I hate to interject a little tech into this thread, but I guess I'll try.
Somebody brought up the point that "Porsche uses crossdrilled rotors, so they must be better, right?" Or something to that effect. There are a few reasons that Porsche rotors are the exception to the rule:
1) The holes are cast in giving a dense boundary layer-type crystalline grain structure around the hole at the microscopic level as opposed to drilling which cuts holes in the existing grain pattern leaving open endgrains, etc, just begging for cracks.
2) The holes are only half the diameter of the holes in most drilled rotors. This reduces the stress concentration factor due to hole interaction which is a function (not linear) of hole diameters and the distance between them.
3) Since the holes are only 1/2 as big they remove only 1/4 as much surface area and mass from the rotor faces as a larger hole. This does a couple of things:
It increases effective pad area compared with larger holes. The larger the pad area the cooler they will run, all else being equal. If the same amount of heat is generated over a larger surface area it will result in a lower temperature for both surfaces.
It increases the mass the rotor faces have to absorb heat with. If the same amount of heat is put into a rotor with a larger mass, it will result in a lower temperature.
3) The holes are placed along the vanes, actually cutting into them giving the vane a "half moon" cut along its width. You can see that here:
This does a couple of things:
First, it greatly increases the surface area of the vanes which allows the entire rotors to run cooler which helps prevent cracks by itself.
Second, it effectively stops cracking on that side of the hole which makes it very difficult to get "hole to hole" cracks that go all the way through the face rotor (you'll get tiny surface "spider cracks" on any rotor, blank included if you look hard enough).
5) The biggest reasons Porsche brakes are so good:
Pad area. Here's a caliper and pad from a Ferrari F355 compared with the Porsche Big Red (painted to look like the Ferrari):
BTW, the last time I saw a car at a PCA event with cracked rotors...it was a Ferrari. They use standard Brembo rotors drilled "the easy way."
Movit sells alot of brakes to Ferrari owners. That's probably one of the reasons why Porsche Monoblock calipers are on backorder worldwide right now damnit!!!
That's why Porsche rotors are the only "crossdrilled" rotors I would ever consider putting on my car...in fact, I'm planning on it.
BTW, many of the above features are not present in older Porsche brakes. The above is for "Big Reds" and newer. I'm not sure what vintage the pic of the cracked Porsche rotors was but they weren't Big Reds.
So, NissanLunatic, how many of these features do your rotors have? Even just one? Didn't think so.
The Jesse guy you talked to at Brembo was an idiot. They never fail? Hang out at the racetrack long enough and you'll see every type of rotor ever made (including Porsche) begin to crack or and need replacement.
The question is was it the rotor's first day at the track, second day, or 10th day?
You people are some of the most idiotic critics I've seen. Go and re-read the posts and it will tell you where I got my info. Go. Don't waste your precious time.
Second, that's not a question, that's a request, and that too, indeed, has been adressed.
20 pages Lunatic. In 20 pages of this thread, you have not once backed your statement of increased stopping power with cross drilled rotors.
I don't mind you selling products. I don't even mind you using this board to promote your business. I even bet the products you sell are pretty darn good quality. I don't even mind that your website is all busted. Half the companies I hit on the net have busted websites. No biggie. You know what? Crossdrilled rotors stop a car just dandy on the street. Absolutely, I wholeheartedly agree 100%. I'll even go out on a limb as say you're likely a swell guy to know personally.
The only thing I mind, in this entire 20 page soap-opera Alex, is you making performance claims that you cannot back up.
One of three things, Alex:
-Show me the data.
-Ship me the rotors and I'll get the data (remember I have a 97 Altima sitting in my driveway).
- STFU about x-drilled rotors having increased braking power.
Actually I lied. The other thing that I mind is you being to pig-headed to open you mind to learn a few things.
edit: changed the number 19 to 20 (that's how many pages there were when I STARTED writing this response.)
20 pages Lunatic. In 20 pages of this thread, you have not once backed your statement of increased stopping power with cross drilled rotors.
I don't mind you selling products. I don't even mind you using this board to promote your business. I even bet the products you sell are pretty darn good quality. I don't even mind that your website is all busted. Half the companies I hit on the net have busted websites. No biggie. You know what? Crossdrilled rotors stop a car just dandy on the street. Absolutely, I wholeheartedly agree 100%. I'll even go out on a limb as say you're likely a swell guy to know personally.
The only thing I mind, in this entire 20 page soap-opera Alex, is you making performance claims that you cannot back up.
One of three things, Alex:
-Show me the data.
-Ship me the rotors and I'll get the data (remember I have a 97 Altima sitting in my driveway).
- STFU about x-drilled rotors having increased braking power.
Actually I lied. The other thing that I mind is you being to pig-headed to open you mind to learn a few things.
edit: changed the number 19 to 20 (that's how many pages there were when I STARTED writing this response.)
