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Old 05-20-2003, 08:18 PM   #76
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OK, here's my final point in passing:

Rates of reaction (such as heating or cooling) are governed by several factors:
1)Temperature (temp. difference in the case of heat transfer)
2)Surface area
3)Catalyst (not applicable for most physical reactions such as heating)

The cross drilled rotor has more surface area to work with and the same temperature difference, therefore being able to transfer heat away quicker, staving away heat transfer moreso than slotted or solid rotors.

And the powerslot site says 85-93%. And that counts the entire area of the rotor, not just the swept part (which is all that matters when dealing with a contact patch).


And you can call me on trying to sound smart all you want. These are irrefutable points.
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Old 05-20-2003, 09:06 PM   #77
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And BTW, even though yeah some people have studied more than me, everything I've talked about here I've studied myself. I haven't gotten myself over my head in the Physics or thermo.
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Old 05-20-2003, 09:51 PM   #78
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I thinnk your confusing cross drilled with vented.

In a vented disc (and all modern discs should be vented) there are air vents manufactored into the disc between the two sides/faces, from the our side edge towards the hub. This gives a disc more surface area to improve its ablity to disapaite heat.
If you look at a disc edge on the vents are visable between the two faces.

A Cross drilled disc has holes drilled into each face of the disc, either right through, or into the vents in the middle. This does nothing to increase surface area to aid cooling, since as you open up surface area on the side of the holes, you are also removing an equivilant amount material from the face of the disc. The idea behind is to allow gas build up from the pads somewhere to go in order to prevent brake fade, but comes at the cost of surface area for the pads to work on, and so less braking force. It also weakens the structure of the disc, and so is banned from many forms of Motorsport, and discouraged in others.


With modern pad compounds, and the use of slotted discs there is absolutly no need to cross drill discs in order to remove gas build up, and if the pad manufactors claims are true then is no need to even use slotted discs.




One final note, could we stop the name calling and insuations about the intelligence levels of others.
If someone dosnt understand something dont call them names or accuse of them being stupid.
Instead try to re-explain your point of view in an differnt and easier to understand way, and provide more evidence to surport your view.

In the end if your right and you know thier wrong, but they refuse to accept it, then its their problem, if they want to be ignorant then let them.
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Old 05-21-2003, 12:23 AM   #79
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911GT2,

You must be looking at it differently than us?

Did you read that link that SilverY2KCivic posted?
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Old 05-21-2003, 02:03 AM   #80
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Quote:
Originally posted by 911GT2
OK, here's my final point in passing:...

The cross drilled rotor has more surface area to work with and the same temperature difference, therefore being able to transfer heat away quicker, staving away heat transfer moreso than slotted or solid rotors.

And you can call me on trying to sound smart all you want. These are irrefutable points.
LMAO! There's NOTHING irrefutable about that statement. It's just flat out incorrect. I mean if a rotor has HOLES and dozens of them drilled out of it, how on earth is it going to have MORE surface area (not just the same amount) as a solid faced rotor? I'm sorry, but that's pure ignornace right there especially for one that has studied this. Like mentioned above, I believe maybe you are refering to or thinking of VENTED rotors, rather then X-drilled. Also, any physics oriented person should know, MORE surface area = more area to shed off heat thus allowing better heat dissapation (thermodynamics ). The holes don't help in cooling, not now-a-days anymore at least. They were just there originally back in the day to like slots, help shed off gasses accumulated from the brake pad. I URGE you once again to read that aritcle in the link I posted, the truth of the matter lies within it. I'll believe a person that's designed brake systems for 32 years (and not only for cars either in this guy's case) over a 19 kid that studied physics and certainly isn't reading what others are saying. I suggest you read that article if you haven't done so already. Then go back and re-read this thread to see if maybe, because I'm hoping you just misunderstood what we were talking about, rather than trying to flame with inaccurate information.
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Old 05-21-2003, 05:40 AM   #81
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Quote:
I already argued this stuff with SkylineUSA himself in this thread, then I researched and realized.
See, if this old dog can be taught, a 19 year old kid, should be able to as well. One would think.
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Old 05-21-2003, 07:11 PM   #82
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Cross-drilling does increase surface area. Think about it. And before posting immediately that it doesn't, think about it more.
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Old 05-21-2003, 08:50 PM   #83
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Quote:
Originally posted by 911GT2
Cross-drilling does increase surface area. Think about it. And before posting immediately that it doesn't, think about it more.


Try explianing how, and prehaps you will realise that it dosn't.


