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Cory M's Avatar
 
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Are rotor holes really cast or drilled?

There is a two page discussion on another board with a $200 prize for anyone who can prove that the OEM Porsche rotor holes are actually cast, and not drilled. It been about 10 months and so far no one has won the money. I know it CAN be done, because I'm an engineer with a company that uses extremely complex castings that include angled holes as small as 0.030" diameter. But I can't prove that any of the rotors made by Brembo or others actually use this process. Is it a myth? Marketing drivel? Are the holes really cast, can you PROVE it?

Here is the challenge and a link to the discussion:

http://corner-carvers.com/forums/showthread.php?t=21273&highlight=cast+holes

Pass the word to other forums;

We have talked about it here a number of time.....
It's on every forum.....
It has the makings of a classic internet rumor.....
There has been talk of one manufacture......
Even one pretty good comment on another forum....

But yet today this still remains; an unsubstantiated rumor. Fueled by fans, believers and 'experts'. Or at least ones who know one, down the block, in the basement, with the lights out....

What is it?

Porsche rotors with CAST in holes.


It has been talked about here with no proof. It has been spoken of in quiet circles. Talk, talk, talk. And at the last Porsche event I worked with the new Boxster....well, they were drilled. Sorry.

Best comment was that the holes were 'cast as pilots' which became dimples as the guy kept trying to dig himself out. Another pointed out that even a pilot woud be foolish if you were drilling or reaming on a CNC as the variation could snap the bit...but he seemed firm. Right up to the point where it came to supplying a pic. His pic of a FINISHED rotor, clearly machined proved nothing.

Want the $200?
Pics of the rough casting, light passing through the hole or a mold pic in the foundry. No questions asked.

Anyone?


*Can't do it but know someone who can?
Send them here: www.tce************************ -right to the bottom of 'late braking news'.

Old 10-17-2005, 12:53 PM
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I've already read a number of threads on it, and none of them (that I have seen) has actually proven that the holes are cast, but everyone assumes that they are and repeats it over and over again. The cracked rotor thread on PP today mentioned it and prompted me to post this. If you have evidence that the holes are cast, then you should contact the guy and collect the $200, let me know how it goes.
Old 10-17-2005, 01:05 PM
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Porsche rotors with CAST in holes?
Old 10-17-2005, 01:06 PM
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I missed that thread. But it basically proves what the guy on CC is saying, the holes are drilled not cast.
Old 10-17-2005, 01:23 PM
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They're drilled.


From Brembo's site:

"Gran Turismo Brake Systems

The Gran Turismo system’s level of technology and performance is unrivaled by any other product on the market. Each system is designed vehicle specific for maximum performance and “Optimum Brake Balance”. Gran Turismo Systems are comprised of lightweight 4, 6 or 8 piston calipers and 1 piece or 2 piece “floating” vented rotors up to 15” in diameter. Calipers are available in red, silver or black and discs are available in cross drilled or slotted. Increased brake torque and thermal capacity, dramatically improves the vehicles performance. This potent combination offers the extreme in Brembo’s leading edge technology for high performance street and track use applications.

Brembo brake systems are fully compatible with your vehicles ABS and traction control systems. Systems are pre-assembled and include all necessary hardware for ease of installation.

Sport Brake Systems

At the Sport level, an end user can find both an introductory performance solution combined with an appealing aesthetic application. The Sport level is comprised of a 1-piece drilled or slotted and solid or vented rotors according to your original manufacturers requirements. A complete set of performance pads may be available.


Where's my $200?
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Old 10-17-2005, 01:26 PM
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I did find you can get cast hole rotors for a neon: http://www.neoncars.com/brakes.htm
Old 10-17-2005, 01:30 PM
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IF it was me paying, I'd be sure the German words were translated correctly before sending you your $200.

Did amyone bother to contact Brembo directly?

Another angle would be for someone to try & collect using the ceramic rotors - they are more likely to be cast.
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Old 10-17-2005, 01:32 PM
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Quote: Did amyone bother to contact Brembo directly?

Actually, according to a Brembo engineer, they never made O.E. rotors for Porsche....only calipers.
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Old 10-17-2005, 01:42 PM
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Don't know if this will help but I was looking closely at the 993 TT rear rotors I have and noticed that a few of the rotor holes were not drilled or cast all the way through. Let me know if pics are warrented.
Old 10-17-2005, 02:12 PM
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Quote:
Originally posted by Donsacto
Don't know if this will help but I was looking closely at the 993 TT rear rotors I have and noticed that a few of the rotor holes were not drilled or cast all the way through. Let me know if pics are warrented.
This may support the idea that dimples are cast in and drilled through afterwards.
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Old 10-17-2005, 02:15 PM
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Quote:
Originally posted by Cory M
I missed that thread. But it basically proves what the guy on CC is saying, the holes are drilled not cast.
Did you even bother to read the thread?

Here is a close up of an oem 993RS rear, the casting roughness is clearly seen below the machined chamfer



The manufacturers stamp, I will have to look up whose this is


BeepBeeps photo only shows Zimmerman drilling a rotor not a Porsche 930 or 993 rotor, the only 2 911 derived models to use cast in holes oem.

Here is a Zimmerman from the rear of a 930, again the casting roughness can be seeen below the chamfer machining


There are 2 tiers of rotors form most of the manufacturers oem through the dealer channel is generally a better quality piece because of tighter tolerances ands specs.

There are no 911 or CArrera rotors w/ cast in holes, only the 964 turbos have cast in holes, all 993 have cast in holes.
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Old 10-17-2005, 02:21 PM
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Quote:
Originally posted by Donsacto
Don't know if this will help but I was looking closely at the 993 TT rear rotors I have and noticed that a few of the rotor holes were not drilled or cast all the way through. Let me know if pics are warrented.
That's because the casting process is imperfect, the casting shells often break, shift and crack causing irregularities which will need a touch up.
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Old 10-17-2005, 02:24 PM
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Quote:
Originally posted by Bill Verburg

The manufacturers stamp, I will have to look up whose this is
The Brembo guy I talked to mentioned a company by the name of SHM, out of Germany. I tried to get a bit more info but it sounded like he didn't want to be bothered.
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Old 10-17-2005, 02:28 PM
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There are 4 or 5 rotor sources in Germany Zimmerman & ATE are 2 of the biggest and best known
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Old 10-17-2005, 02:34 PM
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Have you ever heard of SHM? I came up dry with Google.
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Old 10-17-2005, 02:36 PM
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Yeah Bill, I read the thread. You posted pictures of the cores and the tooling to make the cores, you also showed a close up of the vent. No one is disputing the fact that the vents are cast in, and the cores that you showed do not have the geometry needed to cast holes. A core that would allow for the hoes would have "nubs" (for lack of a better term) on it that the metal would flow around to create the holes. I can't really tell much from the above picture of the 993 disc, but if you've got the proof you should go collect the money. I'm not on a mission to prove the holes aren't cast, I just think that it's interesting how it is simply accepted so universally that the holes are cast, yet it is so difficult for anyone to prove it.

It's ironic that when we cast holes into parts at my job it is generally done to reduce cost, not because it is believed that the metalurgy of the cast hole is superior. Basically if we can cast the holes in it saves us from laser drilling or EDM later on. We do it because it makes the parts cheaper, not because they are any better.

Old 10-17-2005, 02:53 PM
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