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Suspension & Braking
Have some questions about suspension or brake setups for your E46 BMW? Get all your answers here!

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Old 03-25-2007, 11:36 PM   #61
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I know of some good rotors that i have on my car... check em out.... they are 10 star rotors that seem to keep customers happy, and they guarantee no cracking......http://cgi.ebay.com/ebaymotors/ws/eB...9265728&rd=1,1
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Old 03-26-2007, 08:03 AM   #62
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I know of some good rotors that i have on my car... check em out.... they are 10 star rotors that seem to keep customers happy, and they guarantee no cracking......http://cgi.ebay.com/ebaymotors/ws/eB...9265728&rd=1,1
Personally, I'd be skeptical until I could find out who the actual manufacturer is (it's not MimoUSA).

Also, don't believe the "no cracking" claim. The thing is ALL drilled rotors crack. On good ones, they develop small hairline surface cracking around the holes, but they never join or get to the disc edge before the rotor is worn out. On the not-so-good ones, the cracks join from one hole to the next, and/or run out to the disc edge, then if continued to be used, fail and break apart. But they all crack.
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Old 03-26-2007, 09:18 AM   #63
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Actually, the best deal in quality replacement OE-size rotors right now is from UUC... our Gen2 black-plated rotors are cast to our specifications in North America, and are offered as "packages" with pads, lines, and sensors at reduced cost.

Our regular pricing beats "group buy" pricing.

Details:

http://www.uucmotorwerks.com/rotors

- Rob
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Old 03-26-2007, 09:24 AM   #64
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The way I see it, if nothing else I figure the burden of proof is upon the claim that a particular (or any) rotor is cast with perforations in the disc face. So far all the available evidence shows that they are drilled. While you can't truly prove a negative, the scientific method says that the best theory is that all perforated rotors are drilled until somebody can provide a documented example of one that isn't.
To add to this discussion, which is spilling over from other threads, it is possible to cast-perforate rotors. It's not a myth, but it is the latest internet "bandwagon" to say it can't be done. Yes, many brands are simply machine-drilled, but that's not the point.

We can do cast-perforating with our foundry, but choose not to for practicality and cost reasons. It would end up that we would have to charge the same as BMW Motorsport perforated/floating rotors, about $450/pair, and that's infeasible for non-M service replacement parts.

- Rob
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Old 03-26-2007, 09:31 AM   #65
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good info in this thread.

so, you won't have to worry about cracking in slotted rotors, right? and there are no disadvantages to slotted rotors?
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Old 03-26-2007, 10:45 AM   #66
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To add to this discussion, which is spilling over from other threads, it is possible to cast-perforate rotors. It's not a myth, but it is the latest internet "bandwagon" to say it can't be done. Yes, many brands are simply machine-drilled, but that's not the point.

We can do cast-perforating with our foundry, but choose not to for practicality and cost reasons. It would end up that we would have to charge the same as BMW Motorsport perforated/floating rotors, about $450/pair, and that's infeasible for non-M service replacement parts.

- Rob
So to summarize, your assertion is that it can be done, but nobody does it?

The only reason the distinction matters is due to the internet "bandwagon" that says drilled rotors are bad, but this particular rotor is okay because the holes are cast not drilled, so you should buy it. But if in fact nobody makes a cast rotor and they are all drilled, then that is not a valid basis on which to select a rotor.

As for the assertion that are all perforated rotors are drilled, not cast, if it is a myth as you say, it should be take very little effort to debunk it. All somebody needs to do is provide a picture of a rough casting with holes or a picture of a mold or a patent or some other sort of evidence. If somebody is actually making a cast perforated rotor and it offers a genuine technical advantage, you would expect them to market it as such. At a bare minimum, you would expect them to admit its existence - if they are making cast perforated rotors why in the world would they describe them as drilled?

Last edited by jpr; 03-26-2007 at 10:55 AM. Reason: grammar
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Old 03-26-2007, 12:07 PM   #67
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So to summarize, your assertion is that it can be done, but nobody does it?
That's not what I said at all.

1) It can be done. Fact.

2) Your list of aftermarket brands that are drilled is accurate.

3) OE-manufacturer perforated rotors are made with different methods and standards than aftermarket drilled.

