Question on brakes

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by ULTM8Z, Dec 24, 2017.

  1. ULTM8Z

    ULTM8Z Veteran Member

    8,324
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    May 19, 2000
    Los Angeles
    The fronts are braided steel. The rear is rubber. I do know that it was replaced with a new one when I did the conversion though.

    But if I was losing hydraulic pressure from that, wouldn't I notice kind of a soft pedal with the engine off too?
     
  2. Skip Fix

    Skip Fix Veteran Member

    2,005
    4
    Mar 21, 2007
    Katy,Texas
    It's bee so long I do not remember the stroke, just I had hardly any brake feel until I switched. I think that was some of the "feel" issue was travel. Just doing the lever arm math it would have to change it some, part of why switching to the upper hole for manual you get more travel also I would think.
     
  3. ULTM8Z

    ULTM8Z Veteran Member

    8,324
    45
    May 19, 2000
    Los Angeles
    My current pedal ratio is about 3.5:1 using the bottom hole.
     
  4. ULTM8Z

    ULTM8Z Veteran Member

    8,324
    45
    May 19, 2000
    Los Angeles
    Doing some searching online.... One guy made a statement on another message board that seems to sum up what I"m feeling...

    That's pretty much what it feels like. It seems I'm getting a lot of vacuum assist, but it just doesn't seem to translate into force at the calipers.
     
  5. ULTM8Z

    ULTM8Z Veteran Member

    8,324
    45
    May 19, 2000
    Los Angeles
    Before calling Baer, I went around the car yesterday one more time with the vacuum pump and bleeder kit. I think I've pretty flushed out all the old fluid at this point for the amount of fluid I pulled through the system.

    But this time I did feel a significant improvement in brake feel. Not sure if the old fluid was contributing to the problem (I don't remember the last time I flushed out the fluid... if I've ever done it at all).

    It's still not quite where I would consider it optimal. I'll probably call Baer and see what can be done (if anything) to improve it. Meantime I'll probably also replace the rear rubber brake line (my fronts are the braided lines from the kit).
     
  6. 8pack

    8pack Veteran Member Lifetime Gold Member

    1,926
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    Aug 29, 2007
    Pittsburgh, PA
    This is the first time I have heard of the 4 wheel disc pedal and booster. I did the rear TA Brake swap years ago and used the old stuff from my Camaro except I changed out the master cylinder for DD and the proportioning valve.

    What is the correct booster and Pedal set-up?

    Not looking to hijack the thread, the answer seems relevant to the problem. I can do a separate post but it seems since the topic was raised here it is the best place to get it answered.

    Thanks!
     
  7. badazz81z28

    badazz81z28 Veteran Member

    14,177
    110
    May 4, 2001
    Las Vegas, NV
    Is there any validity to the specific pedal for 4 wheel disc???? I don't think there is ...I have done the 4 wheel disc conversion on 3 different cars. 2 using the stock Camaro pedal and my current car with OER Camaro pedal with BAER brakes with 1981 Trans Am disc/disc booster and MC. Not a single issue.....Many problems I see on here are simply related to air in the system or a faulty booster/MC. Speed Bleeders are awesome to get all the air out. The old school push pedal/crack bleeder doesn't always work especially if air escapes past the threads.
     
  8. NOT A TA

    NOT A TA Veteran Member

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    36
    Feb 12, 2009
    Delray Beach Florida
    The 4 wheel disc cars came with the disc/disc master cylinder, smaller diameter dual diaphragm booster, disc/disc combination valve, and a 4 wheel disc pedal. Various combinations of components will function with the front factory calipers and the late 2nd gen bird rear discs such as, disc/disc master cylinder with different than stock bore size, standard disc/drum booster, adjustable bias valve for rear brakes, and pedals with different ratio than a disc/disc pedal. However most combinations don't work quite as well together as the factory set up designed by GM engineers. So the pedal may feel too hard or soft, travel may be too long or short, and braking capability may not be as good as stock. I haven't seen a mismatch set up that seems to be better than stock when using the stock front 2nd gen calipers and stock bird rear calipers. Switching to aftermarket calipers or other options like the 1LE set ups are a whole different case.

    Here's a couple pics of the factory Pontiac 4 wheel disc booster/master/combination valve on an 80 Formula. Sorry forgot to take a pic of the pedal when I worked on the car.

    [​IMG]

    [​IMG]
     
  9. NOT A TA

    NOT A TA Veteran Member

    149
    36
    Feb 12, 2009
    Delray Beach Florida
    The hole for the 4 wheel disc clevis is close to where the hole for the disc/drum clevis is so unless you tried both on the same car you probably wouldn't notice the difference in pedal stroke and the brakes would feel similar driving on the street. BUT, you might be able to have them work better to reduce stopping distances.

    You might be leaving braking capability on the table with the Baer calipers depending on other variables like tires. I don't have the math skills but there are formulas that can be used with info about boosters, piston sizes, car weight, tire sizes and models, master piston sizes, pedal ratios, pad friction coefficients, etc. so you can optimize the system for a particular use like road track, auto-X etc. I have Ron Sutton do the calcs. As an example on my personal car I have 14" Baers with 6 pistons all around and am installing dual manual master cylinders with a driver adjustable bias bar and a custom ratio pedal. I lost power assist once on the front straight at PBIR and was both feet on the brake pedal with all my might to slow the car enough to only end up 2 wheels off. Luckily I didn't crash the car. It was very scary and I decided right then, no more power brakes on track.
     
  10. ol' grouch

    ol' grouch Veteran Member

    1,181
    197
    Jul 4, 2013
    Evansville, In.

    When I raced, we would convert the car to 4 wheel drums. We's remove the self adjuster and loosen them until they barely touched. Good for a couple 10th's.
     

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