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Thread: Not trying to stir the pot
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10-12-2004 #61
qship how are you arguing? you haven't put any information out there?? or really said much at all on this thread. I feel the same way you do, that you won't ever change your mind. I think the crossdrilling being bad thing is an internet trend, and most people are just going along with it.(I do appreciate your input on my rear brakes though Well see ya guys on other posts
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10-12-2004 #62
Best thread ever
38 to go; I wanted in somehow...
10-12-2004 #63Registered User- Join Date
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[QUOTE=dennis68]Pad area very much plays into braking performance, the same way pad composition does. Nice try though, throw the 3rd year engineering major-math out there to confuse the point-almost got me.QUOTE]
Okay.....care to elaborate as to how? Again, not saying wrong or right, but you offered really nothing to substantiate other than "it just does". I'm totally not a braking expert, so I'd like to hear the explanation.
Pad composition most certainly affects mu_k, and also how mu_k will change with temperature. I agree 100% on that point, but you can't just make an arbitrary connection between pad material and pad area.
A quote from another site that I came across purely by accident today (I swear I made my post before I read it):
"Coefficient of friction does not depend on surface area, but rather the friction value, multiplied by the force applied (by the caliper pistons to the pad). Surface area has a lot to do with pad wear, or think of a rotor that has a ¼" swept area. It will still stop the car the same amount, but the pads won't last as long."
Seems to support that derned engineering crap that nobody wants to believe
10-12-2004 #64dennis68 GuestIn a stone cold braking contest I would agree that brake pad size has little to do with stopping distance, however I am not aware of anybody who operates their brakes under those conditions. Since a larger surface area is more capable of disipating heat and heat is the leader in brake fade, it stands to reason that under normal operating conditions brake pad size doea have a substantial impact on stopping distance. Sorry, I don't have a formula to show how this works and I actually don't use them at all for the most part, practical application wins over text book everytime. :icon996:
10-12-2004 #65Registered User- Join Date
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That seems reasonable.
BUT, does this argument directly apply to drilled rotors (which was supposed to be the focus, I think we got slightly off-track)? A thought experiment says that the holes provide no area to create and conduct heat (which is what braking is, Kinetic to thermal conversion), or in other words the contact area has been reduced. At first this seems to suggest that it would act in the same way as a reduced pad area. BUT, I have to wonder what is going on at the unused portion of the pad at any instantaneous second. Also, it is not like the holes are circumferential; they pass through the pad, and are followed by solid material. So how does this affect things? It does not seem entirely unplausible for well placed holes to allow the brake pads to perform as effectively (or at least as far as the a moderately skilled driver can tell) as if they were against a solid rotor.
I tend to lean toward the holes not reducing braking performance nearly as much as physically removing material from the pad. Either that, or I don't have a good mental image of how much "equivalent area" each hole removes. You could do a ratio of areas (solid vs drilled) perhaps, then decrease the pad on the solid rotor by the corresponding percentage? Would that be equivalent?
10-12-2004 #66yup! now i got a nose blead.
It's shake and bake!!! and i helped!
Drewco Homes
10-12-2004 #67Registered User- Join Date
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Oh, and it bugs me when people say things like "practical over theory". Just about everything can be accounted for with an accurate model. I guarantee the pros HAVE theories and equations that precisely explain what we're talking about, it's just we don't know about it. So really all that statement says is we don't know enough yet to account for what we've seen.
the best exception: tires. They're incredibly complicated. But the science is getting better and the mathematical models more accurate every day.
10-12-2004 #68dennis68 GuestYeah Firestone and Goodyear know all about building better tires these days. Yes, I have worked for both and have done my share of tire recalls. My point was that theroy is good to get the mind thinking but you can never plan for practicality on paper. I deal with DCX engineering on this all the time, they design , and it's good until you try and put it to use in a real world enviornment. That when I get to re-design to work correctly.
10-12-2004 #69So Dennis, since you are such a real world type of guy, what kind of real world testing have you done? I know I have been stepping on your feet this whole post, but it seems as if we are representing to differnet sides of an argument or should i say discussion. The only reason why I ask you for testing data is that you are making a point that holes do not work, I am merely questioning that theory. If I was to say They definetly do work, I would have to back up my presumption with hard facts and data which i don't really see here, I mostly see people just getting irritated because I am not going along with their ideas. All I see is bland statements with no real facts to back it up. The only real problem with these engineering discussions is that it seems so easy to argue back and forth and find loop holes in peoples ideas, kinda like Kerry v Bush. One person is always going to think the other way and there is no way to convince them otherwise. Basically this is a good discussion. THere isn't going to be any for sure answer. I just think that people should not state things that they overheard somewhere else, and state them as a fact here, because that is the new trend to go along with. I am not pretending to know much at all here, just exploring a different side to these theorys. Well maybe we can agree that there is no for sure answer. I guess it would be pretty hard to do a real world test to see how they helped in brake fade. I don't think a test like Baers is sufficient, i believe all they did was put the brakes on a fixed machine spin them up fast, apply the brakes and thest the temperature output, I don't think that replicates real life standards, where you have a weight of a vehicle and brakes inside of a wheel next to a hot engine, and the acceleration of a car to stop
10-13-2004 #70