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brake question
#3229289
04/26/24 10:11 AM
04/26/24 10:11 AM
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Joined: Mar 2005
Posts: 1,550
Michigan
Kiddart
OP
pro stock
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OP
pro stock
Joined: Mar 2005
Posts: 1,550
Michigan
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I have a question; it might be controversial but i still have it. I was reading i think on here and can't find the thread. If you have a modern master cylinder from a mid 80s pickup in an older car do you need to run a proportioning valve? If i recall, there were a few guys saying with 4-wheel disc setup and new master cylinder the prop valve renders its self-useless?? I did a 4-wheel disc setup on my demon and just wondering as I will be doing a line lock and if i can get rid of the prop valve I will.
True or false? and any comments or experience is welcome.
I know I ask a lot of questions i should know the answers to.
Thank you
Kiddart
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Re: brake question
[Re: Kiddart]
#3229359
04/26/24 06:36 PM
04/26/24 06:36 PM
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Joined: Dec 2014
Posts: 5,778
ohio
ruderunner
master
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master
Joined: Dec 2014
Posts: 5,778
ohio
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I have a question; it might be controversial but i still have it. I was reading i think on here and can't find the thread. If you have a modern master cylinder from a mid 80s pickup in an older car do you need to run a proportioning valve? If i recall, there were a few guys saying with 4-wheel disc setup and new master cylinder the prop valve renders its self-useless?? I did a 4-wheel disc setup on my demon and just wondering as I will be doing a line lock and if i can get rid of the prop valve I will.
True or false? and any comments or experience is welcome.
I know I ask a lot of questions i should know the answers to. A proportioning valve is needed for disc drum systems. It's not required for drum drum or disc disc. It would be beneficial in those cases for fine tuning though. BTW, that 80s truck MC has 2 problems with disc disc systems. 1 it may have a residual pressure valve, no bueno for disc brakes. 2 the reservoir for the rear brakes is much smaller than typically found on disc brakes, if you keep an eye on fluid levels this isn't a problem.
Angry white pureblood male
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Re: brake question
[Re: Andrewh]
#3229360
04/26/24 06:38 PM
04/26/24 06:38 PM
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Joined: Nov 2006
Posts: 4,721
Star Idaho
67vertman
master
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master
Joined: Nov 2006
Posts: 4,721
Star Idaho
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I have four wheel disc brakes on my 70 E Body, I installed a disc brake master cylinder and I am still running the proportioning valves. No issues after 12 years. I think you can do without it though.
My Monster are real!
Living within your means makes life pretty easy.
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Re: brake question
[Re: 67vertman]
#3229377
04/26/24 08:52 PM
04/26/24 08:52 PM
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Joined: Dec 2005
Posts: 11,531
Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,531
Fulton County, PA
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Just throwing a mix of parts together and the answer is "maybe". I always considered them a bandaid. Sometime a necessary one, but still a bandaid.
Figuring out pedal ratios, bore sizes of the MC and the calipers along with the number of pistons to get total area of the bores, tire sizes (big tire drag car vs all tires relatively the same size), getting it all right, and putting it all together and it should not be needed,
If the results don't match the theory, change the theory.
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Re: brake question
[Re: Kiddart]
#3229385
04/26/24 10:34 PM
04/26/24 10:34 PM
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Joined: Jan 2003
Posts: 15,313
Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,313
Omaha Ne
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You won't know for sure what you need until you install and test it. There are a ton a variables involved that cannot be assumed or guessed at. pedal ratio, piston sizes, drum and disc sizes, vehicle weight, brake lining friction coefficient, tires sizes, their compounds and the list goes on. You will likely need the residual pressure valves as previously mentioned You can install an adjustable if your replumbing the rears or roll the dice and see if you need one  
Last edited by TJP; 04/26/24 10:36 PM.
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