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hi does any one know how much psi a front master/c makes[gl1100]
 

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I've never measured it... but just from some mechanical advantage leverage calculations.. probably something on the order of 1200 - 1500 psi would be possible, maybe more if you had an exceptionally strong grip...
 

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I'm interested to know why you are trying to get this info. are you looking at changing the front brakes?
 

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there's a simple formula I don't remember
 

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To calculate the pressure in the caliper piston and from that the pressure of the pad against the disk measure the ratio of the area of the master cylinder bore vs the caliper bore... Multiply that psi by the ratio of the master cylinder piston face area vs two times the caliper piston face area and you'd have the pressure the two pistons were exerting on the brake pad.

Thought that's what I said, I didn't mention how to compute the areas because that's basic arithmetic. You do need to take into consideration the mechanical advantages of the master cylinders which the simple comparison of master and slave cylinders don't account for.
 

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exavid wrote:
To calculate the pressure in the caliper piston and from that the pressure of the pad against the disk measure the ratio of the area of the master cylinder bore vs the caliper bore. Measure the distance from the brake pedalor lever's midsectionto it's pivot point. Then measure the distance from the pivot to the point the lever or pedal hits the master cylinder piston. Calculate the ratio of the twodistances. Next you'd have to estimate or use a scale to measure the pressure you're putting on the pedal or lever. Once you know how much pressure you're applying to the lever or pedal multiply that by the ratio of the mechanical advantage from the lever to the master cylinder piston. The result of that needs to be multiplied by the area of the master cylinder piston face resulting in psi applied to the master cylinder. Multiply that psi by the ratio of the master cylinder piston face area vs two times the caliper piston face area and you'd have the pressure the two pistons were exerting on the brake pad.

Since you have a large mechanical advantage with the lever or pedal pressing on the small master cylinder piston and since the small piston forcing fluid into the larger bored caliper cylinde there's another impressive mechanical advantage it would be easy to increase the forty or so pounds on the brake pedal to over 1000psi at the caliper. Your grip on the front brake lever is weaker than the power you can develop with your foot on the pedal but the mechanical advantage of the lever to the master cylinder is greater which helps multiply the force. Those brake hoses are strong and cord lined to withstand the pressures put on them but you can see them flex when you hit the brakes.
Hey Paul.. Thanks for taking the time to write it.. I was a little lazy (but that is why you get top poster)... still should be about 1200 to 1500 psi:cooldevil:
 

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That sounds like the right ball park to me, wish I had a pressure gauge high enough to find out. Might be able to calibrate it from 'Weakling' to 'Superman' to test your grip while you ride.
 

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exavid wrote:
That sounds like the right ball park to me, wish I had a pressure gauge high enough to find out. Might be able to calibrate it from 'Weakling' to 'Superman' to test your grip while you ride.
I thought about doing that too.. but it would take a pretty "stiff" gage to be able to do it.. the typical bourdon gage will have too much displaced volume.. you'd bottom out (maybe you could pump it??).. a solid state piezio(sp?)-electric would work..
 

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hi i was only asking as i been looking at a universal master/cly with a operating pressure of MPa? any one know want that means. thanks mark.
 

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mark3 wrote:
hi i was only asking as i been looking at a universal master/cly with a operating pressure of MPa? any one know want that means. thanks mark.
1 megapascal (Mpa)= 145.037738 pounds per square inch (psi)
 

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mark3 wrote:
would it be ok on a gl1100 std ?
I have no idea what you are considering.... why can't you rebuild what you have?
 

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C"mon Mark3...you"re going to put air brakes on the Goldwing aren"t you ???? When you pull up at the lights it goes "SSSHHHHH"
 

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The ratio would actually be the "area" of the cross-section bore.

Area = pie * radius squared

A = 3.14 * r^2 or A = 3.14 * (diam/2)^2

If you have dual pistons in the caliper, the pressure on the pads would be doubled.

On integrated rear brake (rear and front combo),the line pressure is equal throughout, but the caliper boresand pressure on thepadswould bedifferent.
 

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sandiegobrass wrote:
exavid wrote:
To calculate the pressure in the caliper piston and from that the pressure of the pad against the disk measure the ratio of the area of the master cylinder bore vs the caliper bore. Measure the distance from the brake pedalor lever's midsectionto it's pivot point. Then measure the distance from the pivot to the point the lever or pedal hits the master cylinder piston. Calculate the ratio of the twodistances. Next you'd have to estimate or use a scale to measure the pressure you're putting on the pedal or lever. Once you know how much pressure you're applying to the lever or pedal multiply that by the ratio of the mechanical advantage from the lever to the master cylinder piston. The result of that needs to be multiplied by the area of the master cylinder piston face resulting in psi applied to the master cylinder. Multiply that psi by the ratio of the master cylinder piston face area vs two times the caliper piston face area and you'd have the pressure the two pistons were exerting on the brake pad.

Since you have a large mechanical advantage with the lever or pedal pressing on the small master cylinder piston and since the small piston forcing fluid into the larger bored caliper cylinde there's another impressive mechanical advantage it would be easy to increase the forty or so pounds on the brake pedal to over 1000psi at the caliper. Your grip on the front brake lever is weaker than the power you can develop with your foot on the pedal but the mechanical advantage of the lever to the master cylinder is greater which helps multiply the force. Those brake hoses are strong and cord lined to withstand the pressures put on them but you can see them flex when you hit the brakes.
Hey Paul.. Thanks for taking the time to write it.. I was a little lazy (but that is why you get top poster)... still should be about 1200 to 1500 psi:cooldevil:
You guys paid attention in grade 10 physics classes.:cool:
 

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Foosman(5) wrote:
The ratio would actually be the "area" of the cross-section bore.

Area = pie * radius squared

A = 3.14 * r^2 or A = 3.14 * (diam/2)^2

If you have dual pistons in the caliper, the pressure on the pads would be doubled.
Note highlighted areas of post above, I think I said that with the exception of the formula for the area of a circle which I'd think was known to all.
 

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I see it now, but the issue was distance vs area as written. You can still have a ratio either or any two numbers.

Many people can not even add two numbers.

The comparison would have be like apples and oranges. The use of the distance comparison would be "linear" where as a squared function is "non-linear"

I.E. Doubling the distance of a diameter or radius does not double the area.

Let's have someone do the calculations for the mechanical leverage, psi, and pressure on the pads. I will be in St. Louis.
 

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Yep the distances have to be considered to determine the leverage or mechanical advantage which determines the pressure or effort applied to the master cylinder to start the whole shebang off.
 
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