For your first set of points, I didn't write that article. If you read closely, it agrees with the other quotes Maxi found. In fact it had many of the exact same quotes. The authors claim was if your going to buy cross drilled, those were the only ones he would buy and those were the reasons.

I have read the water dispersal thing several times. PCCBs are definitely better because of 1/2 the weight and no fade in street use. Yes, your correct the no fade thing on the steel brakes have nothing to do with cross drilling and should not be part of the discussion.

I looked up the 24 hours racing rules for the Ring and Lemans and there is nothing about brakes. Some claim the carbon brakes are better because of the high temperatures. You can see the rotors glowing at night. No or little fade, ligher unsprung weight and deeper braking into the corners means faster cars.

Why do the high end cars have them? I have repeatedly read bad for the track, fine for the street and will ask around. PCCBs are clearly better but not a direct issue of cross drilling even through the street versions are cross drilled

BTW, the "nav" is not mandatory but actually an option (except on the TT). The screen your referring to is the PCM where all kinds of computer or radio info is displayed. Nav is a module you can buy just as a cell phone BT is a module you can buy using the same screen.

JCW parts are factory warranted. Normal wear parts are not. Pads are rotors are wear items. You can bet they know the normal times for wear, your talking about the maintenaince plan, not the warranty. Yeah, my salesman tried to convince me to get 4 years because the brakes and clutch would go. But if your doing autox, be very aware that can void the warranty, If your dont believe it, just read https://www.northamericanmotoring.co...ad.php?t=49580 Skip's ordeal over the MM act and being denied warranty work partly because of tracking the car. Its very doubtful you will win a MM case because of performance parts. Ive tried to find a single case where a consumer won based on performance parts and cannot.

No, did not feel the JCW brakes did much of anything other than be bling. Silly me had to have a "full JCW car". In the end it was just money thrown away. I did not feel anything different and if you read the discussions on MINI2 about the brakes, you will see the complaints that the are only marginally larger and just slightly bigger pads, Still single piston calipers.

 

I just did a quick search of the relevent PDFs.

You may have read old rule sets but 2007 ACO Le Mans GT2 regulations REQUIRE ferrous brake discs (article 12, section 3, paragrah 2), obviously eliminating any carbon or ceramic items.

IMSA rules (applicable in ALMS, which is important for many teams running at Le Mans) state discs are to be ferrous, but can be ceramic with special approval which must be applied for by the manufacturer.

 

Thanks for the detailed and lively discussion.

One would hope that high priced exotic cars with hefty brakes actually perform as good as they look.

Naturally the tendency would be for non exotic cars to copy that with moderately to well priced brake upgrade kits that resemble those found on the exotics.

You can get the look without the high prices of initial cost or the maintenance. I hate to hear how much replacing the pads and rotors are for a Porsche. I know my crossdrilled MINI sized rotors were cheap and I replaced them without much delay once I found the cracks.

Did I need to replace the rotors due to the cracks? Probably not, but a small crack could become a big crack in a hurry and without much warning and on the track or at a driving event might as well be as safe as possible. If I was only using them for the street I could nurse them along and keep the heat down. I seldom go through brake pads for the four years I've had my MINI.

I agree that for the JCW brakes the pads and rotors are wear items and would likely not be covered under warranty if they wear at a fairly normal rate but it it wore much too quickly or unevenly then that might be different. You'd have to work with your dealership.

Certainly alot has been written. It's hard to be certain what would apply directly for the MINI since we can't put that same technology (porsche brakes) on our cars. There is hype and then there is reality.

There is normal use (street driving) and there is high speed closed track driving.

No brake fade after 25 hard stops? Great stuff, can't say that I've ever done that in my MINI even in lapping sessions. I might have done as much as 14 hard stops (hairpin turn) on a short track less than one mile long during a 15 minute session and I wasn't getting any brake fade that I could detect.

 

 

I like the look of a cross drilled rotor on a car as much as the next person. Very sexy and mean looking. In fact I run them on my race car- to further reduce weight.

On the flip side however I'd certainly not suggest this process to those who are considering much track use. The potential for damage and ultimately failure it too great unless you're willing to accept the wear rate and plan to replace them often.



**As a side note the bounty is up to $400 for anyone who can find proof solid of any form of cast in hole iron rotors. Four years and running and nobody has shown this elusive product.

