I made a counter agrument, and then offered 3 sources, one with all nice scientific calculations done out for you to support my argument.
I wouldn't put a whole lot of trust into those numbers/calculations just look over those again and you should see what I mean. anyway weren't you the one who said you can't trust others you need to figure them out for yourself. I'm gonna spend some time if I got it looking at his theories (or facts) again but the way it was presented just didn't seem right.
About the 20% cooler thing, I'm not really sure how much the 3.9% effects it, because I'm not sure how much faster the air would cool something like that. Guess its back to the drawing board.
As you can probably tell I really don't know which are mathmatically better yet, and I might never cause I am lazy
Originally posted by MaddMatt kdlang: I'm a God huh? Let's see, I made a counter agrument, and then offered 3 sources, one with all nice scientific calculations done out for you to support my argument. I am some God. Wow. I impress myself.
Your right, prolly not god, how about bitch, fag, ass, pussy, cock sucker, homo....U know those well. And I don't care either way about braking distance or all the other crap, I'm cool with my stock brakes, I just hate you. jus kidding, I got luv 4 all. Put up a link 2 your guy's site so U can take the Discussion over there, or buy an Altima.
Originally posted by tooler If anyone who is still reading this thread is interested in learning about how to efficiently modify a car in general, please see my post at http://www.altimas.net/forum/showthr...hreadid=33262.
It is not a continuation of this discussion.
It's just some advice on how to make your own informed decisions in the future without needing 30 pages of a forum thread.
this is just a thought so please dont flame me for it. is it possible that the Brembos that alex installed were larger than the OEM ones that they replaced? i think that would account for the increaced stopping ability.
PS. white GSR, i am a 3rd year HS student
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it may be P-fuzzy if ya nasty, but its pfuzzy00 if ya on AIM
i dont think most people understand the importance of this discussion...
why do u think people outside of the altima community have decided to join this discussion? contrary to some beliefs here... we're are not here to simply bad mouth a single individual (alex).. we're here to set a few things straight. there are a lot of universalities in this discussion that go behind the scope of this forum.
#1. Vendors/Manufacturers have been making unproven, and often misleading claims to their products in order to sell them better... and the often under-educated consumer believes them.
Alex has been caught in the act of doing it in the beginning of this thread.. we're just here to make sure it is pointed out.. so hopefully it wont happen again in the future. All posts on the internet are public.. so be careful with your claims.. as you may never know who's reading them.
#2. We are talking about the design of crossed drilled/rotors versus oem style blank rotors. This discussion applies to everyone who owns a car, wishes to modify their brakes, AND cares about performance. (I put the "AND" there since I realized a lot of folks on this board care more for looks than anything else)
Please don't try and discredit anyone from the discussion by saying "you don't have an Altima.. so you don't know what you're saying.".. unless the altima has a special braking system design exclusive to altimas.
#3. Physic is universal. It doesn't matter where you are.. you can be on the moon.. and the same laws of physics will apply. You can change the application or the subject... the same laws of physics still apply.
Besides that.. I just want to bring up the point that alex continues to claim that he is only relaying information from the manufacturer and has no responsibility beyond that. well.. if you were selling a prepackaged item and regurgitating the pamphlet... fine. Maybe you, as with most consumers, are just misinformed too. Although it may seem immoral.. who am I to say.
But lets not forget an important point here, you, or your shop is actually modifying the product (cross drilling blank brembo rotors), marketing that modification as a performance upgrade, then selling them (i'm assuming here) at a higher price for profit... and that my friend.. just seems wrong to me.
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Quote:
Originally posted by RyanDB2
I haven't seen any actual pysics other than hypotheticals not backed up by formulas, here I will get you started with the easiest one first
<btw before I get started just to let everyone know I am very tired so if anything seems wrong point it out to me>
First, good job. Thinking in detail about things, instead of heeding marketing propaganda, is a good thing. You're performing a "back of the envelope" calculation, in which you make some reasonable assumptions about the sizes of things, and what effects are important. This is a powerful technique, especially with practice.