I know its hard for you to comprehend simple gestures, so let's not get too complex. You and your four friends HAVE GOT TO READ what's posted. Its getting tiring posting same information over and over
Because owning an older car, and maintaining it, is always cheaper than buying a brand new car. My dad drives his 300K mile car to work every day (he's a master tech) while keeping his nice new car around to run errands and use on the weekends so he can save money on insurance, wear and tear, resale value of his new car - probably so he can have more money for home projects, family, his horses, and whatnot.
Statements like that make you look immature, and really, like you're the loser.
Ryan
Quote:
Originally posted by osama hahahhahahahahhaa, why would someone drive a car for 300k+ miles, hahahahahhaha, loser!!!
I hate to interject a little tech into this thread, but I guess I'll try.
Why start now
Quote:
1) The holes are cast in giving a dense boundary layer-type crystalline grain structure around the hole at the microscopic level as opposed to drilling which cuts holes in the existing grain pattern leaving open endgrains, etc, just begging for cracks.
2) The holes are only half the diameter of the holes in most drilled rotors. This reduces the stress concentration factor due to hole interaction which is a function (not linear) of hole diameters and the distance between them.
Would you believe I just understood every word you typed? I guess that Materials Science degree paid off...
Sounds to me like Porsche has done their homework, as expected. They have taken care of the main reason rotors crack:
Quote:
1) Without teaching the class and booring everyone, just trust me here: Cracks love to form and propogate from sharp edges. When you drill one hole in a vented rotor, you are creating 4 sharp edges. Casting holes in the rotors like Porsche does help. Chamfering the holes you drill helps, although you can't do the 2 sharp edges on the INside of the rotors. Heat treating, cryo cooling it all helps, but doesn't eliminate it. Especially when you factor in my 2nd point.
But, still, if you have a hole in the rotor, my 2nd point will eventually get it.
Quote:
2) Inconsistent cooling: As simply as I can put it, the metal in the rotor IMMEDIATELY surrounding the hole cools at a faster rate than the metal not immediately surrounding the hole. This is a temperature gradient. Temp gradients lead to stress. Remember what I said about how a metal relieves stress? Cracking...at sharp edges...that you created by drilling into the rotor.
Although certainly with the holes cast the sharp edges should not be there. But still, roughly half the Porsches I see on track with the stock cross-drilled rotors are showing faint hairline cracks originating from the holes.
The pic I posted earlier was a 959 awaiting US emmision certification. Not sure if they used this casting method then, or even if they were the original rotors.
Quote:
You and your four friends HAVE GOT TO READ what's posted
Alex, is this appearing in German on your screen or something?
One. More. Time. Alex.
In 20 pages of this thread, you have not once backed your statement of increased stopping power with cross drilled rotors.
Quote:
Its getting tiring posting same information over and over
Tell you what Chuckles, humor me and post it again (the empiracal test data that proves x-drilled has increased stopping power). I missed it somewhere.
Originally posted by Jon A I hate to interject a little tech into this thread, but I guess I'll try.
Somebody brought up the point that "Porsche uses crossdrilled rotors, so they must be better, right?" Or something to that effect. There are a few reasons that Porsche rotors are the exception to the rule:
1) The holes are cast in giving a dense boundary layer-type crystalline grain structure around the hole at the microscopic level as opposed to drilling which cuts holes in the existing grain pattern leaving open endgrains, etc, just begging for cracks.
2) The holes are only half the diameter of the holes in most drilled rotors. This reduces the stress concentration factor due to hole interaction which is a function (not linear) of hole diameters and the distance between them.
3) Since the holes are only 1/2 as big they remove only 1/4 as much surface area and mass from the rotor faces as a larger hole. This does a couple of things:
It increases effective pad area compared with larger holes. The larger the pad area the cooler they will run, all else being equal. If the same amount of heat is generated over a larger surface area it will result in a lower temperature for both surfaces.
It increases the mass the rotor faces have to absorb heat with. If the same amount of heat is put into a rotor with a larger mass, it will result in a lower temperature.
3) The holes are placed along the vanes, actually cutting into them giving the vane a "half moon" cut along its width. You can see that here:
This does a couple of things:
First, it greatly increases the surface area of the vanes which allows the entire rotors to run cooler which helps prevent cracks by itself.
Second, it effectively stops cracking on that side of the hole which makes it very difficult to get "hole to hole" cracks that go all the way through the face rotor (you'll get tiny surface "spider cracks" on any rotor, blank included if you look hard enough).
5) The biggest reasons Porsche brakes are so good:
Pad area. Here's a caliper and pad from a Ferrari F355 compared with the Porsche Big Red (painted to look like the Ferrari):
BTW, the last time I saw a car at a PCA event with cracked rotors...it was a Ferrari. They use standard Brembo rotors drilled "the easy way."
Movit sells alot of brakes to Ferrari owners. That's probably one of the reasons why Porsche Monoblock calipers are on backorder worldwide right now damnit!!!
That's why Porsche rotors are the only "crossdrilled" rotors I would ever consider putting on my car...in fact, I'm planning on it.
