s550 brembo upgrade brake bias

thornclaw

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hello
there has been some concern about what happens to brake bias if you upgrade the 4 piston 14" factory gt brakes to the 6 piston 15" brembos. using some info from other posts i managed to come up with a calculation. the force applied to the pad via the caliper piston is the piston area x brake fluid psi. example: if you had 1 in squared piston area and applied 10 psi of brake fluid pressure you would have 10 pounds of force applied to the pad (10 psi x 1). if you had 2 inch squared of piston area and applied the same 10 psi of brake fluid pressure you would have 10 x 2= 20 pounds of force applied to the pad. the piston area of the brembos as measured by another forum member is 4.7% less than the factory gt brakes, meaning you would have 4.7% less total force applied to the pads. However, the rotor diameter is one inch larger, meaning the torque is increased by roughly 7% thereby increasing your overall braking force. the net result should be an increase, albeit small, of bias to the FRONT brakes. Other members feel free to check my math.
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Norm Peterson

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I think you should be making your corrections for rotor size based on mean pad radius from the center of the axle/stub axle..

Diameter of swept area on the rotor divided by two, minus half of pad width. Do this for both systems being compared, noting that pad widths will not necessarily be the same.

Braking torque needs to consider the friction over the entire pad width, not just at the outer edge.


Norm
 

Chef jpd

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How.do you decide what cereal to eat in the morning?

Seriously, many of us have done a 6 pot upgrade with absolutely no issues.

Norm, nice gasoline on the fire!!!!!
 
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thornclaw

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I think you should be making your corrections for rotor size based on mean pad radius from the center of the axle/stub axle..

Diameter of swept area on the rotor divided by two, minus half of pad width. Do this for both systems being compared, noting that pad widths will not necessarily be the same.

Braking torque needs to consider the friction over the entire pad width, not just at the outer edge.


Norm
i think you are right. does anyone have this data. i already threw out my old rotors.
but i think you would not need to change the master cylinder to do this upgrade.
regarding my cereal choice in the morning i employ a complex algorithm taking account cereal type, how much milk is left, number of eggs left in carton, time of day and what else is available
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BmacIL

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i think you are right. does anyone have this data. i already threw out my old rotors.
but i think you would not need to change the master cylinder to do this upgrade.
regarding my cereal choice in the morning i employ a complex algorithm taking account cereal type, how much milk is left, number of eggs left in carton, time of day and what else is available
regards
Yes, I have a full worksheet with all of the data. The end result is a 0.1% change in overall brake bias. The PP MC merely changes the required force at the pedal to induce the same pressures in the system.
 

Norm Peterson

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Norm, nice gasoline on the fire!!!!!
If you're going to run numbers to justify anything like this - even if it's only for personal understanding of what's happening in general terms - you're trying to be an engineer. And you need to build a sufficiently accurate mathematical model for your analysis, which may need to be done in somewhat finer detail than what a quick glance at the problem suggests. This is where engineering experience comes in; recognizing what could have significant effect isn't inherently the way most people look at things.


Oh, yeah . . . I just grab the box out of the cabinet.


Norm
 
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thornclaw

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If you're going to run numbers to justify anything like this - even if it's only for personal understanding of what's happening in general terms - you're trying to be an engineer. And you need to build a sufficiently accurate mathematical model for your analysis, which may need to be done in somewhat finer detail than what a quick glance at the problem suggests. This is where engineering experience comes in; recognizing what could have significant effect isn't inherently the way most people look at things.


Oh, yeah . . . I just grab the box out of the cabinet.


Norm
i came up with this calculation after eating a box of wheaties
 
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