Results 1 to 10 of 10

Thread: Brake master cylinders question

  1. #1
    Supporting Member Turbo Mopar Contributor
    Join Date
    Feb 2015
    Location
    toronto
    Posts
    1,765

    Brake master cylinders question

    I have a number of master cylinders either marked as "7/8" or "1" in the casting on the top just in front of the reservoir.

    The 7/8 measures up at 7/8 of an Inch so far so good but the "1" is "zackly" the same. Yes I was hoping for a larger MC for my big brake install...
    Any ideas what the "1" means???
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  2. #2
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
    Join Date
    Dec 2005
    Location
    Warsaw, NY
    Posts
    8,838

    Re: Brake master cylinders question

    odd. i would have though that was a 1" myself.

    ill have to look at my master cyl the next time it is off to see what the actual size is.

    mine is super firm but i like it cause its less sensitive so i can really mash them without locking them accidentally.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  3. #3
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
    Join Date
    Dec 2005
    Location
    Tuscola, IL
    Posts
    21,441

    Re: Brake master cylinders question

    I believe the 1 is for 21mm bore dia. The 4 is 24mm bore dia.

  4. #4
    turbo addict
    Join Date
    Dec 2005
    Location
    Spokane, Wa
    Posts
    9,046

    Re: Brake master cylinders question

    so 1 would be smaller than 7/8

  5. #5
    turbo addict
    Join Date
    Dec 2006
    Location
    MPLS, MN
    Posts
    3,589

    Re: Brake master cylinders question

    Yep 1=21mm, then 7/8", followed by 4=24mm, then the truck's (d-150)1-1/8" bore. The bigger you go the less pedal movement there will be, and the harder you will have to press on stop pedal. I took out all my 24mm MC on my L-bodies and installed the 7/8". IMO, a good compromise between modulation and adequate fluid quantity (flow and pedal travel). 7/8" for the win (lol)!
    Todd

  6. #6
    turbo addict
    Join Date
    Dec 2006
    Location
    MPLS, MN
    Posts
    3,589

    Re: Brake master cylinders question

    For all you guys with rear drum brakes and a seemingly super hard brake pedal, before you blame your too big of MC, I would check your rear wheel cylinders. They are probably frozen or in the process.
    They will bleed perfectly, but won't actuate much or at all. Doesn't seem to take much moisture in brake fluid to get those rear cylinders to not work correctly.
    Todd

  7. #7
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
    Join Date
    Dec 2005
    Location
    Tuscola, IL
    Posts
    21,441

    Re: Brake master cylinders question

    Quote Originally Posted by 4 l-bodies View Post
    Yep 1=21mm, then 7/8", followed by 4=24mm, then the truck's (d-150)1-1/8" bore. The bigger you go the less pedal movement there will be, and the harder you will have to press on stop pedal. I took out all my 24mm MC on my L-bodies and installed the 7/8". IMO, a good compromise between modulation and adequate fluid quantity (flow and pedal travel). 7/8" for the win (lol)!
    Todd
    What rear brakes for your 21mm MC? Actually, what are the front brakes? The 21mm MC is too little for my tastes with 11" brakes up front and the drums in my Lancer.

  8. #8
    Supporting Member Turbo Mopar Contributor
    Join Date
    Feb 2015
    Location
    toronto
    Posts
    1,765

    Re: Brake master cylinders question

    This is cool that there are three MC
    Last edited by chromguy; 02-01-2020 at 09:34 PM.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  9. #9
    turbo addict
    Join Date
    Dec 2005
    Location
    Spokane, Wa
    Posts
    9,046

    Re: Brake master cylinders question

    I've run the D150 MC and the 24 on 11" cars. The D150 does require quite a bit more force but is good for racing modulation. The 24 is STOP RIGHT NOW when you hit it good and hard. Lot's of fun on grandma's new yorker.

  10. #10
    Supporting Member Turbo Mopar Contributor
    Join Date
    Feb 2015
    Location
    toronto
    Posts
    1,765

    Re: Brake master cylinders question

    Quote Originally Posted by GLHNSLHT2 View Post
    I've run the D150 MC and the 24 on 11" cars. The D150 does require quite a bit more force but is good for racing modulation. The 24 is STOP RIGHT NOW when you hit it good and hard. Lot's of fun on grandma's new yorker.
    I use a 24 on my Sundance DD with 11 fronts and solid rears. the stopping is great with my Hawk pads (LTS winter and HTS summer)
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

Similar Threads

  1. Master cylinder, brake booster
    By Shadowv4l in forum Suspension, Brakes, Wheels, Traction
    Replies: 10
    Last Post: 03-08-2012, 10:09 PM
  2. Pedal Pressure for Various Brake Boosters and Master Cylinders
    By rbryant in forum Brake & Wheel Systems
    Replies: 0
    Last Post: 12-01-2011, 03:19 AM
  3. Need Help Identifying Master Cylinders
    By CDNTurboZ in forum "I need help!"
    Replies: 1
    Last Post: 06-26-2008, 12:27 AM
  4. 21 vs 24mm master cylinders...
    By flatlander757 in forum Suspension, Brakes, Wheels, Traction
    Replies: 14
    Last Post: 03-21-2007, 08:43 PM
  5. WTB: 2 - 24mm Master Brake Cylinders
    By devlish in forum Parts Wanted
    Replies: 1
    Last Post: 12-19-2006, 01:46 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •