Dean,
Your replies are sounding more and more defensive. This is not an attack on you. Please try to stay objective.
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Originally Posted by Dean
I'm sorry, I disagree, and Stoptechs own documentation and physics appear to disagree as well. As I understand it, debris and outgassing are mostly a thing of the past with modern pad formulation and manufacturing processes... You clearly have access to people and resources I don't. Given these documents, would it be possible for you to discuss this with the enginerers at Stoptech?
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I will go back and read the whitepapers you posted regarding offset piston sizes as well as follow up with the Stoptech folks. It's possible they didn't feel the need to go into all of the engineering details with a "dumb race car driver." (that's a self description, by the way)
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Originally Posted by Dean
I believe this discussion started as a discussion about brake options to increase feel and minimize fade. And It's good to see that you agree that balance etc. is an issue when not in a maximum braking zone as was my original statement.
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Just to be clear, I meant chassis balance, not brake balance. Brake balance is insignificant when not braking at the maximum.
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Originally Posted by Dean
I said "I appreciate your further description of brake operation, especially the tire dynamics", and I do. Since you don't wish to discuss the intersection of torque curves, transients, etc. I'm not sure there is anything left to discuss on that front.
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I don't know how to interpret that. It may mean that you still believe your pin/hole theory is applicable. Or not. It's not clear to me.
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Originally Posted by Dean
Sorry, my math was in error. I typed 45, not 42.5 into my calculator. 42.5 results in 209.7 x 2 = 419.4 and the Stoptechs comes down to 375. This is 89% the surface area. I don't have the piston circles, but the Stoptechs appear to be 328mm rotors, and stock are approximately 290mm. This is 13% more rotor diameter. So we have 89% the piston area and 113% the diameter. I am still having a hard time understanding how this can shift 10% bias to the rear. Any thoughts?
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I tried for quite some time to figure out what you were doing with your math. I'm still not sure I know what you were trying to calculate.
The pressure exerted on the pad is the brake line pressure multiplied by the surface area of the pistons. Lets assume that brake line pressure and the cf between the pad and rotors are constant for both systems. The area of a circle is pi*r^2. For the stock pistons, that's 3.1415 * 21.25mm^2 = 1,418mm^2. Since there's two pistons, the total piston area is 2,837mm^2. The Stoptech is 3.1415 * (18mm^2 + 20mm^2) = 2,274.5mm^2.
Given the same cf brake pads and the same brake line pressure, that gives the stock system a brake torque constant of 290mm / 2 * 2,837mm^2 = 411,365mm^3. The Stoptech system has a brake torque constant of 328mm / 2 * 2,274.5mm^2 = 373,018mm^3. The difference is (411,365mm^3 - 373,018mm^3) / 373,018mm^3 = 10.28%. The Stoptech system is 10.28% less than the stock system. Unless I screwed up my math somewhere.
Regardless of how this thread was started, I entered into it because I saw several issues with the way you were discussing brake systems (i.e.-wider rotors better than larger diameter rotors, NASCAR as an example to back that up, poor brake design causing lock-up prior to the tires adhesion limits being exceeded, braking and ABS described with a pin and hole analogy, etc.) My only purpose was to help you and the readers of this thread understand how brakes work.
When I read your last post, it seemed you were more interested in showing where I may be inaccurate regarding sidebars rather than digging further into how brakes work. Perhaps I used the wrong word when I said I don't want to talk about theory. What I really meant was I don't want use your theories of extreme analogies to attempt to describe a braking system. I am interested in further discussion of torque curves, etc.
Gary
Sheehan Motor Racing
www.teamSMR.com