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brake question #3229289 04/26/24 10:11 AM 04/26/24 10:11 AM
Joined: Mar 2005 Posts: 1,552 Michigan K Kiddart OP pro stock
Kiddart OP pro stock K Joined: Mar 2005 Posts: 1,552 Michigan	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

Re: brake question [Re: Kiddart] #3229300 04/26/24 11:12 AM 04/26/24 11:12 AM
Joined: Feb 2003 Posts: 8,671 A Andrewh master
Andrewh master A Joined: Feb 2003 Posts: 8,671	I have 4 wheel disc and don't have one. now having said that, it is supposed to be a safety item as well.

Re: brake question [Re: Kiddart] #3229359 04/26/24 06:36 PM 04/26/24 06:36 PM
Joined: Dec 2014 Posts: 5,818 ohio R ruderunner master
ruderunner master R Joined: Dec 2014 Posts: 5,818 ohio	Originally Posted by Kiddart 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

Re: brake question [Re: Andrewh] #3229360 04/26/24 06:38 PM 04/26/24 06:38 PM
Joined: Nov 2006 Posts: 4,757 Star Idaho 6 67vertman master
67vertman master 6 Joined: Nov 2006 Posts: 4,757 Star Idaho	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.

Re: brake question [Re: 67vertman] #3229377 04/26/24 08:52 PM 04/26/24 08:52 PM
Joined: Dec 2005 Posts: 11,569 Fulton County, PA C CMcAllister Mr. Helpful
CMcAllister Mr. Helpful C Joined: Dec 2005 Posts: 11,569 Fulton County, PA	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.

Re: brake question [Re: Kiddart] #3229385 04/26/24 10:34 PM 04/26/24 10:34 PM
Joined: Jan 2003 Posts: 15,362 Omaha Ne T TJP I Live Here
TJP I Live Here T Joined: Jan 2003 Posts: 15,362 Omaha Ne	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. www.tandmautomotive-omaha.com

Re: brake question [Re: CMcAllister] #3229409 04/27/24 06:25 AM 04/27/24 06:25 AM
Joined: Dec 2014 Posts: 5,818 ohio R ruderunner master
ruderunner master R Joined: Dec 2014 Posts: 5,818 ohio	Originally Posted by CMcAllister 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, This is all true. Starting completely from scratch and designing and specifying every aspect means you can do it without any proportioning valve. Think OEM research and development. But, we're limited to what's available and it's going to be less than ideal. I recommend installing an adjustable valve from the start. Due to the differences in operating pressures, a disc drum system needs one no matter how much math and research you do. Angry white pureblood male

Re: brake question [Re: 67vertman] #3229410 04/27/24 06:29 AM 04/27/24 06:29 AM
Joined: Dec 2014 Posts: 5,818 ohio R ruderunner master
ruderunner master R Joined: Dec 2014 Posts: 5,818 ohio	Originally Posted by 67vertman 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. Originally a 4 wheel drum or disc drum? If Originally a disc drum setup, you're leaving alot of rear braking power unused. If drum drum, you're good. Angry white pureblood male

Re: brake question [Re: ruderunner] #3229537 04/27/24 03:47 PM 04/27/24 03:47 PM
Joined: Jan 2003 Posts: 25,802 Rio Linda, CA John_Kunkel Too Many Posts
John_Kunkel Too Many Posts Joined: Jan 2003 Posts: 25,802 Rio Linda, CA	Originally Posted by ruderunner A proportioning valve is needed for disc drum systems. It's not required for drum drum or disc disc. And, yet, the factory often uses them in disc/disc installations. IMO, the only way to know is actual testing...slam on the brakes at speed and see what happens. The INTERNET, the MISinformation superhighway

Re: brake question [Re: John_Kunkel] #3229598 04/27/24 10:12 PM 04/27/24 10:12 PM
Joined: Jan 2003 Posts: 15,362 Omaha Ne T TJP I Live Here
TJP I Live Here T Joined: Jan 2003 Posts: 15,362 Omaha Ne	Originally Posted by John_Kunkel Originally Posted by ruderunner A proportioning valve is needed for disc drum systems. It's not required for drum drum or disc disc. And, yet, the factory often uses them in disc/disc installations. IMO, the only way to know is actual testing...slam on the brakes at speed and see what happens. 100% www.tandmautomotive-omaha.com

Re: brake question [Re: TJP] #3229622 04/27/24 11:53 PM 04/27/24 11:53 PM
Joined: Dec 2005 Posts: 11,569 Fulton County, PA C CMcAllister Mr. Helpful
CMcAllister Mr. Helpful C Joined: Dec 2005 Posts: 11,569 Fulton County, PA	Originally Posted by TJP Originally Posted by John_Kunkel Originally Posted by ruderunner A proportioning valve is needed for disc drum systems. It's not required for drum drum or disc disc. And, yet, the factory often uses them in disc/disc installations. IMO, the only way to know is actual testing...slam on the brakes at speed and see what happens. 100% All true. However, I would drive it first and see what is needed, or not...and where. If the results don't match the theory, change the theory.

