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Dual Master For Disc Brakes But Still Have Drums.

Discussion in 'Early CJ5 and CJ6 Tech' started by Primer Coat, Jul 31, 2022.

  1. Jul 31, 2022
    Primer Coat

    Primer Coat New Member

    Ohio
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    Jul 17, 2017
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    32
    I think I know the answer but there are much wiser and experienced folks here:
    Like many time and money are factors in my projects.
    I plan on upgrading the brakes on my 62 CJ5 to discs at some point, but want to put in a dual master cylinder now so I want to add the disc brake master cylinder now and the discs at a later date. Assuming the disc master cylinder puts out more pressure than the drum master is that going to be a problem.

    Thanks in advance.
     
  2. Jul 31, 2022
    skipilot

    skipilot Member

    Joined:
    Dec 16, 2007
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    75
    The stock dual master for the 67-71 has residual pressure check valves in the outlets that can be removed when going to disks. For drums you need about 10lbs of residual pressure and only 2 for disks. You can just use the stock dual master as is for your drums then when you go disks, remove the RPCV from the appropriate circuit and install a 2lb valve inline. The master has 2 large nuts on the outlets, the RPCV is under the nuts. Some people use different masters, how you would handle those would depend on their original application but if you used one that was designed for disks, you could use an inline 10lb RPCV. Willwood makes them and they are available at the usual suspects, Summit, Jegs, Speedway, ext. You could probably order it off Amazon. Happy wrenching.

    Tim
     
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  3. Jul 31, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    As I understand it, the 2psi residual pressure valve is only used in systems where the master cylinder is at or below the level of the brake cylinders, ie through-the- floor pedals. Speedway sells the 2psi residual valves, likely Summit or Jegs too. I presume you'd need one for each circuit, front and rear. If you go to hanging pedals, you don't need it.

    I'd also use a disk-disk combination valve, which would prevent rear wheel lockup in hard braking, along with providing a brake failure warning switch.

    There is plenty of info online about this if you search.
     
  4. Jul 31, 2022
    Primer Coat

    Primer Coat New Member

    Ohio
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    Jul 17, 2017
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    32
    Maybe I missing something but its a 62 with a single reservoir master cylinder, what does 67-71 have do to with my question?
     
  5. Jul 31, 2022
    Oldpappy

    Oldpappy A.C. Fults - Curmudgeon at large 2022 Sponsor

    East Tennessee
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    Probably because you said "want to put in a dual master cylinder now" and "Skipilot" was mentioning something useful about the dual master cylinder used on later Jeeps. Don't get your panties in a wad, he was trying to help.
     
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  6. Jul 31, 2022
    Jw60

    Jw60 That guy 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sedalia MO.
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    Just use the later dual master cylinder. The residual valves are easy to remove or do that now and use the 10lb inline valves then swap to 2lb valves when you go disk.

    Either way you need the 2lb valves later.
     
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  7. Aug 1, 2022
    Tinkerfool

    Tinkerfool New Member

    montana
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    Jul 7, 2022
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    Herm also has kits (same kit also sold at Kaiser) and are quick to respond to questions. As others have stated you can run the "disc" dual master now and add the appropriate valving later. It can get confusing because kaiser and herm's sites say they are different but when I contacted them, they said the something everyone else is saying.
     
  8. Aug 1, 2022
    Primer Coat

    Primer Coat New Member

    Ohio
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    Jul 17, 2017
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    Thank you. Those are the kits I am looking into.
     
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  9. Aug 1, 2022
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    Sep 22, 2002
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    I have a 71 with a factory dual master cylinder and the thru floor pedals. I run a 77 Dana 30 up front with factory manual disks brakes, I have the Wilwood residual pressure valves. It’s all factory Jeep parts and works well. Disk up front 10” drums in the back, no stopping problems at all.
     
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  10. Aug 1, 2022
    Lockman

    Lockman OK.....Now I Get It . 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Silver Hill,...
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    Like timgr said , your gonna do well to plumb one of these in too.........when you do the disc changeover.
    proportion-valve-pv2-1.jpg New Proportioning Valve 3-15-2019.jpg
     
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  11. Aug 5, 2022
    CJeep5

    CJeep5 New Member

    California
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    Mar 23, 2018
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    do you have a picture of the MC installed? I have something going hokey on my install and need some picture evidence. (need to see what i am messing up)
     
  12. Aug 6, 2022
    Lockman

    Lockman OK.....Now I Get It . 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Silver Hill,...
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    Here You go :
    Part # Master Cyl.JPG
    Top Pic of HydroBoost MC.JPG
     
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