Please don't buy drilled rotors!!!

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I would not worry about it as I would have no problems running these wrong way rotors.
I was reading up and the difference would be about 100 degrees which isn't much when you consider XP12's can take about 1,850 degrees F.
You have a much lighter car also which makes a big difference

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How (and when) was that temp difference measured?

Personally, if the kit's vendor isn't going to send me the correct rotors for each side, or at least straight vane rotors, I'd want my money back. It is either a cost-cutting measure or a lack of availability driving this and neither yields an acceptable rsult.

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I seriously doubt that the direction of the vanes will make any difference in performance.

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How (and when) was that temp difference measured?

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To be honest I just found some info on an Audi forum
http://www.audizine.com/forum/showthread.php/329948-Directional-Vanes-How-important-are-they

Like I said I understand that it is wrong but yeah I'm not really worried about it. The rotor is still a 13 inch 24lb. heat sink and I'm sure it will perform just fine at the track. If it doesn't, I will certainly post it up on here.

I am grateful Dr. Diff produced a pretty good Stage 4 brake kit for the money, so no way am I returning them. If rotors with the opposite vanes are made I will just buy two more

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Pretty cheap compared to the $20,000 rotors.

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There was all sorts of companies out at SEMA with CF rotors as well...bunch of offshore/probably cheaper sorta ones too.

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My Stage 4 brake kit uses Mercedes rotors because they are the only off-the-shelf part deep enough to keep the fat calipers away from the spokes of a commonly available/reasonably priced wheel.

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I disagree;
I have run the "cheap" drilled rotors for many years on many different cars with no issues.By "cheap" I mean the auto store replacement rotors that some one has drilled in their shop.
Yes I agree the serve no purpose other than look cool, yes less material means less heat disapation, and yes more surface area the greater possibility of crack nuclation.... However on the street these are vary minor inefficiencys. Even in autocross events your brakes donot get hot enough for any of this to make a difference. I have found that the pads wear excessively and the rotors start to develop un-even wear long before any material fatigue can take place..... And that's on a daily driver; so these issues will be even less evident on a "good weather" car.
The quickest I have ever had a set fail was on a modern silverado I drove daily and hauled many cars/parts with. I went thru a set of ebay drilled rotors in 10k miles. Even then I blame the ceramic pads more than I do the rotors.

IMO if you like how the look go for it, if you are trying to build a "race car" you are never going to get there with ebay parts, so stop being cheap.

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Drilled rotors are fine for the street and autocross because you don't build up heat as high when compared to driving a track day at a road course. Driving repeat extended hard laps at a road course will crack any cast iron rotor eventually, drilled or not.

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Are you inferring its the elevated temps that mainly causes the cracking cracking issue? Because I thought that cracking was related more to varying and repeated temp changes, not the ultimate temp, and if that is true, seems like street use would have more and wider temp changes then a closed circuit race track use. I'm not sure of the temp swings.

I would think most would agree a drilled rotor would crack easier then a solid rotor, and most will agreed a failed rotor when being driven/used is kinda bad, where we agree to disagree and reagree is how likely that is to happen and how much risk one is comfortable with assuming that risk.

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Are you inferring its the elevated temps that mainly causes the cracking cracking issue? Because I thought that cracking was related more to varying and repeated temp changes, not the ultimate temp, and if that is true, seems like street use would have more and wider temp changes then a closed circuit race track use. I'm not sure of the temp swings.

I would think most would agree a drilled rotor would crack easier then a solid rotor, and most will agreed a failed rotor when being driven/used is kinda bad, where we agree to disagree and reagree is how likely that is to happen and how much risk one is comfortable with assuming that risk.

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Probably? What the heck do I know?

I drive a 40 year old Plymouth...
I'm not that smart,
haha!

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Holes in pretty much anything are evil stress risers, avoid them.

I know of a set of drilled rotors that didn't even make it 10k miles before cracking. Yeah, they were home drilled about 20 years ago. Don't care, no drilled for me. Those that want them know that I'm laughing at your ignorance.

