Let's talk brake master cylinders - Specifically for disc disc applications

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    Author Topic: Let's talk brake master cylinders - Specifically for disc disc applications  (Read 3119 times)

    Offline 70chall440

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    Let's talk brake master cylinders - Specifically for disc disc applications
    « on: February 05, 2019 - 12:03:05 AM »
    So, here is what I am currently running in my 73 Cuda. I am looking for advice/information for anyone else running a 4 wheel disc brake set up.

    MC: Mopar manual brake MC from perhaps an A body or perhaps B body (can't remember now)
    Front calipers: 02 Viper
    Rear calipers: 88 Cobra
    Proportioning/metering valve: Disc/Disc
    Other: I have an Wlwood adjustable proportioning valve as well for rear bias adjustment

    This combination was not selected randomly, a friend of mine ran the exact set up in his Lemons car (66 Barracuda w/ a 225). I am not running any booster at all.

    My issue is this, I just the car running and while the brakes will stop the car, they do not feel "solid" and will not lock. Granted, the pads are not broken in yet but it has me thinking of going to either a booster and/or a new MC. In reality I need to drive the car some more and see how it works out but never one to just leave crap alone, I thought I would throw it on here and see what you guys think or have done.
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    Current Mopar
    70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
    05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
    Past Mopars
    9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)


    Offline rusty dodge

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    • 74 challenger 440-727-3:55
    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #1 on: February 07, 2019 - 01:45:39 PM »
    Hydroboost. That should be the first mod done to a disc brakes setup before spending more on multi piston calipers. You can get cheap pressure gauge that goes into bleeder. When I checked mine i only got about 900 psi. Need more like 1500psi. I tried with the vacuum booster and also 15/16 bore manual setup without booster and only 100psi difference. Hydroboost is next on my list to get. If you happen to have high vacuum like over 16, then maybe that would work. I think the extra linkage on the brake pedal for the vacuum booster hookup actually takes away the pedal leverage when compared to manual brake hookup. Thats why I didn't see much difference? But thats just a guess.
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    Offline 70chall440

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #2 on: February 07, 2019 - 01:51:40 PM »
    I will take a look at it. I am running something like 12-14 in of vacuum currently.
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    Current Mopar
    70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
    05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
    Past Mopars
    9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

    Offline GoodysGotaCuda

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #3 on: February 08, 2019 - 07:20:21 AM »
    I have manual discs and have no problem locking them up. My current tires are quite dated, but the car is definitely tire-limited [not brake] when it comes to slowing down. New tires will be here next week, but I don't expect any issues.

    Break-in the pads and most brakes need some level of heat [if not, a lot depending on the compound] to really come to life.


    I've avoided hydroboost due to the lack of pedal feel, which becomes problematic for performance driving/threshold braking. It is just fine, however, for solely running down the road and getting around.

    I may get to a vacuum assist at some point, but for now, my Wilwood pad knockback is more of a problem than anything.
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    Build Page: Goody's 'Cuda Build Page
    1976 Dodge Warlock
    1972 Barracuda - 5.7 Hemi + T56 Magnum

    Wheel & Tire Specs:Link

    Offline 70chall440

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #4 on: February 08, 2019 - 12:20:14 PM »
    Quote from: GoodysGotaCuda on February 08, 2019 - 07:20:21 AM
    I have manual discs and have no problem locking them up. My current tires are quite dated, but the car is definitely tire-limited [not brake] when it comes to slowing down. New tires will be here next week, but I don't expect any issues.

    Break-in the pads and most brakes need some level of heat [if not, a lot depending on the compound] to really come to life.


    I've avoided hydroboost due to the lack of pedal feel, which becomes problematic for performance driving/threshold braking. It is just fine, however, for solely running down the road and getting around.

    I may get to a vacuum assist at some point, but for now, my Wilwood pad knockback is more of a problem than anything.

    Goody - what MC are you running, more specifically what bore size? I discovered that my MC is 1 1/32 bore, I just ordered a new Dr. Diff aluminum 15/16 MC. The MC I have is a auto parts store rebuild and has been suspect from the beginning.
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    Current Mopar
    70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
    05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
    Past Mopars
    9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

    Offline GoodysGotaCuda

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #5 on: February 08, 2019 - 12:24:49 PM »
    Quote from: 70chall440 on February 08, 2019 - 12:20:14 PM
    Goody - what MC are you running, more specifically what bore size? I discovered that my MC is 1 1/32 bore, I just ordered a new Dr. Diff aluminum 15/16 MC. The MC I have is a auto parts store rebuild and has been suspect from the beginning.

