Master Cylinder Question

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colnago
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Master Cylinder Question

Post by colnago »

All,

Stupid question, but I'm gathering parts for a drum-to-disc conversion. I have 90% of the parts, and thought I could start putting things together, until I ran into problems finding pre-made hydraulic lines to run from the master cylinder to the proportioning valve. The MC has outlets of 9/16" front, and 3/8" rear. I think the large reservoir is in the rear. So, does the large reservoir, with the 3/8" fitting, go to the front (disc) brakes, and the small reservoir, with the 9/16" fitting, go to the rear (drum) brakes? Or vice-versa?

Thanks,

Joseph
"Sugar", my 1967 Ford F250 2WD Camper Special, 352FE, Ford iron "T" Intake with 1405 Edelbrock, Duraspark II Ignition, C6 transmission, front disc brake conversion.
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HIO Silver
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Re: Master Cylinder Question

Post by HIO Silver »

Large reservoir goes to the front because more fluid is required to move the caliper's pistons.
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colnago
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Re: Master Cylinder Question

Post by colnago »

Does it matter what size Lines I use between the MC and the proportioning valve? I wouldn't think so, since we're only talking a few inches to a few feet (depending on mounting location), and the metering valve is supposed to even out the front/back pressure, but I'd rather not find out by running into a tree when I go for my "test stop."

Joseph
"Sugar", my 1967 Ford F250 2WD Camper Special, 352FE, Ford iron "T" Intake with 1405 Edelbrock, Duraspark II Ignition, C6 transmission, front disc brake conversion.
ultraranger
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Re: Master Cylinder Question

Post by ultraranger »

The hardline should be 3/16" in diameter. Assuming all the air is out of a brake system, it wouldn't matter if one brake component was 5" from the MC and another was 50' from it. The pressure applied would be the same on both.

You can get brand new 7/16"-24, 1/2"-20 and 9/16"-18 fittings from Classic Tube that's designed to fit 3/16" brake tubing.

The metering valve will momentarily delay (hold off) pressure to the front brakes to give the rear brakes some time to overcome the tension of the retracting springs and to start moving the shoes towards the friction surfaces of the drums.

The proportioning valve will reduce the rate of pressure rise to the rear brakes, relative to what's being applied to the front brakes but, only in a situation where the brake system pressures are high --as in a panic stop. In all other cases during 'normal' driving, the proportioning valve remains completely open and does nothing.
Steve

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colnago
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Re: Master Cylinder Question

Post by colnago »

So, next dumb question. If all of the lines are 3/16", why are the outlets from the MC different sizes? Do some applications use different size lines between front and back?

Joseph
"Sugar", my 1967 Ford F250 2WD Camper Special, 352FE, Ford iron "T" Intake with 1405 Edelbrock, Duraspark II Ignition, C6 transmission, front disc brake conversion.
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Re: Master Cylinder Question

Post by ultraranger »

The O.D. of the fittings is different but the I.D. of the hole in the center is for 3/16" tubing. Most likely, your local parts stores won't carry the correct larger O.D. fittings with a 3/16" I.D. and they will point you to the fittings adapters bin. Classic Tube has the correct direct connection fittings.

The main purpose of the different fitting sizes is to keep a person from swapping up the lines and connecting them to the wrong ports.
Steve

1969 SWB F100 Ranger. 240-6, C-4, 9" N-case 31-spline Traction-Lok w/3.50 gears.

1968 Mustang. My high school car. Owned since 1982.

2003 Azure Blue Mustang Mach1.
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