manual disc brake versus power disc brake master cylinders

Discussion in 'Technical' started by coutangman, Jan 30, 2015.

  1. coutangman

    coutangman Member

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    Are the master cylinders the same for manual disc brakes and power disc brakes? Most of the parts stores do not separate them, simply listing them as power disc brakes. Rock Auto lists them both as being the same. I am converting my '72 Comet GT to manual disc brakes and want to get the correct master cylinder. What did you use with your conversion? What year master cylinder works best?


    Jim
     
  2. yellow75

    yellow75 MCCI Oregon State Rep Supporting Member

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    Generally a power disc brake master cylinder will have a slightly larger bore 1 1/8 inch and bigger, non power master cylinders are smaller than 1 inch bore. If you are just going to be manual disc brakes just get the one for a 74 Mav with disc brakes. Power disc brakes for a Maverick were not an option until 75 I believe.

    I am sure everyone will have their own take on what to use but this is what I would do if I was to change master cylinders, but I would probably just use the master cylinder that was in the car
     
  3. coutangman

    coutangman Member

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    Mike,
    Rock Auto and Advance show the same part number for 1974, 1975, and 1976 for disc or power disc. What effect would the larger bore have on stopping? The one in the car is for drums, which I am told would make stopping more difficult. By the way, how are things going? I finally got off my butt and hope to finish this project, finally. Bought it in August of 1997. Time flies.
     
  4. mavgrab302

    mavgrab302 MCCI Florida State Rep

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    I'm using a 76 disc master with a npd adjustable push rod... When I bought mine at carquest they had a listing for manual disc brakes...
     
  5. yellow75

    yellow75 MCCI Oregon State Rep Supporting Member

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    Hey Jim I have been doing great its not like you dont have other cars to drive and places to go so whats a few years to get going on a project. LOL I went into Rock Auto and looked at what they had to offer and it is confusing but if it were me I would buy the Centric 13061033 as it is listed for manual disc brakes and the price also indicates that it is a new unit instead of a rebuilt one, it is one of the 2 that has the heart icon on it.

    The difference in bore size as I understand it is with the larger bore there is less pressure for the amount of pedal travel and a power disc brake master cylinder would have a deeper cup where the brake push rod goes between booster and master so if you used that one you would have to have a longer brake push rod.

    Now that I made things as clear as mud for you have fun
     
  6. dyent

    dyent Member

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    Here is a video that may help answer some of your questions.......



    Jim:
    did you manage to install you rear tail light lenses yet?
    David
     
  7. coutangman

    coutangman Member

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    Information overload! I felt like the guy in the chair, lol !! KISS !! Just tell me what master cylinder to use !! I do appreciate your effort, David, and no, the lenses are still in the boxes. I have had them out and they will look super when I do get to them. I'm working on it, believe me. I have been distracted by other projects and an older woman. Now, I am just distracted by older cars. Much cheaper and less stressful.
     
  8. dyent

    dyent Member

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    Unfortunately with our cars being 40 years old, parts supply houses tend group everything as one size fits all, the old supply and demand........After reading many same posts that other members are having, unless you can find an exact Ford replacement part, it is going to be a bit of a trial and error to see what will work with your particular set up. I think most OEM master cylinders where of 7/8" or 1" bores, but you may also have to play around with push rod lengths too get the correct pedal height YOU like........
    If your current disc/drum MC is in good working condition, just trying using it first.......

    www.ssbrakes.com has a very informative site when it comes to bleeding system, testing out your master cylinder and all the "myths" about spongy pedal etc.......I know it maybe alot of "information overload" but again, these are your brakes!
    Or in doubt, take it to a good brake shop at least whole system will be checked out and if something goes wrong, fault is on them and not you.........
     
    Last edited: Jan 31, 2015
  9. Krazy Comet

    Krazy Comet Tom

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    The larger the piston in M/C the harder the pedal will be... For easier braking use no more than 7/8-15/16, if I could find one I'd go 3/4"...

    BTW mine has a '74 disc M/C, will be looking at either power brakes or maybe a small bore M/C if I can find one...
     
  10. Xnke

    Xnke Member

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    The smaller the brake master cylinder diameter, the longer the pedal throw, but easier the push. The larger the brake master diameter, the harder the push, but the more fluid displaced and thus the shorter the pedal throw.

    For manual brakes, stick with a smaller diameter master. Keep in mind that you STILL have to move enough fluid, no matter how big or small the master cylinder diameter is, to move the caliper pistons. Bigger brakes need more fluid displaced, so they need a bigger master cylinder diameter OR a longer pedal stroke. It's a balancing act.
     

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