    I have used both 7/8” and 15/16”. I prefer 15/16”. Wilwood

    6piston front and 4piston rear calipers.


    Sent from my iPhone using Tapatalk
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    Build Page: Goody's 'Cuda Build Page
    1976 Dodge Warlock
    1972 Barracuda - 5.7 Hemi + T56 Magnum

    Wheel & Tire Specs:Link

    Offline 70chall440

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #6 on: February 08, 2019 - 06:00:58 PM »
    Quote from: GoodysGotaCuda on February 08, 2019 - 12:24:49 PM
    I have used both 7/8” and 15/16”. I prefer 15/16”. Wilwood

    6piston front and 4piston rear calipers.


    Sent from my iPhone using Tapatalk

    Thanks for the information I ordered a 15/16 MC from Dr. Diff so we will see how that works out.
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    Current Mopar
    70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
    05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
    Past Mopars
    9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

    Offline GoodysGotaCuda

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #7 on: February 08, 2019 - 06:58:52 PM »
    Quote from: 70chall440 on February 08, 2019 - 06:00:58 PM
    Thanks for the information I ordered a 15/16 MC from Dr. Diff so we will see how that works out.

    Good luck, that 1-1/32" bore is going to take quite a bit of effort to haul down. I've found the 15/16" to be a decent balance of pedal stroke and effort.
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    Build Page: Goody's 'Cuda Build Page
    1976 Dodge Warlock
    1972 Barracuda - 5.7 Hemi + T56 Magnum

    Wheel & Tire Specs:Link

    Offline 70chall440

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #8 on: February 09, 2019 - 12:05:12 AM »
    Quote from: GoodysGotaCuda on February 08, 2019 - 06:58:52 PM
    Good luck, that 1-1/32" bore is going to take quite a bit of effort to haul down. I've found the 15/16" to be a decent balance of pedal stroke and effort.

    Oh it is...  :bigsmile: Thats why I starting investigating it. It would stop but not without a lot of effort. Having the Viper calipers on the front with 13" rotors and Cobra calipers in the rear with 12" I figured it would have stopped much better. I thought I had a 15/16" MC in it, however as I stated in the initial post, its clear I didn't really do my home work and took something at face value rather than actually understanding what I had. I came upon an article online which listed casting numbers and that got me looking at mine. Although my casting number wasn't listed in the article, it got me looking harder at it and after some searching I found a thread on another forum where someone had the same one as I do asking about it, someone responded that it had a 1 1/32" bore. So here we are and now I will have a known entity.
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    Current Mopar
    70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
    05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
    Past Mopars
    9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

    Offline Kevin71

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #9 on: April 15, 2019 - 07:45:37 PM »
    What size wheels you run with those 13" disc?
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    Offline 70chall440

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #10 on: April 15, 2019 - 09:55:59 PM »
    17's
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    Current Mopar
    70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
    05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
    Past Mopars
    9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

    Offline jbaha

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #11 on: June 21, 2019 - 03:27:19 AM »
    Hey!

    I have also done a full disc brake conversion (06 mustang brakes)

    I have the original power-booster/proportioning valve. It's just lame with the new setup, I'm looking for a firm pedal feel... What works for you? Can i stay with power brakes or go manual?
    « Last Edit: June 21, 2019 - 03:48:13 AM by jbaha »
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    Offline 70chall440

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #12 on: June 21, 2019 - 11:40:41 AM »
    Yes you can have power, however you will need to change the MC for 4 wheel disc; that said I would try it with what you have and see how it is. Some people have said they didn't have any issues, however technically you need a different (smaller) MC. Also, the proportioning valve should be changed, but again some have reported they got away with using the stock one.
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    Current Mopar
    70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
    05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
    Past Mopars
    9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

    Offline Bucks70RT

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #13 on: July 27, 2019 - 09:26:53 PM »
    How did the 15/16 Dr diff master cylinder work out?
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    Offline 70chall440

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    Re: Let's talk brake master cylinders - Specifically for disc disc applications
    « Reply #14 on: July 28, 2019 - 12:01:07 PM »
    Ir definitely works better, I haven't driven it enough to really make a determination. I have manual brakes in my 52 as well and they work well but it has drums in the rear. Bottom line is that the 15/16 MC is much better than the larger one.
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    Current Mopar
    70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
    05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
    Past Mopars
    9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)
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