how do i calculate the pedal ratio on this ODD setup?

[Bad94]

this is a new one for me. its off a 1956 Continental Mark II

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from the way it looks when moving the pedal that second linkage reduces the pedal ratio.

for the pedal itself it looks like or is real close to 18.5 as the the overall length and 5.125 pivot length. my math tells me its a about a 3.60:1 ratio
the second linkage is 5.5O AL and 2.5 pivot length. im getting 2.2:1 on that one.

so do i divide those or subtract those to get the actaul ratio the pushrod moves vs. the pedal pad. either way im getting a really low # like 1.something and that makes sence just by moving the pedal and watching how everything moves. ive even gone as far as drawing everything full scale in card board and making links out of cardboard just to see wha tit takes to get a more normal pedal ratio.

here's another kicker, this "bolt on" kit came with a booster mount that has another extra link that my brain is telling me it would further reduce the pedal ratio. its layout is similar to that second link above. the booster goes to the outter hole.

the company this came from seems to be more confused than i am and im not even gonna get into the actual disc kit that goes onto the spindle right now.

whats a good pedal ratio to have its a 8" dual booster and the car is about 5000lbs. 4:1 enough or should i go higher.

[dontlifttoshift]

Easily one of the top ten best looking cars ever manufactured in the U.S.

Can you eliminate all the bell cranks and run straight to the booster with a pushrod? I am guessing the new booster brackets are like the tri five conversions that move the booster up for valve cover clearance so not likely you can run straight.

Ratio really depends on master bore and piston size at the calipers and or drums. 4 to 1 with a dual diaphragm booster and an 1 1/8" master with rear drums and the pedal will be like an on/off switch with no "modulation" in between.

[Bad94]

Easily one of the top ten best looking cars ever manufactured in the U.S.

Can you eliminate all the bell cranks and run straight to the booster with a pushrod? I am guessing the new booster brackets are like the tri five conversions that move the booster up for valve cover clearance so not likely you can run straight.

Ratio really depends on master bore and piston size at the calipers and or drums. 4 to 1 with a dual diaphragm booster and an 1 1/8" master with rear drums and the pedal will be like an on/off switch with no "modulation" in between.

you were somebody if you drove one in '56 power everything

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is this the booster bracket your talking about? its not a real good pic but i already had it on the computer. you can see the booster rod is higher than the rod coming from under the dash.

whats the real point to a bracket with a linkage on it like that? take a manual pedal with a high ratio like 7:1 and lower it down to something more normal for a power application?

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i think i can go straight to the pedal with out any other linkage stuff but what ratio would you suggest? 5:1 or there abouts would be real close to the center of the hole already in the firewall.

[Bryce]

this is a new one for me. its off a 1956 Continental Mark II

53848

53849

53850


from the way it looks when moving the pedal that second linkage reduces the pedal ratio.

for the pedal itself it looks like or is real close to 18.5 as the the overall length and 5.125 pivot length. my math tells me its a about a 3.60:1 ratio
the second linkage is 5.5O AL and 2.5 pivot length. im getting 2.2:1 on that one.

so do i divide those or subtract those to get the actaul ratio the pushrod moves vs. the pedal pad. either way im getting a really low # like 1.something and that makes sence just by moving the pedal and watching how everything moves. ive even gone as far as drawing everything full scale in card board and making links out of cardboard just to see wha tit takes to get a more normal pedal ratio.

here's another kicker, this "bolt on" kit came with a booster mount that has another extra link that my brain is telling me it would further reduce the pedal ratio. its layout is similar to that second link above. the booster goes to the outter hole.

the company this came from seems to be more confused than i am and im not even gonna get into the actual disc kit that goes onto the spindle right now.

whats a good pedal ratio to have its a 8" dual booster and the car is about 5000lbs. 4:1 enough or should i go higher.

It looks like the pedal to brake movement is 3.6/2.2:1 or 1.6:1. stock did it have a huge booster?

How much engine vacuum do you have? lets say 10psi

area of a 8" booster is 4x4x3.14=50.24 in^2

PSI is pounds per in^2 so 50.24in^2 x 10 psi is 502.4lbs of force pusing on the brake this added to the force applied to the pedal times the pedal ratio. If the ratio is 1.6:1 and you push 100lbs then the total force on the MC is 662.4lbs. what is you piston diameter? If it is 1" then the line pressure at the MC is 662.4lbs/.785 = 844psi. a 7/8 piston would yield a line pressure of 1103psi.

[dontlifttoshift]

If you can run the pushrod straight off the pedal and get 5 to 1 on the pedal you should be good to go.....I think. That's what I would do.

What bore Master did they send you?

**edit**

Looked at the pics again. The new assembly is on the left, correct? So there is a new bellcrank with the new booster then. Do you still need the bell crank from the picture in your first post?

[Bad94]

It looks like the pedal to brake movement is 3.6/2.2:1 or 1.6:1. stock did it have a huge booster?

How much engine vacuum do you have? lets say 10psi

area of a 8" booster is 4x4x3.14=50.24 in^2

PSI is pounds per in^2 so 50.24in^2 x 10 psi is 502.4lbs of force pusing on the brake this added to the force applied to the pedal times the pedal ratio. If the ratio is 1.6:1 and you push 100lbs then the total force on the MC is 662.4lbs. what is you piston diameter? If it is 1" then the line pressure at the MC is 662.4lbs/.785 = 844psi. a 7/8 piston would yield a line pressure of 1103psi.

so i divide the two ratios to get the final ratio?

wont the pedal be ultra sensitive with only a 1.6:1?

who would a dual diaphragm affect things? double the area?

the stock booster master combo is like nothing ive ever seen.


If you can run the pushrod straight off the pedal and get 5 to 1 on the pedal you should be good to go.....I think. That's what I would do.

What bore Master did they send you?

**edit**

Looked at the pics again. The new assembly is on the left, correct? So there is a new bellcrank with the new booster then. Do you still need the bell crank from the picture in your first post?

yes new bellcrank with the new booster/bracket its a 1.625 ratio. id like to avoid using the bellcrank on the stock pedal. it seems to be making things much more difficult.

i think i could use the new bellcrank if i had to. ill have to flip the bracket over though. in the up (booster raised from the engine) it hits the hood.

ill measure the caliper dia. and master dia. and report back. ill get some pics bo the old booster too

thanks for all the help guys.

[Bryce]

so i divide the two ratios to get the final ratio?

wont the pedal be ultra sensitive with only a 1.6:1?

Yes and yes



who would a dual diaphragm affect things? double the area?



I believe it would.

[Bad94]

the master cylinder has a 1" bore, the caliper has a single 2.370" piston, rotor OD is 11.75"

so with a 5:1 pedal ratio id have 1000lbs of line pressure?

here is the bellcrank that came with the new booster bracket. the pushrod on the booster goes in the hole at 3.25"
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here are some pics of the stock booster
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[Bad94]

just to keep this updated ive got some different booster brackets on the way