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Question about dual master cylinders...


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Mike, there is just one MC for the front and one for the rear. The third one is for the clutch. ;)

:ugg: Oh.....

 

As for adjusting brake bias, I have seen a couple of guys with GT-40 kit cars that have set up a tunable adjustment dial on the center console. I think that reaching down there while moving might be a bad idea.

 

Cockpit Adjustable Proportioning Valve here... http://www.arizonazcar.com/brake.html

 

propv.jpg

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That's a different kind of prop valve. The one for the dual masters is the big red knob next to the gearshift. pkramer1.jpg

It doesn't attach to the brake line, it changes the bias at the master cylinder pushrod. Here's a description of how it works:

http://www.wilwood.com/Products/005-PedalAssemblies/Pages/techtip/pedaltech.asp

 

You can see that this guy has a prop valve plumbed into the brake line as well. You can super fine tune the brakes by using both types of valves.

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Is there really two adjustable prop valves in line in the picture above? Someone has really screwed up the balance between the calipers and MC if two adjustable prop valves are needed. Maybe one of those is a line lock used as a rear e-bake?

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No by pedal ratio I mean where you put the balance bar. On a car wtih a vacuum booster it needs to go a little higher up the arm. I looked at the tilton pedals and used there leverage ratio when I modded the stock arm (distance from pivot to balance bar and total length of pedal). I have driven a car with the balance bar in the stock location and it requires a lot higher pedal effort to get stopped.

 

Cary

 

At the risk of sounding like a complete idiot, I have to disagree. By lowering the master attachment point, the amount leverage is being decreased exponentially. Was the other car you drove a Z, with the same size masters, etc?

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It's not exponentially decreased. The ratio is explained here. http://www.wilwood.com/Products/005-PedalAssemblies/Pages/techtip/pedaltech.asp What will matter is that the higher the ratio the less throw on the master for a given amount on the pedal. So I guess you have to keep in mind how long the throw on the cylinder is and how long the throw is where you plan to install the pivot.

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At the risk of sounding like a complete idiot, I have to disagree. By lowering the master attachment point, the amount leverage is being decreased exponentially. Was the other car you drove a Z, with the same size masters, etc?

 

I raised them about a half inch. I don't really know why they look so low in the photos.

 

Cary

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It's not exponentially decreased. The ratio is explained here. http://www.wilwood.com/Products/005-PedalAssemblies/Pages/techtip/pedaltech.asp What will matter is that the higher the ratio the less throw on the master for a given amount on the pedal. So I guess you have to keep in mind how long the throw on the cylinder is and how long the throw is where you plan to install the pivot.

 

Ok, exponentially wasn't the right word, but it certainly is multiplied. That link only reinforces my statement. Technically one would want the attachment point as high as the pedal throw will allow, and this will also decrease the amount of pressure needed.

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well i'm giving this one a shot guys. here's a couple pics of the progress Ive made so far. there's a couple reasons i did this. first being that i need more room for how i want to package my turbo/wastegate. second, is that this is going to cost me about the same as restoring the stock system.[new masters/booster, mine were junk] and i've got another pedal box so if i screw up, i'm not ...screwed. to be honest i dont totally understand yet how these are supposed to better for performance braking, so i'll let one of you guys tell me that.

 

oh yeah, and i think they look cool.

 

everything came today. balance bar, remote adjuster, [1] 5/8" master and [1] 3/4" master, all wilwood . here it all is, along with my partly notched pedal box.

Dualmasters1002.jpg

 

close up of the parts.

 

Dualmasters1001.jpg

 

the first thing i did was notch the pedal box, for clearance of the balance bar. i made sure before i cut, that the masters would have enough throw. i still have to do a bit on the inside wall. after notching the pedal box, was do some measuring as to where these things were going to go. here is what i came up with. an interesting thing i found out was that the wilwood masters lined up perfectly in the stock holes for the clutch master cylinder. [is this some kind of industry wide bolt pattern? or are we just lucky?] i guess i'll be picking up another one, just for continuity's sake.

 

dualmastercyllinderpattern.jpg

 

after that was cutting a hole in the pedal to fit the balance bar. this was by far the hardest part, it took about an hour. all i used was a drill and a round file.

 

dualmasterpedal001.jpg

 

close up

 

dualmasterpedal002.jpg

 

not welded yet.

 

so next is cutting off the old front, and making a new one for the masters to go through. i should get to that within a few days...

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The benefit to this over a normal master with a proportioning valve is that this is ACTUALLY proportional and a valve really isn't, so you can get more rear braking (especially at high speeds) with this setup than you can with a traditional prop valve.

 

I've decided that I'm going to do the same. Keep updating as it comes along. You'll probably save me some hassle... :wink:

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did some more work today. got the sleeve for the balance bar welded in, cut up the pedal box some more, and got the replacement face welded partway in. i'm takin a break right now. i'll update some more if i get anything else done tonight.

 

the hole near the weld is for the return spring

 

DualMasterCylinderFab005.jpg

 

DualMasterCylinderFab006.jpg

 

here you can see the clearance with the interior wall. it's fine if i keep the balance bar in the middle, but if i'm going to need to adjust it further that way i'll have to cut out a slot

 

DualMasterCylinderFab007.jpg

 

DualMasterCylinderFab009.jpg

 

DualMasterCylinderFab011.jpg

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Just finished! Kinda. just a few more things to button up.

 

DualMasterCylinderFab012.jpg

 

DualMasterCylinderFab013.jpg

 

DualMasterCylinderFab014.jpg

 

DualMasterCylinderFab015.jpg

 

the only issue now is that the holes in the plate are a little far apart, and they're a LITTLE crooked. not sure how to real with that yet. maybe spacers to push the arms further apart on the balance bar.

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What are the washers supposed to do? From your pics it's not clear what you're trying to do here. You need to clearance the inside of the bolt above and I would recommend adding the lip back in around the firewall mount as it adds stiffness.

 

Cary

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I think he mounted the masters too far apart, so the washers are spacing the black parts (don't know the name of those) so that the rod from them to the masters are straight.

 

Thats exactly right. The balance bar had 1 very thin washer on each side of the middle tube that welds into your pedal. i used some thicker ones to space the black blocks out more so they would line up again. if this ends up not giving me enough adjustment i'll try to replace the main threaded rod with a longer one. i should be able to because the monoball is just held in with jam nuts.

 

i dont see how that would make them work any differently.

 

Adding bracing is one of things i haven't gotten to yet. i was planning on adding the lip back, and triangulating it back to the main body...kinda hard to explain, you'll see.

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