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disc / disc brake plumbing help

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Speedy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedy Quote  Post ReplyReply Direct Link To This Post Topic: disc / disc brake plumbing help
    Posted: 11 June 2021 at 7:55pm
so I am getting ready to do my brake lines.
I am running herms dual master
pv4c proportioning valve
and dana 30 caliper disc front
k10 caliper disc rear

I searched allot and seems like everyone runs 3/16 line all around.

I am wondering should 1/4 from the master cylinder to the proportioning valve (both circuit lines)
then run the 3/16 on both the outs on the front of the proportioning valve (assuming I can use both)

then run 1/4 to the rear then split to 3/16

to possibly further complicate things, can I run two flex hoses front the caliper to the frame rail like a modern setup on the rear and front.
IF so, I would just purchase a T to transition the 1/4 to 3/16 line somewhere at the rear crossmember.

trying to get it right the first time around so figured I could ask if anyone has disc disc setup and what works.


Edited by Speedy - 11 June 2021 at 7:56pm
- Mike
47 CJ2A - Warn OD, Ramsey PT1-J/Koenig 100,Arctic top,Dana 44 30 spline full float with disc's,Dana 30 with discs, 2.5 lift, Saginaw power steering, dual master cylinder
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rus Curtis Quote  Post ReplyReply Direct Link To This Post Posted: 11 June 2021 at 9:55pm
From the vehicles I've worked on, I've only seen 3/16" brake lines.  My jeep has 1/4" gas lines.



Rus Curtis
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Post Options Post Options   Thanks (0) Thanks(0)   Quote duffer Quote  Post ReplyReply Direct Link To This Post Posted: 11 June 2021 at 10:33pm
I'm using the Scout II discs up front, the D30 discs on the rear, Wilwood proportioning valve and master cylinder, all plumbed with 3/16's.  I ran D30 discs on both ends for 30 something years with the same size lines.  3/16" is all you need.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nofender Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2021 at 6:26am
As others have stated, I can't see any value in going 1/4 inch. 

As for the soft lines at each corner - sure there is no issue doing that. Just make sure you use a line long enough to match your suspension travel. 

Me - I use a flexible line dropped to the center of the axle. Then flex lines at each wheel. This way suspension travel isn't an issue at all. 

No real wrong path to take. It's a matter of preference and matching your set up with the best options. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OnlyOneDR Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2021 at 10:15am
Pretty much all cars and light trucks use 3/16" lines. There is no value to going with a larger line.   Ideally you want the smallest lines possible to minimize the ability of the lines to swell so you have good hard brakes. Larger lines mean more surface area to stretch and more fluid to compress. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedy Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2021 at 12:08pm
thanks everyone.
3/16 it is.

all the orifices match 3/16, except the proportioning valve for the rear is 1/4 so threw me off.

I am now wondering if possibly I can tell if my MC is for disc/disc?
ordered the parts so long ago and don't see any part numbers or info on the receipt 

or can anyone suggest what MC is best?  running herms bracket.

any terminal block I can use for the rear to split to two lines (maybe the stock diff housing T will work)

and if its a stretch, if anyone knows what flex lines can work coming down from the frame to the caliper. running a 2.5'' lift.   (I will investigate chev 1/2 ton lines)

however, I will give the rear caliper flex lines to frame some thought. maybe sticking to the stock setup is best.  one line coming down from the centre 


Edited by Speedy - 12 June 2021 at 12:25pm
- Mike
47 CJ2A - Warn OD, Ramsey PT1-J/Koenig 100,Arctic top,Dana 44 30 spline full float with disc's,Dana 30 with discs, 2.5 lift, Saginaw power steering, dual master cylinder
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