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Old 05-22-2003, 05:48 PM   #91
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That forumla is way off.

Where do account for the area being removed by the drilling process, for the cross drilled rotors?

The way I read the formula also, is its just for area. Or am I missing something, please correct me if I am wrong.
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Old 05-22-2003, 06:00 PM   #92
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Quote:
Originally posted by SkylineUSA
That forumla is way off.

Where do account for the area being removed by the drilling process, for the cross drilled rotors?

The way I read the formula also, is its just for area. Or am I missing something, please correct me if I am wrong.
For the cross drilled equation, note that I only included the rectangle formed by the circumference of the hole (2*pi*radius) multiplied by the rotor's thickness.

And like I said before, the rate of reaction (heat transfer in this case) is dictated by 3 things:

1)Surface area (the more surface area, the quicker something happens). Prove this by putting a drop of water on your counter. Then, put a drop on the other side, but make is cover more area (i.e. spread it out). Which dries first??

2)Temperature (temp. difference in the case of heat transfer). Cross drilling, slotted or solid rotors don't really make much difference in my argument.

3)Catalyst - not applicable.
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Old 05-22-2003, 06:01 PM   #93
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And I proved myself, don't disprove it by saying "that's way off". Do it out for yourself on a piece of paper.
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Old 05-23-2003, 12:21 AM   #94
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While your maths is right, it is as you said only right for a very thick rotor, and very small holes.
I have never seen a cross drilled rotor where the size of the hole was such that the area removed was less than the amount of surface area created. The holes have to be either so small that they become useless as air or trapped gas is unable to flow though them efficantly, or the disc is so think it has to be vented, and so amount of material expose or the side of the hole opened up is still not significantly greater than the amount removed.


Remember that your removing material from both sides of the disc, and unless I read it wrong you failed to account for that in your equations, this would be the flaw I think SkylineUSA is looking for.


There is another problem, its no good opening up surface area if its not exposed to a moving air flow which will have a cooling effect.
Remember the holes are drilled to allow gas from the brake pads somewhere to escape to. This gas is super heated, and remains trapped in the holes for considerable amount of the discs rotation. This clearly prevents the surface area exposed on the inside of the holes from working to help cool the disc, so altough you might increase the amount of surface area in a very thick disc, with very small holes, you have actualy reduced the amount of surface area that is able to be cooled.


And of course you have removed material that would be in contact with the pads, which defeats the whole purpose of a brake disc, and so you still need to increase the size to compensate, which of course increases the ablity of the disc to handle heat build up.
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Old 05-23-2003, 05:45 PM   #95
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I get what you're saying and I'm not really asking you to agree with me.

And my example only took into account the surface area of one hole. Over one hole, the surface area grows so long as the conditions are met. If one hole creates more surface area, multiple holes over multiple discs, well, I figured you guys could get that one on your own

And when you think about it, you don't really require tiny holes or overly thick rotors. The radius of one cross-drilled hole is tiny anyways, the rotor needs not be very thick to meet my stated conditions.

And you can compensate for the loss in swept area by increasing the force, like many cross-drilled braking systems do (I'm thinking along the lines of the Brembo Big Red Brakes system). They just add more pistons and more braking force capability.
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Old 05-23-2003, 08:45 PM   #96
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More pistons in a caliper doesn't nessacerily mean it's better. 4 is adaquate enuogh, but 6 or 8 is just rediculous. Generally (like with engines when comparing 8, 10 and 12 cylinder motors) the more you have, the smaller they need to be to even fit in the caliper, so the 4 pot Brembos that Porsche uses is about all the braking force anyone would need in a street car.
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Old 05-23-2003, 09:10 PM   #97
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Quote:
Originally posted by 911GT2

And you can compensate for the loss in swept area by increasing the force, like many cross-drilled braking systems do (I'm thinking along the lines of the Brembo Big Red Brakes system). They just add more pistons and more braking force capability.

Larger calipers wont do much to increase the force applied to the pad, they just allow you to use a bigger pad to cover more of the disc.
But then this has its own problems. More pad on disc means more friction which means more heat. It may stop really well once, but then may suffer from extreme fade, to the point that you actualy end up with worse brakes then if you had stuck with the smaller caliper.