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Now I'm laughing at your ignorance.

Holes cast into the rotor during manufacturing do not promote stress fractures.
Holes drilled into rotors after casting will lead to fractures.

That's been proven through the years.

The holes provide limited outgassing, reduce weight, and save raw materials. They also look sporty to some people. That's why they get used.

Sometimes performance oriented auto manufacturers investigate things a wee bit more thoroughly than internet keyboard warriors.

















Now, would you like to revise that statement?

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I think we are splitting hairs here, a hole, drilled or cast, is a stress riser compared to no hole, period.

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The king of splitting hairs comments about others splitting hairs?






Obviously, rotors with holes are inferior to non-holed rotors. That's why you'll never see them on supercars costing hundreds of thousands of dollars.




OOPS!! I misspoke. That car cost a couple million dollars, runs 250+ mph, and has zero engineering behind it.
Stupid VW! What were they thinking?

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I think we are splitting hairs here, a hole, drilled or cast, is a stress riser compared to no hole, period.

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I was a wilwood R&D Engineer for 2 years and have been crew in many forms of racing for over 20 years. After wilwood I spent 7 years in R&D with ecomotors.com. Keyboard warrior I am not.

I guess we're both laughing. No known metal rotor has those holes cast into them, even if they are those with cast-in holes they are still stress risers. If nothing else, review "Engineer to Win". That they were drilled as opposed to being formed by some other method is a small part of the total picture. Anything that changes the stress flow path or disrupts it is a stress riser.

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As previously stated, drilled rotors are put on those cars for the buyers, because they think they're cool. Not because they're a better solution. Marketing trumps Engineering & Science every time. So those rotors prove nothing about actual performance. Can you prove that those cars set their high water marks wearing drilled rotors? We all know that they're sold with them, proves nothing. Most real Engineers have a bit better grasp of things than keyboard engineers.

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Surprise! I'm one of the guys who said drilled rotors are used because people think they're cool.

We all know that "real engineers" get their butts kicked by marketing on a regular basis. Keep spouting off with the whole engineer bit. I know a TON of engineers (worldwide) and can tell you some of those guys can't engineer their way out of a wet paper bag.

Frequently, "engineers" get caught up in minutiae. For the engineers out there, that means trivial stuff.
They go and go and go until they can't go anymore. They're measuring carbon content to the angstrom and studying the temperatures at which the base material goes from a plastic state to the liquid state despite the fact that you never want your product to get there.

Yes, all holes in rotors are stress risers.

Can you spot the stress risers in this pic?



If you said the vent holes, fastener holes, and contours around the fastener bosses you'd be partially correct.

How about this one?



See all of those slots? Those create fracture points that can not only move laterally but also across the width of the rotor by originating at the bottom of the cut.

ALL rotors have stress risers. You simply ENGINEER around them. Know that some tool paths will lead to more prevalent points of failure. Cutting will generally lead to an easier failure path than proper forming the features while casting.

You don't have to be a great engineer to know that metals have stress. All you have to do is measure a piece of flat cold rolled steel, cut into one side of it and measure the piece again. You will see deflection in the part due to stress in the steel introduced during rolling.

All formed structures are going to have some sort of stress. That stress is always looking for a way to get out. A good engineer will find the shapes and manufacturing processes that limit the failure rate of the finished product. Once you push that far away from the product's intended use it's time to call it done. In brake rotors you can limit the failure rate but you can't prevent it.

Pull the feather out of your engineer's cap and realize that other people sometimes know what they're talking about.

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I just want to say reading along with this has been SUPER FUN.

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Careful. Fun leads to a higher failure rate.

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Now now guys, keep it serious please.
How about drilled rear drums?

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That may not be too bad of an idea. It will let some of the heat trapped within the drum to leave. Just put it on the drum face. That shouldn't be a critical spot.

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i have done FUN things at times, then afterward wonder if that should have happened..........

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What was her name?

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holes for drum cooling have been around forever. mostly used in the backing plate,

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