The only way it could would be if the disc was several inchs thick, and solid.
And although Iv seen 2inch wide discs (on Ferraris, Porcsh's Lotus, etc) they were all vented, hence the amount of material drilled through was not a lot, and so the amount of material exposed in the side of the hole, was not enough of an increase to compensate for the amount of material removed from each surface (and in the case of vented discs, theres 4 surfaces to remove material from, as four faces are drilled through). Both out side faces exposed to the pads, and both inside faces exposed by the vents.
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Old 05-21-2003, 09:32 PM   #84
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Quote:
Originally posted by 911GT2
Cross-drilling does increase surface area. Think about it. And before posting immediately that it doesn't, think about it more.
hmm...

Ok thought about it, and guess what, you're still incorrect!

Yup, thought about it some more and you're still wrong! Maybe you should go ask your physics professor why your statement is not correct, ok?
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Old 05-21-2003, 09:36 PM   #85
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Quote:
Originally posted by 911GT2
Cross-drilling does increase surface area. Think about it. And before posting immediately that it doesn't, think about it more.
And also, we keep showing and PROVING to you why your wrong on that statement, yet you can't even shown us proof why you believe it so strongly to be true? Are you exempt from proof and automatically right? Sorry man, but that's not how it works. I'll bet you haven't even read that link I posted up about brake rotors.
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Old 05-22-2003, 12:18 AM   #86
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I thought about it , and yep the same conclution as Silver and Moppie. The kid is wrong.

I would hate to be wrong, when I post information. I personaly take it as a challenge to prove my point, with facts. Kid you have none. Just your opinion, and we all know about opinions.

We know you have no proof, because you do not know what you are talking about, point blank.

Let see, you have a flat surface, then you put holes in it, taking some of the surface area away, seems like less surface area to me. I thought about again.

Kid you need to change classes, because physics is just not your cup of tea. Or prove us wrong, which you cannot.
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Old 05-22-2003, 01:13 AM   #87
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Hmm, maybe I shoulda majored in thermodynamics. LOL!

On a totally unrelated note (well related to the topic of brakes), I was looking back at the posts in this thread and wondering how much you're Apex rotors set you back $$$ wise? Althought I haven't yet experienced ANY fade what-so-ever from my Power Slots, they do tend to het up my wheels nice and toasty after a decent mountain pass run if I run it hard enough. I'm still going to get a full brake fluid flush soon here and replaced with some Motul RBF600 DOT4 race fluid and all lines replaced with Goodridge S/S lines. So once that's done maybe I'll notice a temp difference, I know I'll notice a pedal feel difference, as it takes a tiny bit more effort on the pedal than it used to, to enguage them. Is the heating of the wheels (the fronts where the discs are) kinda caused by the mass that the slots take away?
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Old 05-22-2003, 02:27 AM   #88
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I think you'll find that your old brake set up would have been transfering just as much heat into the wheel as your new one, its just that since you have the new brake set up you know notice it.

If you really want to know if its made a differnce then put the old brakes on and make the same run, and see if you feel any differnce.
Ultimatly you need to do this at a race track where you can record your lap times.


Heat transfer from the brakes into the rest of the hub assembly is of serious concern.
In race cars it can over heat wheel bearings, and if wheel nuts are over tightened cause wheel studs to break as it all expands with the heat.
This is why you always see wheel nuts being tightened with a torque wrench, to ensure they are all even, and not to tight.
They should also be checked at the end of every race, or stage in a rally, as they constant heating and cooling can work them lose.
(and remember that a lot of heat is also comeing back into the wheel off the tyre, chances are if it was just warm to the touch, then the heat came off the tyre, or the wheel bearings, and not the brakes)
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Old 05-22-2003, 02:38 AM   #89
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Maybe it's a mix of both tyre heat and rotor heat, Moppie? =\ But you're right, I never checked my brakes as much when I had the stock ones on, well actually a few times I did, and it seems it was cooler with the stock OE rotors, but maybe I wasn't puching my car as much to the limit either. Could it also have anything to do with the pads I'm using? AEM/Nissin high performance OE spec pads. What I should do is get some active ducting to feed cool air to my front rotors.
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Old 05-22-2003, 05:12 PM   #90
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Well obviously it depends on the thickness of the rotor to make the surface area. Here, I'll explain what I mean:

Area (let's just do the area of one cross-drilled hole ok?

NON CROSS DRILLED

Area=2(pi)(radius)^2 (the 2 is for each side of the rotor)

CROSS DRILLED

Area=2(pi)(R)(l) (the l is the thickness of the rotor)

Now, to find out where the areas equal each other, let's make the two areas equal:

2(pi)(radius)^2=2(pi)(R)(l)

Cancel out the repeating terms and you come up with r=l

So as long as the rotor is thicker than the radius of the hole, you end up with ultimately more surface area. And note that that radius of the holes is usually very small and while the rotors aren't always really thick, they're thicker 90% of the time, especially considering that cross-drilled brakes are usually aftermarket and therefore thicker.

There, I've explained myself.
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