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Old 05-20-2011, 05:30 PM   #1
M3Monsta
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Cross drilled Rotors?

Just a quick question, what is the difference between normal rotors and cross drilled? (Physical difference) And what are the differences in performance (if there are any)

Also, is there a big price jump?

Thanks.
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Old 05-20-2011, 05:34 PM   #2
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There's blank (standard), drilled and slotted.

Blanks work the best. Period.


Blank:



Drilled:



Slotted:
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Old 05-20-2011, 05:40 PM   #3
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Originally Posted by OrientBlau View Post
There's blank (standard), drilled and slotted.

Blanks work the best. Period.
true, but they look so damn good

blank - best, reason they are stock

slotted - faster cooling, slightly less surface area than blanks

drilled - less surface area than blank's. faster to warm up and faster to cool down. possibility to crack with crazy heat on the track after alot of abuse

and they just look sooo much cooler

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Old 05-21-2011, 01:19 AM   #4
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There's blank (standard), drilled and slotted.

Blanks work the best. Period.
I think a 2-piece floating drilled design (like the 330 performance rotors and the rotors found on newer M-cars) would probably be better than single-piece blanks. The floating design allows for lesser weights and for lower overall brake temperatures. Both factors lead to better brake performance. While a blank floating rotor might be even better, they're not exactly common. I don't think any BMW has come with blank floating rotors since the E39 M5.

I don't think cracks will be a significant concern on a well-designed rotors. You don't really hear about the newer M cars cracking their rotors all the time.
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Old 05-21-2011, 01:56 AM   #5
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I think a 2-piece floating drilled design (like the 330 performance rotors and the rotors found on newer M-cars) would probably be better than single-piece blanks. The floating design allows for lesser weights and for lower overall brake temperatures. Both factors lead to better brake performance. While a blank floating rotor might be even better, they're not exactly common. I don't think any BMW has come with blank floating rotors since the E39 M5.

I don't think cracks will be a significant concern on a well-designed rotors. You don't really hear about the newer M cars cracking their rotors all the time.
Exactly. For all those about OE..well floating cross drilled rotors are factory equipment on the M3 ZCP and CSL. So where's your logic now. Not only as stated will they run cooler from being a floating hat design, weigh less for performance, directionally vented vanes, they also keep the heat away from the bearings compared to solid blanks.

Don't generalize here people. rusted poorly designed and made blanks can be much worse than a fairly good cross drilled(and vice versa). A good perforated floating hat design rotor is much better than a blank.
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Old 05-21-2011, 02:35 AM   #6
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Quote:
Originally Posted by TerraPhantm View Post
I think a 2-piece floating drilled design (like the 330 performance rotors and the rotors found on newer M-cars) would probably be better than single-piece blanks. The floating design allows for lesser weights and for lower overall brake temperatures. Both factors lead to better brake performance. While a blank floating rotor might be even better, they're not exactly common. I don't think any BMW has come with blank floating rotors since the E39 M5.

I don't think cracks will be a significant concern on a well-designed rotors. You don't really hear about the newer M cars cracking their rotors all the time.
I agree with everything you say other than two things:

-Lower overall brake temperatures, no. What does a floating rotor have anything to do with the cooling of the rotor? If anything, overall temperatures might be higher since rotor heat can't travel to the top hat any more.

-Floating rotors are quite common when there is the money and the car ends up on the track. BMW used them stock on the E46 M3 CSL/ZCP and E92 M3. Look at any of the good brake kits for race use and they are almost always floating. Most factory race cars these days come with them from the factory.
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Old 05-21-2011, 05:14 AM   #7
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I agree with everything you say other than two things:

-Lower overall brake temperatures, no. What does a floating rotor have anything to do with the cooling of the rotor? If anything, overall temperatures might be higher since rotor heat can't travel to the top hat any more.