Unfortunately, there are some problems... but they can be addressed with the powerful technique of "dimensional analysis." In other words, keeping careful track of your units. IMHO, if undergrads in physics courses would learn one skill, this should be it.
Quote:
Surface area of a cylinder= 2 pi r^2 + pi*R^2*H
The 2 pi r^2 is simply the formula for surface area of a cicle multiplied by two for the top and bottom.
The second part is the surface area of the unfolded (i.e. rectangular) wall of the cylinder.
The second term is wrong, as can be seen with dimensional analysis. The first term, 2*pi*r^2, has dimensions of length squared (as "2" and "pi" do not have units, and "r" has units of length). This is an area, which is what you want.
The second term, pi*r^2*h, has dimensions of length cubed (as "r" and "h" have units of length), which is a volume. You want an area. In fact, pi*r^2*h is the volume of the cylinder. You want the circumference of the circle (not its area) times the height... this gives the area of the unfolded rectangle you described. The circumference is 2*pi*r, so in total, the surface area of a cylinder is:
A = 2*pi*r^2 + 2*pi*r*h
Now, when you drill a hole in something, you lose
the surface area from the circular "endcaps" but gain the surface area from the cylinder walls. So the change in surface area from drilling is:
delta_A = 2*pi*r*h - 2*pi*r^2
You can see that if r=h, there is no change in surface area; if r > h, you lose surface area; and if r < h, you gain surface area.
Please note that for the typical vented rotor, which has two thin disks with mostly-empty space in between, you look at each disk individually,
and "h" has to be fairly small.
So, to maximize surface area, you would drill a very large number of small-radius holes. However, I can imagine that the airflow over the hole walls would be quite poor in that case, which would tend to offset the larger surface area.
Quote:
Surface area of holes= 2*3.14*12.7^2+3.14*12.7^2*6.35= 1861.205955mm
Back to dimensional analysis, and the power thereof: When you write down a number that has units (such as the radius of a rotor), always write the units with it. Then, when you do the math (multiplications and additions), do it to the units as well. You want an area as your answer, which would be "mm^2", but you wrote "mm." When I've been a teaching assistant, that was always a sure sign that people were faking their units.
So, you should have said:
2*3.14*(12.7 mm)^2 + 3.14*(12.7 mm)^2*(6.35 mm)
= 1013 mm^2 + 3216 mm^3
Now, you can't add unlike units, so you'd see that there was an error in your formulas (plus, I got a different number from you, but that's another story). Doing math on the units "for real" is like checking to make sure the oil isn't spilling on the ground after an oil change... it's pretty easy, and catches some really bad mistakes!
Originally posted by peachfuzz this is just a thought so please dont flame me for it. is it possible that the Brembos that alex installed were larger than the OEM ones that they replaced? i think that would account for the increaced stopping ability.
Well if you wade through this entire frikin thread, the answers are to be found an pages 1, 2, 4, 7, 12, and probably 10 or 11 other pages .
Here is the short answer as I understand it:
If your brakes currently have the ability to lock-em-up, then your stopping distance will not change one iota by increasing the size of the disk. If you are skidding the tires, the brakes are no longer in the equation - the tires are the limiting factor. If they are locked up, it doesn't matter if you have a 7" Yugo rotor, or a 14" 6 piston Brembo setup.
However, when you increase the size of the rotors, you now have a braking sytem which can a) absorb more heat into the rotor due to more thermal mass, and b) dissipate that heat into the atmosphere quicker due to more surface area. Bottom line? - you can take your car down from 100 mph to 20 mph more times per lap before you melt your rotors or fade your brakes, than if you had smaller rotors - hence one of the main reasons that racers use bigger brakes.
(boring Mustang stuff here -----> Using the g-tech meter, I measured stoping distance with my original brakes (you know, those embaracing little frisby sized front rotors that came on my stock 98GT) at 120 ft, +/- a few feet (ABS fully engaged). Guess what the stoping distance was after I installed the 4 piston, 13" Brembo system? You guessed it, 120 ft, +/- a few feet. And yes, I am aware of the fact that the g-tech is not the most precise instrument in the world, yet it is likely that it is a few orders of magnitude more accurate than Alex's butt-o-meter )
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Damn!
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