 

To be clear, the article I referenced above does say most cross drilling is bling but it the author were to buy cross drilled brakes, they would be Porsche and he gives his reasons. They are his opinions ... not mine.

I am going to assume that the first reference from m44 and todds are identical ... TCE offers $400 bounty or close to it. I agree with your question. Very often people just repeat what they heard on the internet w/out definitive proof. Urban legends are rampant. You have an excellent question. Are they truely totally cast or drilled? I have no idea nor have the technical expertise to provide an informed opinion, so I have none on the possibility if it could exist or were economically feasible.

I would imagine that no one would ever collect the $400 because the company's under contract would probably not take a picture for the public domain of a proprietary process. I would also guess the quest to find definitive proof does not mean its not true. I see it no different than finding Coca Cola's secret formula. Just because there may be no pictures of Coke's process for mixing the ingredients does not mean they do not exist.

IMO "cross drilled" is probably bling but Maxis original question is "why on the high performance cars?". I'm still guessing water dispersal and can probably find references in Porsche literature for that as a reason.

 

http://www.gtt.uk.com/brakes.asp'

Calipers

No brake fade after 25 hard stops?

It's more than just "hard stops". It would be take your MINI from 62 kph (60 mph) up to top speed, I assume about 140 MPH accelerating as fast as you can and then stop back to 60 mph as hard as you can ... Repeat 25 times in a row.

 

You mean like these from GTT, pictured on my MINI:

 

Wow, they look so totally oversized.

 

The problem is that Porsche doesn't claim the casting process for their rotors. Coke certainly doesn't argue that has some secret formula, but in Porsche official literature it does not even touch upon cast-in holes. The brake write up I found for the 997 Carrera S mentions the casting process of the calipers and the improved wet weather braking (which I can believe, and I'm actually really interested to actually here some more in depth info about this) due to cross drilling but not the cast-in process that is being discussed. To me, it seems that if Porsche has the opportunity to point out some competitive advantage and doesn't, its very likely that said advantage doesn't actually exist.

Now, back to the water evacuation. I've been looking into this and found only very general statements about it. Is there any in depth analysis I can check into on that? I'm not disputing it, it seems to make sense to me, but I'm just interested to hear the actual physics behind it all. For example, since brakes are rotating, I wonder why slots don't do a similar, if not better job at clearing water. The other question is, if it's all about contact between caliper and disk, similar to a tire and road, if it were possible would a swiss cheese looking tire perform better in the wet then a traditional wet weather tire (which to me seems analogous to slotted rotors). I know, I know, how do you inflate a tire with holes in it? Beats me, I'm just curious.

 

Yes they do. They refer to it as "Formula X". Big stink on May 1, 2006 when somebody offered it for sale to Pepsi.

 

I use slotted tires on my car. They have these grooves that run all the way around the outside...

 

Why should it? If it gives a competitive advantage you might think they may advertise it but why should they let competitors know "how" they get the advantage? I dismiss all forum "opinions" w/out definitive references to back them up as opinions. Here are two non-forum opinion references:

PFYC

"One of the biggest misconceptions with drilled rotors is the Porsche OE rotor. If Porsche can have a drilled rotor why can't I? Actually factory Porsche rotors are not drilled at all, they have their holes cast into the structure of the rotor at the casting stage. The holes then become part of the molecular structure and not an after thought when the rotor is finished."

Upgrading Porsche Brakes

"The stock Porsche 930 rotor has cast-in holes, which are superior to drilled rotors ..."

I have read several references that the holes are not fully cast but finished with a drill.

I don't necessarily agree. For example, If Starbucks makes great coffee, and people buy Starbucks based on reputation or whatever, its under no obligation to explain to the public "how" it makes the best coffee.

Everything I've read on this just says it does. I see nothing as to why other than the water vapor is released quicker. I try to avoid "opinions" on forums without the definitive resource to back it up but I'm finding just a lot of "opinions".

Some non-forum quotes:

European cars

"... wet-weather performance is enhanced by cross-drilled discs, which enable rapid dispersal of the water vapor generated at the initiation of braking"

Porsche

"... cross-drilled discs for optimum braking in the wet. The distinctive drill-hole pattern enables faster response by allowing rapid dispersal of the water vapour generated under braking. All four discs are also internally vented for better heat dispersal."

