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Technical General 50s single res M/C to dual (and booster) with drums all around

Discussion in 'The Hokey Ass Message Board' started by vintage44, Jun 18, 2017 at 6:35 PM.

  1. vintage44
    Joined: Dec 27, 2007
    Posts: 242

    vintage44
    Member
    from NY

    Looking to upgrade my '57 Buick from single res M/C without power to dual M/C with booster. I have drums all around. Discussing this with a friend he did the same process with a problem that cropped up. Apparently he installed the booster without checking what the PSI output would be. According to him the PSI of the front brakes was about 10 and the rear was about 2. This apparently caused the front brakes to eventually lock up. Antbody have any hints/advice/experiences for me?
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 35,314

    squirrel
    Member

    I think you are missing some information here....brake systems operate at hundreds of PSI.

    Are you talking about residual valve pressure ratings?
     
  3. vintage44
    Joined: Dec 27, 2007
    Posts: 242

    vintage44
    Member
    from NY

    Squirrel, wish I could tell you. I'm way out of my element when it comes to this. I was looking to use an '85 Astrovan M/C and booster (which I saw being used in a similar fashion on a similar vehicle) because of its 8" - 9" booster diameter since that's about all the room my Buick has.
     
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 35,314

    squirrel
    Member

    What is the issue with your brakes, that makes you want to change the master cylinder?
     
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  5. vintage44
    Joined: Dec 27, 2007
    Posts: 242

    vintage44
    Member
    from NY

    Just looking to add some backup protection so if a wheel cylinder blows I still have stopping power on the opposite end. Plus a bit more power adding a booster.
     
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 35,314

    squirrel
    Member

    huh, I haven't known wheel cylinders to blow. I do keep up on maintenance, though.

    Having some extra pedal help would be nice.

    If you do the dual cylinder conversion, be sure you understand how pedal leverage works, also pedal travel vs. master cylinder travel. If you set it up so the pedal bottoms before the master cylinder does, then you won't get the benefit of a dual system. You can test to see if it is working, by opening a bleeder on one wheel cylinder, and see if the brakes still work on the other end. If the pedal goes to the floor, you might as well have left it single.
     
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  7. vintage44
    Joined: Dec 27, 2007
    Posts: 242

    vintage44
    Member
    from NY

    Thanks, squirrel. Having grown up in a junkyard and driven a number of vehicles of questionable "maintenance", I have experienced both blown brake lines and wheel cylinders. I'm not going to rely on my limited skills in this area to do a proper conversion. Like most of us I have buddies whose skills cover things mine do not.
     
  8. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,003

    V8 Bob
    ALLIANCE MEMBER

    If I remember correctly, your manual '57 has a rather complicated compound pedal linkage and is slightly different from a power assisted arrangement. Pedal ratio is very important, as manual ratios are usually about twice the power ratios, and power front drum brakes can be overly aggressive with the wrong ratio, although you always want the fronts to slide before the rears.
    Converting to a dual master is a smart move, but must be done correctly as squirrel pointed out, or the safety advantage may not be fully utilized.
     
    squirrel likes this.
  9. belair
    Joined: Jul 10, 2006
    Posts: 6,625

    belair
    Member
    1. H.A.M.B. Chapel

    I've always gone to front disc, non-powered brakes. Properly set-up and in good condition, your brakes should be good for one good, long panic stop. Then you have time to change your underwear while the brakes cool off. I like the discs for better wet weather, low maintenance, straight stops every time. The 10 - 12 pounds are for the the residual pressure you need for the disc brakes, I think. There are valves you install in-line for that. Call Scarebirds. They do disc brake kits for old cars. I love 57 Buicks.
     
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 35,314

    squirrel
    Member

    drum brakes want around 10 psi, discs around 2 psi (so they release)
     

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