Re: brake question [Re: John_Kunkel] #3229641 04/28/24 07:56 AM 04/28/24 07:56 AM
Joined: Dec 2014 Posts: 5,818 ohio R ruderunner master
ruderunner master R Joined: Dec 2014 Posts: 5,818 ohio	Originally Posted by John_Kunkel Originally Posted by ruderunner A proportioning valve is needed for disc drum systems. It's not required for drum drum or disc disc. And, yet, the factory often uses them in disc/disc installations. IMO, the only way to know is actual testing...slam on the brakes at speed and see what happens. Why not include the entire statement. I did say it's good to have for fine tuning. Angry white pureblood male

Re: brake question [Re: ruderunner] #3229670 04/28/24 09:38 AM 04/28/24 09:38 AM
Joined: Oct 2005 Posts: 8,872 Ontario, Canada S Stanton Don't question me!
Stanton Don't question me! S Joined: Oct 2005 Posts: 8,872 Ontario, Canada	quote] I did say it's good to have for fine tuning.[/quote] And the tune will change between a full tank and an empty tank. Unfortunately there is no “automatic” prop valve. Many drag racers put the valve in the front brake line. An average street car should have it in the rear line. Race cars - other than drag cars - will have two masters with the bias adjustable in the linkage so adjustment can be done on the fly as conditions dictate.

Re: brake question [Re: Stanton] #3229687 04/28/24 10:44 AM 04/28/24 10:44 AM
Joined: May 2019 Posts: 6,253 nowhere S Sniper master
Sniper master S Joined: May 2019 Posts: 6,253 nowhere	Originally Posted by Stanton And the tune will change between a full tank and an empty tank. Unfortunately there is no “automatic” prop valve. Yes there is. My turbo minivan had one. Will it work on our stuff? Dunno.

Re: brake question [Re: Sniper] #3229700 04/28/24 11:39 AM 04/28/24 11:39 AM
Joined: Sep 2003 Posts: 19,406 north of coder moparx "Butt Crack Bob"
moparx "Butt Crack Bob" Joined: Sep 2003 Posts: 19,406 north of coder	Originally Posted by Sniper Originally Posted by Stanton And the tune will change between a full tank and an empty tank. Unfortunately there is no “automatic” prop valve. Yes there is. My turbo minivan had one. Will it work on our stuff? Dunno. i was just going to mention that as well, but you treed me............ all the minivans i have owned or junked over the years has had one of those things. also wondered if adding one would work in other applications.

Re: brake question [Re: moparx] #3229740 04/28/24 02:05 PM 04/28/24 02:05 PM
Joined: Dec 2014 Posts: 5,818 ohio R ruderunner master
ruderunner master R Joined: Dec 2014 Posts: 5,818 ohio	Those have been used on lots of different vehicles over the years. Problem is they're typically designed for a specific vehicle and the odds that they will be close for our stuff are slim. Plus, they're all old. Pretty much disappeared when ABS became common. Angry white pureblood male

Re: brake question [Re: ruderunner] #3229944 04/29/24 12:00 PM 04/29/24 12:00 PM
Joined: Oct 2004 Posts: 2,820 Connecticut FurryStump master
FurryStump master Joined: Oct 2004 Posts: 2,820 Connecticut	Make sure if you are running a disc/drum master cylinder on a disc/disc setup. There isn’t a residual valve hiding in the rear brake port. Ask me how long I ran with one hiding in my port…… best of 11.39 at 117 mph 1.60 60’. 68 340 S Barracuda Fastback F.A.S.T [IMG]http://i67.tinypic.com/2mnnnnt.jpg[/IMG]

Re: brake question [Re: Sniper] #3229954 04/29/24 12:26 PM 04/29/24 12:26 PM
Joined: Jan 2003 Posts: 75,012 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,012 U.S.S.A.	Originally Posted by Sniper Originally Posted by Stanton And the tune will change between a full tank and an empty tank. Unfortunately there is no “automatic” prop valve. Yes there is. My turbo minivan had one. Will it work on our stuff? Dunno. Also used on various 80's/90's pickups with rear wheel only ABS . running up my post count some more .

Re: brake question [Re: FurryStump] #3230088 04/29/24 10:42 PM 04/29/24 10:42 PM
Joined: Jan 2003 Posts: 15,362 Omaha Ne T TJP I Live Here
TJP I Live Here T Joined: Jan 2003 Posts: 15,362 Omaha Ne	Originally Posted by FurryStump Make sure if you are running a disc/drum master cylinder on a disc/disc setup. There isn’t a residual valve hiding in the rear brake port. Ask me how long I ran with one hiding in my port…… There is also the disc / disc master on a disc drum setup that will wreak havoc. That can be cured with an inline residual valve to the rears www.tandmautomotive-omaha.com

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