Basicly what were saying here is cross drilling your Dics will have little to no effect on over all braking performance, and may infact lessen it, or make the disc dangerously prone to fracturing.
If you are having problems with brake fade then start by upgrading your pads.
If you still want better brakes then up grade to a larger disc with the appriate sized caliper and master cylinder, and if you still want better brakes, or you are getting into some regular and serious circut racing consider upgrading to race spec pads, and possibly some slotted rotors if you dont believe the pad manufactors claim about no more fade.
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Old 05-24-2003, 02:59 PM   #98
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Quote:
Originally posted by SilverY2KCivic
More pistons in a caliper doesn't nessacerily mean it's better. 4 is adaquate enuogh, but 6 or 8 is just rediculous. Generally (like with engines when comparing 8, 10 and 12 cylinder motors) the more you have, the smaller they need to be to even fit in the caliper, so the 4 pot Brembos that Porsche uses is about all the braking force anyone would need in a street car.
I agree for a street car anything more than 2 per caliper is usually useless. 4 is good for a sportscar, anything more is relegated to racecars and sometimes the luxury sport sedans (IIRC the Audi RS 6 uses 6-pots).

But more than one or two allows for more even braking force and the possibility of more braking force.
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Old 05-24-2003, 03:14 PM   #99
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And one little tidbit I thought I'd share: I'm not asking you guys to agree with me. I've shown my points and that's all I really have to say, I just think that cross drilling certainly doesn't decrease performance. Like moppie said, it may not increase (dramatically or whatsoever) braking performance, but you guys seem to speak of it like it's the antichrist.

If it's as useless as all of you say, it wouldn't be used so much. It may not be useful in all respects, but it's certainly better than solid rotors.
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Old 05-24-2003, 05:48 PM   #100
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Quote:
Originally posted by 911GT2
And one little tidbit I thought I'd share: I'm not asking you guys to agree with me. I've shown my points and that's all I really have to say, I just think that cross drilling certainly doesn't decrease performance. Like moppie said, it may not increase (dramatically or whatsoever) braking performance, but you guys seem to speak of it like it's the antichrist.

If it's as useless as all of you say, it wouldn't be used so much. It may not be useful in all respects, but it's certainly better than solid rotors.
That's the thing, if it's MORE prone (at least twice as prone) to warp or crack than solid rotors, it's not better. Braking force/performance aside, I'd rather have a reliable rotor (solid) that may not brake as well, then an X-drilled that'll mose certainly crack way prematurely with the kind of driving I do. You will not see x-drilled on professional race cars, and it has nothing to do with bans on them, it's all the principle of the matter which is those kind of rotors (x-drilled) on severe duty cars is dangerous. And the cars they ARE used on, again I assure you as will almost anyone else on here, that x-drilled rotors on Ferraris, Porsches and the like are sadly for looks, and nothing performance wise.
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Old 05-25-2003, 12:17 AM   #101
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That's the thing: I don't believe they're only for looks.

Porsche or Ferrari wouldn't use them for looks. Look at their history: they've never done something solely for looks.

And while most cross drilled rotors do tend to crack easily, most don't so long as they're drilled properly (i.e. chamfered). Straight drills cause pressure points which crack easily, chamfered spreads the load.

What I'm basically trying to get across is that they're better over a period of hard braking, but they definitely won't decrease your braking distance.
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Old 05-25-2003, 12:19 AM   #102
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And more prone I agree with, but for something as drastic as twice as prone, you're gonna have to provide some sort of statistics. You know everyone here (even skylineUSA I'd hope) would have a healthy amount of skepticism no matter what side you're arguing for.
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Old 05-25-2003, 02:13 AM   #103
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Quote:
Originally posted by 911GT2
Look at their history: they've never done something solely for looks.

Ummm

One of the reasons many people buy a car like a Ferrari or a Porsche is because of it how it looks.
Its no good building a fast car if it either dosnt look fast, or have a design that is ground breaking and differnt.
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Old 05-25-2003, 02:21 AM   #104
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Quote:
Originally posted by Moppie



Ummm

One of the reasons many people buy a car like a Ferrari or a Porsche is because of it how it looks.
Its no good building a fast car if it either dosnt look fast, or have a design that is ground breaking and differnt.
Just because the owners tend to be stupid, image-obsessed fucks doesn't mean the cars are image-based.

And while I agree, it shouldn't be that way eh?
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Old 05-25-2003, 03:34 AM   #105
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Quote:
Originally posted by 911GT2


Just because the owners tend to be stupid, image-obsessed fucks doesn't mean the cars are image-based.
Well the cars half to be, otherwise not enough ppl would buy them.


Quote:
Originally posted by 911GT2

And while I agree, it shouldn't be that way eh?
No, its way OT, but I think a car can have form as well as function.
IMO its what makes cars like Lotus, Ferrari etc so great. They are the ultimate in both Form and Function.
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