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The only reason the distinction matters is due to the internet "bandwagon" that says drilled rotors are bad, but this particular rotor is okay because the holes are cast not drilled, so you should buy it. But if in fact nobody makes a cast rotor and they are all drilled, then that is not a valid basis on which to select a rotor.
Yes, but none of the aftermarket brands you list are advertised as cast-perforated, are they?

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As for the assertion that are all perforated rotors are drilled, not cast, if it is a myth as you say, it should be take very little effort to debunk it. All somebody needs to do is provide a picture of a rough casting with holes or a picture of a mold or a patent or some other sort of evidence.
There's a good reason you don't see it... vented rotor casting technology is often quite complicated, and if not patented (as some methods are), then is at least a closely protected manufacturing technique. Think about it... you're casting a relatively large piece of iron with multiple channels, and it has to be done in a fairly precise and balanced way. If company A has a better method than company B, they're not going to post pics on an internet message board.

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If somebody is actually making a cast perforated rotor and it offers a genuine technical advantage, you would expect them to market it as such. At a bare minimum, you would expect them to admit its existence - if they are making cast perforated rotors why in the world would they describe them as drilled?
The OE-level manufacturers in question make several lines/grades of product. OE-level, A, B, C - tier stuff depending on the price point of the market. They're not going to say "Our OE stuff is made better than the service replacement stuff" as that shoots their marketing in the foot for the high-volume and higher-profit replacement parts. That's just common business sense.

Additionally, the OE manufacturers do not list the product as drilled, always as "perforated". And, as you and I discussed in another thread, a single instance of a marketing brochure saying "drilled" does not obviate the hundreds of other technical brochure listings as "perforated". Not to mention, the secondary "interference layer" of translation from German to English.

- Rob
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Old 03-26-2007, 12:18 PM   #68
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Okay - name one OE or other manufacturer that makes rotors with cast in holes.
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Old 03-26-2007, 12:31 PM   #69
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Okay - name one OE or other manufacturer that makes rotors with cast in holes.
Why are you asking questions that you know we've discussed in multiple other threads and in phone conversation?

- Rob
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Old 03-26-2007, 12:40 PM   #70
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Why are you asking questions that you know we've discussed in multiple other threads and in phone conversation?

- Rob
You must be thinking of a different jpr - I don't believe I ever spoken with you on the phone nor discussed this subject in any other thread with you.

As for why I keep bringing it up, just chalk me up as the curious sort. If it's done, it should be able to be proved. I've searched and searched and keep coming up with nothing. So please point me in right direction and name even one manufacturer, OE or otherwise, that is claiming to make cast perforated rotors or one of the hundred of other technical brochures that claim it.

Or just comp me one of your BBK's (with drilled rotors of course) and I'll shut up.
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Old 03-26-2007, 01:03 PM   #71
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You must be thinking of a different jpr - I don't believe I ever spoken with you on the phone nor discussed this subject in any other thread with you.
Sorry, meant private e-mail.

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As for why I keep bringing it up, just chalk me up as the curious sort.
Yes, but don't let your curiosity overwhelm simple logic. It's an easy step from "curiosity" to "agenda".

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If it's done, it should be able to be proved.
Nope. See what I said above about proprietary info / intellectual property / manufacturing secrets.

I've established to myself that it can be done. The methods required, however, are not something that our fabrication facility will allow to be publicly discussed.

Let me give you another parallel for intellectual property... "I've heard that BMW uses very sophisticated programming in their DME. Why won't they let me see the code?"

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Or just comp me one of your BBK's (with drilled rotors of course) and I'll shut up.


