09 ralliart vs 09 wrx
Jul 1, 2009, 09:21 AM
#121
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Evo brakes are better then DSM brakes in every single way, particularly GS-T brakes. You get bigger rotors, bigger calipers with more pistons, and most importantly, bigger pads to act on those rotors. All three cars (Evo, GSX, GS-T) have different sized master cylinders, so it would not be safe to assume the Evo and RA are the same.
Jul 1, 2009, 10:06 AM
#123
The pad and rotor is completely relevant for the coefficient of friction (CoF for now) calculations. A brake pad with 1sq unit of area will obviously have a smaller CoF than a 2sq unit of area pad made out of the same material - assuming that the force applied to the rotor is the same between the two. If size wasn't one of the most important factors (and the calipers ability to apply enough pressure), then there would be no reason for race cars to have HUGE brakes.
Ok - to be fair, *theoretically* you could have a smaller caliper/pad exert as much friction as a larger set, but the requirement for more exotic materials is necessary, or you would have significantly shortened component life.
Ok - to be fair, *theoretically* you could have a smaller caliper/pad exert as much friction as a larger set, but the requirement for more exotic materials is necessary, or you would have significantly shortened component life.
Jul 1, 2009, 10:12 AM
#124
Think of it another way, if the braking force comes from the pressure in the system acting on the pistons, how can increasing the size of the pad increase the force? Does it increase the pressure in the system? Nope, does it increase the size of part that applies that force to the pads? Nope, you're simply spreading the same force over a larger area. The same net force is applied to the rotors. If you wear hockey gloves, can you lift more weight?
Jul 1, 2009, 12:35 PM
#125
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I think Amby is forgetting that the force gets distributed throughout the pad, therefore pad size does matter. However it would reach a point where the pad size is too large and the force distributed wouldn't be enough. But the point is you can't just ignore the fact that the pad makes contact, causing friction and exerting mechanical energy with heat as a by-product.
That's amazing. I expect a thesis and long paper on this breath-taking theory.
Jul 1, 2009, 12:45 PM
#126
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Read the articles rather than simply arguing it. Piston area is what dictates braking force. As I said before, if you increased the pad area but kept the piston area the same, nothing would happen, you'd still be exerting the same force on the rotor. What people are saying is equivalent to arguing that what shoes you wear has an effect on the gravitational force because you're distributing the force over a larger area. That's not correct. The total force is the same regardless.
Jul 1, 2009, 01:01 PM
#127
Just going to quote myself here because it still makes sense. Amby your saying that by applying a larger area of friction to the wheel it WONT make it slow down quicker? So if you holding a plate and try to stop it with your fingertips it will slow down the same as when applying the same pressure with your palms????
That's amazing. I expect a thesis and long paper on this breath-taking theory.
That's amazing. I expect a thesis and long paper on this breath-taking theory.
Jul 1, 2009, 01:05 PM
#128
This came up earlier when someone said that pad area had an effect on braking. No proof was provided, just a theory that flew in the face of provided results and basic physics, which are clearly wrong. The results I posted suggested just that, a BBK has no effect on a single stop. For a sustained beating, they can be very useful but if you want to improve emergency braking, changing the pad material should be sufficient. Alternatively, you can find a way to apply more force to the brakes by somehow increasing the pressure in the system. I see no reason to spend thousands on a BBK when for most people, it's bling. If you want new calipers, I'd look at the Evo Brembos as a cheaper alternative.
Jul 1, 2009, 02:16 PM
#129
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Typically in basic force diagrams the Normal force (N) is equal to the weight of the object (m * g (acceleration due to gravity)). But in the case of brake pads on rotors and the whole system (which is fairly complicated, but the part we are arguing about here is pretty basic). The weight is doing very little (especially since the weight is all countered by the force from retaining clips etc), what the normal force is on the pads is the force from the pistons pushing the pads (which is the force from the foot on the pedal, translated through fluid into a larger force by the master cylinder).
The actual size of the pad does NOT matter. With equal force and equal material a quarter sized pad, and a human body sized pad would not stop a car any faster. Trust me, not only did I get a 4 on all three of my AP physics tests (though heat and E&M don't matter much here) and just finished taking college physics 1 and 2 including the labs (where we experimented with things like the above).
The whole physics of a car's braking system is fairly complicated. But heat and wear are the main reasons for having large pads (and rotors), along with having more room for more pistons to press on them, and more area to have a better likelyhood of consistent coefficient of friction between the rotor and the pad. The larger the pad/rotor the more it can handle disipating heat and the more material there is to wear down.
Just going to quote myself here because it still makes sense. Amby your saying that by applying a larger area of friction to the wheel it WONT make it slow down quicker? So if you holding a plate and try to stop it with your fingertips it will slow down the same as when applying the same pressure with your palms????
That's amazing. I expect a thesis and long paper on this breath-taking theory.
That's amazing. I expect a thesis and long paper on this breath-taking theory.
And assuming the coefficiant of friction is the same for your palms as it is your fingertips you are correct, if you can manage to apply the same amount of force from each.
Jul 1, 2009, 02:33 PM
#130
Hell, if doing well in physics is enough, I have a year of university physics under my belt and my sister has a PhD in space physics. We're not talking about rocket science here, it's fundamental physics and there are plenty of articles in this very thread that explain it clearly.
UT, apparently physics doesn't apply to Evom.
UT, apparently physics doesn't apply to Evom
.
Jul 1, 2009, 02:37 PM
#131
Evolved Member
Physics can not be argued. But in practice there is no quarter sized pad made that can do this, and last anyway, that's why OEMs will choose larger pads when given a choice. So, bottom line is, I really don't see what the argument here is. So yeah, in laboratory conditions, all things being equal where no other outside factors can interefere, a tiny itty bitty pad will work - but in the real world you want bigger pads.
Last edited by GPTourer; Jul 1, 2009 at 02:41 PM.
Jul 1, 2009, 02:43 PM
#132
You don't want quarter sized pads because they'd be overwhelmed by heat very quickly. However, this doesn't mean you need or even want a BBK for the street. That is what's being discussed. Rather than **** away thousands on a BBK that won't help stopping distance, most people would be better served with better brake pads (since I doubt the stockers are that good) and different fluid. Even for weekend racers, that setup is usually sufficient. If you really need a BBK, you don't have to ask and you should be damn knowledgeable on the fundamentals of braking that so many here apparently are not.
Jul 1, 2009, 02:46 PM
#133
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Just stop right there. Nothing else is needed. So whats the point of talking about superman pads made of unobtanium that satisfy a simple physics equation? NOTHING. It doesn't apply to this discussion.
Jul 1, 2009, 02:46 PM
#134
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Hell, if doing well in physics is enough, I have a year of university physics under my belt and my sister has a PhD in space physics. We're not talking about rocket science here, it's fundamental physics and there are plenty of articles in this very thread that explain it clearly.
UT, apparently physics doesn't apply to Evom.
UT, apparently physics doesn't apply to Evom
. Though I doubt they'll be able to understand it.It is very fundamental physics (the pad/rotor system, at least), we're talking like second week of first year highschool physics. First you learn about force in frictionless magic land. Then you add friction.