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going from 11" drums to chevy disc brakes

Discussion in 'Early CJ5 and CJ6 Tech' started by cj6/442, May 16, 2015.

  1. May 16, 2015
    cj6/442

    cj6/442 Sponsor

    Fallbrook, Calif
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    with floor mounted pedals non power assist ,,,,,,,,do I need to change master cyl. I already have a dual master for my drum set up ... what inline pressure valve would you recommend ,and will I need to get an adjustable pressure thingy?
     
  2. May 16, 2015
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
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    I am not sure you will get better performance from the disks as apposed to the 11" drums. Maybe in wet weather or fording a stream. Anyway, you will need 2lb pressure residual valves. I am not at all convinced the are all manufactured to the highest standards. you may or may not need to adjust front to rear pressure bias to stop locking up the rears, i didn't. I had not so great luck with the stock style cj5 dual master. I went with a corvette disk/disk master. cheap. same bore size, but slightly longer stroke. I think the caliper mounting brackets move slightly and maybe my disks are not perfectly aligned on the rear allowing some issues that cause less than perfect brake pedal feel. They do work well enough though.
    http://www.earlycj5.net/forums/showthread.php?113500-brake-rant/page4&highlight=brake
     
  3. May 17, 2015
    tarry99

    tarry99 Member

    Northern California
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    Disc brake calipers take more volume.........the factory Disc / Drum Master for around 77-80 had a split reservoir that the Disc side was larger , But at that point AMC was using a large single 3" bore caliper. 2 lb valve as mentioned above, and sometimes you do need a proportioning valve while other times no..........If it was powered up probably yes. What size are the pistons in those calipers?
     
  4. May 17, 2015
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
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    Make sure to use organic pads also, semi-metallics take more pedal pressure to stop.
     
  5. May 17, 2015
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

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    I used semi metallic pads first off, then switched to organic. At first I did not notice any difference, but in the couple hundred miles either my leg has gotten stronger or my pads bedded in and work with less effort with a similar amount of miles that were on the semi metallic.

    In short, what he said.
     
  6. May 17, 2015
    Focker

    Focker That's a terrible idea...What time? Staff Member

    WA
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    It would be great to see a detailed write up with parts and pix of:
    D27 with disc brakes.
    D44 with 11" drums.
    Stock brake MC (if applicable) or what it took to safely run the brake system.
     
  7. May 17, 2015
    uncamonkey

    uncamonkey Member

    Greeley CO
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    I went from 9" to 11" on my 3B, no changes in the plumbing, OK, some of the brake lines need to be changed. They work better than the 10'' on the Commando with the brake booster.
    Water can be an issue. I suppose if I really felt like it, I could pull the parts off of the D30 in the yard and put them on the 3B.
    I don't feel like doing it...
     
  8. May 17, 2015
    homersdog

    homersdog Tulsa, Ok 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    I used R&p's 1/4 ton disk conversion kit which is based on Chevy S10 brakes. They work excellent. I am still not used to how quick they grab and I end up stopping short at stop signs.

    2 lb residual valve, original style 1971 V6 dual mc and proportional valve to dial back the rear drums pressure.

    11" probably work as well but I like this setup because they are more predictable in wet conditions and because of the coolness factor.
     
  9. May 18, 2015
    jzeber

    jzeber Well-Known Member 2022 Sponsor

    Morgan Hill, Ca
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    X2 on organic pads, made all the difference in the world.
    I used 87' 4x4 brackets and calipers. I originally had the M/C under floor. I was able to buy one made for disc front and drum rears.
    M/C PN: Dual Master Cylinder for 1971 - Raybestos MC36365
    Organic Pads for 1987 4x4 Chevy Truck PN: Raybestos RRD52
     
  10. May 18, 2015
    cj6/442

    cj6/442 Sponsor

    Fallbrook, Calif
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    I cant use the fat vette mc the frame is boxed in ......... and I should have said to ford disc brakes since my Hubs are the internal splined hubs no 6 bolt jeep hubs of me .
     
  11. May 18, 2015
    Focker

    Focker That's a terrible idea...What time? Staff Member

    WA
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  12. May 19, 2015
    jzeber

    jzeber Well-Known Member 2022 Sponsor

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    Thanks for reminding me. The PN for 1982 and 1987 is the same though.
     
  13. May 19, 2015
    Focker

    Focker That's a terrible idea...What time? Staff Member

    WA
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    Good to know...Thanks!
     
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