Cross drilled rotors
04-02-2003, 11:26 PM
#2
Nordschleife Master
Oh Boy! <img border="0" alt="[hiha]" title="" src="graemlins/roflmao.gif" />
Forget it if you want them to work right and last awhile. Don't go ruin a perfectly good set of rotors.
Forget it if you want them to work right and last awhile. Don't go ruin a perfectly good set of rotors.
04-02-2003, 11:47 PM
#3
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From what I have heard, the drilled rotors crack. The early Porsche rotors were drilled up until the failures surfaced. Now Porsche casts in the holes. No failures.
04-02-2003, 11:49 PM
#4
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So what is the difference between a new set of rotors with no holes and a new set of rotors with holes, besides a $100 a piece. How are cross drilled rotors made.
04-03-2003, 12:12 AM
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When the brakes are applied, the friction and heat causes the brake pads to generate a gas. This gas builds up (like how water builds up under tires) and will reduce the clamping force. This condition is known as "Brake Fade".
What you refer to as "crossed drilled rotors" reflects the old method of drilling rotors to vent the hot gasses. Slotting the rotors is another variation on this theme.
The improved method Porsche uses to create "Vented" rotors is to pour the molten metal into a rotor mold (casting) where by the mold creates the holes. Then the blank rotor face and bearing surfaces are machined.
What you refer to as "crossed drilled rotors" reflects the old method of drilling rotors to vent the hot gasses. Slotting the rotors is another variation on this theme.
The improved method Porsche uses to create "Vented" rotors is to pour the molten metal into a rotor mold (casting) where by the mold creates the holes. Then the blank rotor face and bearing surfaces are machined.
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04-03-2003, 02:18 AM
#8
Race Director
From Porsche's website, "Discs are cross-drilled to enhance braking in the wet. The brakes respond faster because the water vapour pressure that builds up during braking can be released more easily."
Ive read some great threads about drilled/slotted/cast/whatever rotors, if you like tommorow when its not past my bedtime Ill post a link or 2. Basically, Porsche really doesnt come out and say "they stop the car better, they help with this, they do that" anymore. wonder why...
Ive read some great threads about drilled/slotted/cast/whatever rotors, if you like tommorow when its not past my bedtime Ill post a link or 2. Basically, Porsche really doesnt come out and say "they stop the car better, they help with this, they do that" anymore. wonder why...
04-03-2003, 02:23 AM
#9
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">wonder why...
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Lawyers
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Lawyers
04-03-2003, 02:49 AM
#10
Race Director
I think this calls for a revival of the Altima 30-page brake thread...
<a href="http://www.altimas.net/forum/showthread.php?s=58f147a67bd410d18546269f68baf5dd&threadid=32327&perpage =15&pagenumber=1" target="_blank">Altimas.net Pimpy Brakes</a>
Anyone and everyone got in for the ***-whooping!
<a href="http://www.altimas.net/forum/showthread.php?s=58f147a67bd410d18546269f68baf5dd&threadid=32327&perpage =15&pagenumber=1" target="_blank">Altimas.net Pimpy Brakes</a>
Anyone and everyone got in for the ***-whooping!
04-03-2003, 02:54 AM
#11
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Drilliing your own rotors is a bad idea unless you know what your doing. Regular drilling causes problems, via heat and stress. Leading to cracks, and that;s if you get all the holes drilled in the proper place. Drill one set of holes closer than average and your just asking for a crack.
Even profesionally done rotors have a tendency to crack.
For street use get some profesional slotted rotors. For harsh track use get cross drilled and inspect them AFTER EVERY RACE.
I've seen the results of shattered rotors. Granted they stop the car quickly, but it is far from pretty.
Even profesionally done rotors have a tendency to crack.
For street use get some profesional slotted rotors. For harsh track use get cross drilled and inspect them AFTER EVERY RACE.
I've seen the results of shattered rotors. Granted they stop the car quickly, but it is far from pretty.
04-03-2003, 03:43 AM
#12
been there, done that. over 5,000 miles and no problems. key is proper layout, right tools, and relieving the stresses by radiusing the holes. This is the front disc for our 944NA.
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04-03-2003, 09:45 AM
#13
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While I was at the shop last night I went ahead and asked. "You can't turn vented discs." Simple enough. He took a look and told me mine don't need to be anyway. 
Lucky me.
Lucky me.
04-03-2003, 12:01 PM
#14
Drifting
I picked some up from vertex auto last year for my n/a. My old ones were warped so i figured why not spend a little more and get the good stuff. Combined with metal master pads, the braking force is sooooo much better. (Maybe my old ones were crap...). If I remember correctly the drilled OEM rotors were in the 100$ region and the regular are about 60$. These are cast, not drilled though.
Justin
Justin
04-03-2003, 12:58 PM
#15
Race Director
I have been running Zimmerman drilled rotors on the front of my 2460lbs NA 944 Spec car for 24 track days. This inculded 13 944-spec races and 3 other races. 
I also installed custom 3" cooling ducts and have found that the rotors are not cracked or worn to any degree. I have run metal master pads (2 sets) and KFP Magnum Golds (1 set, working on second) on the car.
Of course I cannot say that they make that car stop better. I'd like to think so however..
I also installed custom 3" cooling ducts and have found that the rotors are not cracked or worn to any degree. I have run metal master pads (2 sets) and KFP Magnum Golds (1 set, working on second) on the car.
Of course I cannot say that they make that car stop better. I'd like to think so however..