Time after time, they all say the same thing.

hehe, dunno

 

I think we are getting WAY beyond maxi's intention here which was WHY do the high end cars use cross-drilled brake and the cast-in thing has nothing to do with the original question.

IMO the water dispersal thing is reasonable answer. Using cross drilled under heavy full on racing loads may not be a good thing. Dunno. Why does it do better water dispersal? Dunno.

 

Seems like slotted would be better because the water has somewhere to escape. Since the calipers come in from both sides, a hole is an enclosed space. It has to be large enough to handle take all the water without filling. Also, a slot would sweep the entire surface of a pad, where a hole would sweep only a small line across the pad. That's my theory, and it is mine. I own it...*

The "slots" in a tire don't go through to the interior, and neither would the holes. Imagine a tire that had nothing but circular depressions in it.

As for cast holes vs. drilled holes, the surface created by casting is easy to distinguish from drilled. With sand casting (commonly used for iron or steel parts) the surface would be quite rough. With investment or shell casting it would be smother, but still quite different from drilled.

I assume that the reason for preferring cast holes would be that drilling causes stress in the metal around the hole. So, it seems that they wouldn't want to go in with a drill or reamer to clean out a cast hole. It would tend to defeat the purpose. However, there might be unwanted side-effects from casting holes. The pillars in the mold that will become holes in the cast piece might cause turbulence in the molten metal when it is poured into the mold. This might have an effect on the solidity of the casting. Porosity is one of the major problems with cast parts.

*Monte Python sketch with Mrs. Anne Elk

 

Ahh, I see what you're saying about the tires. And yes, that's exactly what I was thinking about the water with regard to slotted rotors. If that is the case, then it looks like indeed there is no other reason aside from looks for cross drilling.

chows4us, you knock all these "forum opinions" but what are these non-forum sources you point to? Just because they aren't on a message board doesn't boost their credibility. Personally, I trust the folks at TCE more than PFYC, and who is Bill Gregory (excuse me if he's an expert, I simply do not know...)? Let me see, if I post my ideas in an official looking PDF with some great acronyms and my full name, does it make it me more credible?

"Time after time, they all say the same thing."...like every brake expert pointing to no benefits of slotting aside from looking cool. Those two links you provide really don't help in disproving the experts that were quoted at the beginning of this thread. In fact, I'm tempted to say the European Car article simply parroted what Porsche told them through the blurb you link to next.

I don't think the pre-cast partial hole theory is any better than plain cross drilling, however, because like Robin Casady said, the drilling process will weaken the rotors just the same as a regular drilled rotor negating any advantage. Maybe this is actually the truth, though, and the origin of the rumour. It would make sense, wouldn't it? Porsche can't use it as marketing because it has no real advantage over other cross drilled rotors, but its close enough that people may mistake it for fully cast holes.

And finally, I don't think we're getting beyond the original poster's question. I still claim that cross drilling is nothing more than aesthetic, although the water reason makes some sense to me. You disagree. Isn't that his original question? WHY these brakes are on the car? All I've been doing is explaining my position on this and asking you to refine yours.

lhoboy, I'm claiming that Coke does not dispute the EXISTENCE of such a formula. The contents of that mean nothing, just like the existence of cast drilled rotors does not betray the process which is required to manufacture them.

 

I agree on the published literature. If I were a mfg of such part (as is the internet rumor) I'd surely make it known why my parts were to be superior over conventional drilling! That alone contradicts the rumor to no end.

As for which one is better, IF they do exist, the holes are perhaps less prone to cracking due to the lack of tooling placed upon them. That in my opinion doesn't change the constant thermal problems of expansion and contraction they go through when used. That heat cycling alone in (again my personal opinion) the far greater cause of the cracking than how the hole was inserted.

I remain open minded, skpetical to say the least, but open minded.

 

Its also because factory rotors are usually a much harder compound. I've seen OEM rotors with 50-60k miles and look like they have 15-20. Hard to beat 'em.

 

Also non-definitive. I didn't say they were definitive, just some more referenes. I said:

I try to avoid "opinions" on forums without the definitive resource to back it up but I'm finding just a lot of "opinions".

I have found nothing but a bunch of opinions and for both sides. I've read many, many "opinions" that they are in fact cast in, just as much as the people who do not believe. It works both ways.