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Old 03-26-2007, 01:29 PM   #72
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Let me give you another parallel for intellectual property... "I've heard that BMW uses very sophisticated programming in their DME. Why won't they let me see the code?"
But here's the important difference - BMW admits that (1) they have a DME (2) they program it, and (3) that is controls certain things. The intellectual property is in the details of the programming, not its existence. Same thing for a cast perforated rotor. If it existed, you expect to see a claim like "By using our secret proprietary process to cast the holes in to the rotor, our rotors are technically superior for these reasons..." It doesn't tell you how they do it, merely that it is done and it offers enough technical advantages to justify whatever additional expense is incurred.
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Yes, but don't let your curiosity overwhelm simple logic. It's an easy step from "curiosity" to "agenda".
But my curiousity is rooted in simple logic. Various pundits talk about rotors being made with cast in holes, yet there is no evidence to be found of any manufacturer actually doing so. Nor is there any reference in any technical literature on casting or automotive braking. There's not even any claim by any manufacturer of doing so. Considering how little it would take to substaniate the claim of cast in holes, it is significant that it apparently can't be done. In the end, it's really the simplest of logic that says there is no such thing as a cast-perforated rotor - Occam's Razor.

Agenda? It was to get a free BBK, but I guess that's off the table
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Old 03-26-2007, 01:42 PM   #73
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The circular logic is inapplicable.

Have you seen the casting apparatus for a BMW composite manifold? No, and you're not likely to.

Here's a better parallel for you: years ago, there was a technical piece published about the special materials and methods used to make it. It is no longer available, yet clearly it is done.

I think you missed my previous point about why a manufacturer might not want to discuss certain aspects of some product for reasons of negatively impacting their other products... especially as the "premium" product they make is privately-labelled for the vehicle manufacturer.

- Rob

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Old 03-26-2007, 02:03 PM   #74
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Have you seen the casting apparatus for a BMW composite manifold? No, and you're not likely to.

Here's a better parallel for you: years ago, there was a technical piece published about the special materials and methods used to make it. It is no longer available, yet clearly it is done.
It's clearly done and it's existence is often cited even if the details of the method are not disclosed. For example -
Lots of engine pictures here - http://www.worldcarfans.com/photos.c...ngine-in-depth
Paper on intake manifold casting here - http://www.kspg-ag.de/pdfdoc/kspg_pr...anifolds_e.pdf
"Magnesium/aluminum composite construction" in the N52 cited here - http://www.bmwboard.com/articles/view.asp?linkid=428
Long article on the N52 here - http://www.worldcarfans.com/news.cfm/newsID/2040718.001/page/1/lang/eng/country/gcf/bmw/bmw's-new-six-cylinder-engines-in-depth
SME paper "Composite Manifold for BMW V8 Engine Wins Award" here http://www.sme.org/cgi-bin/get-press...21634&TE&&SME&

Bottom line - if it exists, it can be found (and quickly too, I might add)
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Old 03-26-2007, 02:21 PM   #75
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Good work jpr. Thanks for posting.

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Old 03-26-2007, 02:24 PM   #76
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Bottom line - if it exists, it can be found (and quickly too, I might add)
Nonsense.

As I posted, I proved to myself that it can be done - but that doesn't mean I have to prove it to you.

- Rob
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Old 03-26-2007, 02:42 PM   #77
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Nonsense.

As I posted, I proved to myself that it can be done - but that doesn't mean I have to prove it to you.

- Rob
In that case I have rotors with cast in holes I'd like to sell you, honest...

Any interest in bridge? It's not that far from you...
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Old 03-26-2007, 03:36 PM   #78
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In that case I have rotors with cast in holes I'd like to sell you, honest...

Any interest in bridge? It's not that far from you...
Proof positive that "internet homework" is far from the whole story.

- Rob
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Old 03-26-2007, 03:44 PM   #79
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Proof positive that "internet homework" is far from the whole story.

- Rob
But there isn't any proof - that's exactly how the whole thing started.

Let's put in another way - I want to buy a rotor with cast in holes. Who do I call and how do I know what I'm getting?
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Old 03-26-2007, 03:53 PM   #80
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But there isn't any proof - that's exactly how the whole thing started.
There is proof. I have it. I can't share it because it is internal manufacturing intellectual property and not for public dissemination.

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Let's put in another way - I want to buy a rotor with cast in holes. Who do I call and how do I know what I'm getting?
It will cost you $200K. That's what I'll need to cover setup fees and for you to buy an entire production run for the part numbers (left and right), because the "regular" price would be infeasibly high for other purchasers. But, since I don't see the point in wasting time, I'm not actually going to produce them.

Awaiting your next post. If you really want the last word, go right ahead. I promise I've said all I have to say on the subject.

- Rob
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