Las Vegas, NV
    I had 17x9s with 5” BS. It’s best to wire clamp the cable away from the wheel. It will rub, but there is enough slack to secure it away
     
    8pack likes this.
  6. Knuckle Dragger

    Knuckle Dragger Mayor of Simpleton Staff Member Lifetime Gold Member

    Messages:
    14,752
    Likes Received:
    1,298
    Joined:
    Nov 2, 2002
    Location:
    Waddell AZ

    The drums on the F-body are "self energizing" No fixed lower pin allows the primary shoe as it touches the spinning drum to drive the secondary shoe into the drum. That's why it takes less pressure and needs less boost assist.

    I agree when I went from vacuum boost to hydro on my WS6 brake conversion it was night and day difference.
     
  7. Skip Fix

    Skip Fix Veteran Member

    Messages:
    2,181
    Likes Received:
    23
    Joined:
    Mar 21, 2007
    Location:
    Katy,Texas
    My 81 TA dual diaphragm 4WD booster was good until my vacuum got 9" with a big cam.
     
  8. badazz81z28

    badazz81z28 Veteran Member

    Messages:
    16,723
    Likes Received:
    465
    Joined:
    May 4, 2001
    Location:
    Las Vegas, NV
    I recommend an adjustable proportional valve too.
     
    hubedobeedo likes this.
  9. giggity

    giggity Veteran Member

    Messages:
    920
    Likes Received:
    86
    Joined:
    Mar 18, 2013
    Location:
    Pearland, texas
    I was looking at a rear conversion kit, but im planning to change rims over to 18s, and curious if it will look goofy with 14inch rotors and 18 inch rims.
     
  10. GDSmith

    GDSmith Veteran Member

    Messages:
    139
    Likes Received:
    26
    Joined:
    Aug 4, 2012
    Location:
    Glen Ellyn, IL
    Guess it depends on your opinion. I have Hydra-boost and do not need larger brakes nor do I really worry too much what someone else considers "Looks Goofy". If you want to spend the bucks to appease someone else then by all means fill the wheel with rotor.
     

    Attached Files:

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.