-Floating rotors are quite common when there is the money and the car ends up on the track. BMW used them stock on the E46 M3 CSL/ZCP and E92 M3. Look at any of the good brake kits for race use and they are almost always floating. Most factory race cars these days come with them from the factory.
Well I was thinking lower temperatures for two reasons: A) aluminum is better at dissipating heat than iron. And B) Generally floating rotors also have directional cooling vanes - I don't think I've ever seen a set that didn't have them. I've yet to see a 1-piece rotor with directional vanes sold for the E46

For the second point - read my post more carefully. I said blank floating rotors, like the ones on the euro E36 M3 and euro E39 M5, aren't too common these days. The drilled ones like the ones found on the euro e46 m3, CSL/ZCP, and all recent M-cars are obviously fairly common.
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Old 05-21-2011, 12:39 PM   #8
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Well I was thinking lower temperatures for two reasons: A) aluminum is better at dissipating heat than iron. And B) Generally floating rotors also have directional cooling vanes - I don't think I've ever seen a set that didn't have them. I've yet to see a 1-piece rotor with directional vanes sold for the E46

For the second point - read my post more carefully. I said blank floating rotors, like the ones on the euro E36 M3 and euro E39 M5, aren't too common these days. The drilled ones like the ones found on the euro e46 m3, CSL/ZCP, and all recent M-cars are obviously fairly common.
Well, that separation and small contact area between the floating rotor surface and center hat brings heat transfer way down to negligible levels. The directional cooling vanes aren't a floating rotor specific thing either.

And yes, I did misread the "blank" floating rotor part. In response, I will post a picture of Performance Friction's really cool floating and dimpled rotors that they use on the Formula 1 C63 safety cars. Directionally vented, dimples with a nice radius, a special mounting setup that puts the top at bolts in double shear, and then there is the fact that they are like huge 15" rotors.

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Old 05-20-2011, 05:36 PM   #9
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Originally Posted by M3Monsta View Post
what is the difference between normal rotors and cross drilled? (Physical difference)
One has holes drilled through them, one is a solid piece of steel.

Quote:
Originally Posted by M3Monsta View Post
what are the differences in performance (if there are any)
From what I've seen, braking distance isn't decreased but the rotor can run cooler as it has more vents than the standard vented rotor.

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Originally Posted by M3Monsta View Post
Also, is there a big price jump?
Yes and no. Depends on brand, model, etc.
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Old 05-20-2011, 05:43 PM   #10
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So you say that I should get normal oem rotor over oem performance rotor ?
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Old 05-20-2011, 05:45 PM   #11
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^those are cast perforated rotors if I'm not mistaken. They don't have the weakness of cross drilled ones by design.
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Old 05-20-2011, 05:47 PM   #12
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the OEM performance ones are cast perforated?
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Old 05-20-2011, 05:49 PM   #13
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the OEM performance ones are cast perforated?
I was replying to your message with the picture of the Brembo kit. No idea about OEM perf ones
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Old 05-20-2011, 05:51 PM   #14
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I was replying to your message with the picture of the Brembo kit. No idea about OEM perf ones
That picture was for drool references only.
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Old 05-20-2011, 05:52 PM   #15
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Agreed. Drilled does look much better.
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Old 05-20-2011, 05:54 PM   #16
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Zimmermann products seems to be cast perforated (even if vendors advertise them as cross-drilled... marketing...)
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Old 05-20-2011, 06:04 PM   #17
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Slotted or not slotted are best. The cross drilled rotors have been known to crack between the holes and eventually grenade regardless of brand. I've seen Dba rotors go boom.
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Old 05-20-2011, 06:34 PM   #18
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Well im not planning on going to the track, just a couple street races here and there.

The drilled looks NICE though.
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Old 05-20-2011, 07:06 PM   #19
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drilled, the best performer, never going back no cracks
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Old 05-20-2011, 07:13 PM   #20
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drilled, the best performer, never going back no cracks
Drilled is NOT the best performer.
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