The reason? Again the most prevalent and the advertised reason seems to be water dispersal.

And lastly, the marketing issue. You can't prove or disprove something where you don't have the answer. Just because you may think it wise to advertise the advantage, others may not. How many more cars do you think Porsche would sell based on this fairly obscure tidbit of knowledge? Is someone who was going to buy a MB AMG whatever going to run down and to their local Porsche dealer if they found out why? IMO, very doubtful. Different marques attract different people for their own reasons. I would think MB shoppers don't cross shop Porsche anymore than Ferrari owners would.

Todd wrote: If I were a mfg of such part (as is the internet rumor) I'd surely make it known why my parts were to be superior over conventional drilling!

That may be true. But thats what your selling. Porsche doesn't sell brakes. It looks like they engineer and design them contracting them to be build by Brembo and SHW (supposedly). Porsche sells cars of which brakes are one component. Does the average Porsche buyer know or even care about the reason? Take a looks at their sales literature, even the thicker 40 - 80 page explanation of a car. At best brakes rate about 2 - 3 lines of info (except for the PCCBs).

As I've said, I can find no definitive soure one way or the other. They do it, they claim its about water dispersal in their advertising literature. I read "opinions" on both sides that they are cast in and some say not. Until Porsche decides to publicize it, I guess we won't know. Internet opnions, on both sides of the argument, are just that, opinions.

 

When has the obscurity of specs stopped a car company from pushing every aspect it could? It doesn't matter how many more cars are sold from that one piece, what matters is the whole package. If you exclude knowledge because it isn't a huge, earth shaking piece of information, then car companies would have little to talk about.

The fact is they could simply add two words "cast-in" to their literature and they have increased saleability to a number of people. Will they buy cars? Maybe yes, maybe no, but it costs them nothing to add that detail. It seems rather irrational to omit something that could increase sales or even just buzz when it costs nothing.

Again, I go back to Porsche's sensible management in its history. They are driven by a bottom line like every car company, and seem to have kept a close eye on it much better than almost any other manufacturer. To omit such a piece of performance information is simply not within character of this company, a company that you pointed out so well strives to overengineer. Now why would they hide this aspect of overengineering?

Aside from this character argument, however, it would be wise to discuss the issue of opinions, ideas, rumours, etc.

There's a lot of talk about opinions. Who knows if this is true or that is true? It's possible that we can't conclusively prove this position one way or another. We can, however, conclusively say that Porsche does not say it has cast in holes. We can conclusively say that the statement that they are cast is just rumour.

But these things prove nothing.

However, we can also conclusively state that experts who have examined Porsche rotors confirm they are not cast with holes, using physical evidence I might add. Others claim differently but provide no physical or direct evidence, and I have yet to see an analysis supporting the cast-in claim that parallels those disputing it.

All the claims about cast-in holes stem from one source pointing to another to another until we don't know where it came from. I do know where TCE's claim from. It came from their first hand experience. This is where I see the problem. Credibility. So we can argue and argue over the crediblity, but I have shown where my points originate from. Now it's just up to the reader to decide what sources they trust the most.

 

Actually, this is awesome. I/we have learnt a lot from reading all of these posts.
Lets debate/discussion continue.

Material may be the key. Put the hi-tech Carbon-Carbon and Carbon Ceremic aside, do you think there might be some different in hi-end oem, lo-end oem and aftermarket drilled/slotted rotors, in term of material that they've used, that make its more/less reliable (cracking problem, etc.).

 

Exactly. I see no facts on either side of the discussion. Until the car company speaks, all discussion is moot. It's speculation ... even if its "expert opinion". Regardless of who makes them, they are not definitive. If, in fact, its true, then I guess the expert opinion is not so expert. However, since we don't know, we don't know what we dont know

 

I think it's been a great discussion. For many years for me. Yet in all these years and speak with folks within the industry (certainly much deeper than small shop!) I found nobody who could substantiate the claim/rumor. So much so that I've become willing to pay to see it. My opions are not a lot more "official" other than having researched it more to date

The carbon and other materials present a whole new set of circumstances for production options. Of which I know nothing..

 

Does anyone have photos of cracks? (you know what i mean)

 

just google "cracked rotors" in images and you will find many