BTW, many of the above features are not present in older Porsche brakes. The above is for "Big Reds" and newer. I'm not sure what vintage the pic of the cracked Porsche rotors was but they weren't Big Reds.
So, NissanLunatic, how many of these features do your rotors have? Even just one? Didn't think so.
The Jesse guy you talked to at Brembo was an idiot. They never fail? Hang out at the racetrack long enough and you'll see every type of rotor ever made (including Porsche) begin to crack or and need replacement.
The question is was it the rotor's first day at the track, second day, or 10th day?
I was really impressed by your knowledge, until you turned goofy on me at the end..Do you own a set of Brembo crossdrilled/slotted rotors on your car?
Man, 20 pages! This is entertaining if nothing else. I've been reading all this and watching quietly but since things are starting to go around in circles I thought I'd throw in my thoughts. The technical information that has been presented here has been top notch. There has been a lot of smack talking to go with it, but who cares? As someone said way earlier in the post, thick skin can do wonders. I know there are a lot of people who are lurking on this thread so for their benefit the conclusions drawn here should be made clear. Don't let the fact that there's a lot of trash talking make you miss the truth that is contained here. Let's try and make this as simple as possible so everyone can play along:
Open question to anyone -
Does slotting and cross drilling rotors yield a reduction in stopping distances?
If you think the answer is yes, please explain your response to the best of your ability. Don't say you think so because you read it somewhere, explain it in a technical sense. No one has yet provided any type of response to Cobra's original technical breakdown of the subject that disproves or even contends his points.
Alex, you're getting dogpiled here so you're getting defensive which is understandable, but I think there's some things that need pointing out. Of course your car would feel much better with new Brembo rotors and a pad change. This isn't because the crossdrilling and slotting has any effect, it's simply because they are new parts. I'll also say that they may last longer than the stock parts because they could be of a higher quality than the OEM castings. The problem that's being contended here that they will provide absolutely zero improvement in stopping distance for all the technical reasons put forth previously. To claim otherwise is simply false, and misleads your customers. The car felt better to you because it had a full brake job done compared to old worn out parts. If you had done the same job but used fresh factory parts it would have felt the same.
Sell as many of those brembo rotors as you can, but if people ask you if they make their car stop better as an honest vendor you should say no. Tell them they may last longer than stock hardware, but that the stopping distance will be the same. You should also tell them that if they use these rotors in a severe fashion, they are more likely to crack than non-slotted/drilled rotors because of the inherent effects of the modifications done to them.
To the lurkers - there's a lot of smack talk flying around here and that may piss some of you off. Whether you like these guys or not, you shouldn't ignore what they say because of their delivery method. They're simply trying to ensure that you are an educated consumer and are aware of what you are and aren't getting for your dollars. That's a good thing if you ask me.
Back to being just another face in the crowd.......
I know its hard for you to comprehend simple gestures, so let's not get too complex. You and your four friends HAVE GOT TO READ what's posted. Its getting tiring posting same information over and over
Oh you mean these?
Quote:
a)They rock
b)They look awesome
c)NO SQUEALING, NONE, NONE, WHATSOEVER NO SQUEALING
d)Did I tell you they look awesome
e)Increased stopping power
Oh, well we stand corrected then. Look at this wealth of information! HE EVEN USED AND ORDERED LIST A... B... C...! OMG, It was all a big misunderstanding Alex, now that we know that "they rock," we'd gladly like to give you a shitload of money for your wonderful products.
So, your guys' point is crossdrilled and slotted rotors crack?
Might be Cobras point of contention, but not mine. I know most of your customers will never use them to the extreme like a drivers school or anything like that. So the chance of failure (if done properly like you say) is less. I feel like I've said that before.
I made my point elsewhere: you making dangerous, innaccurate, and unsubstantiated performance claims about a part you sell.
The fact that it took 20 pages to do this says a lot more about you than it does me.
Dimples: Glad you are enjoying the technical discussion. If you have learned something somewhere in this 20 pages of lunacy about how a braking system works and what factors affect how your car stops, then I'm happy. I hope there are many more just like you lurking in the shadows.
Glad you liked that, Matt. Yes, Porsche did their homework.
Good point about inconsistent cooling. Of course you know that the cracks form in the first place frome cyclical loading (fatigue cracks) due to the internal stresses caused by different temperatures in different areas of the rotor (outside faces being hot expand more than the insides of the faces, etc).
The Porsche rotors will tend to be cooler right around the holes like any other drilled rotor--problem. What I think helps that is the rotor overall, stays at a lower temperature not only because of the way the holes are done but because the cooling vanes inside are so well designed overall. As you know, if you keep the rotors cool, they are going to last. Even a cheaply done crossdrilled rotor might last for a very long time if the driver never uses the brakes remotely hard (easy street driving).
Why have I chosen them over Brembo blanks? I do think they will last longer. Due to the above and the fact that the caliper uses a larger pad (it's also lighter and stiffer) and the rotor is thicker...all for the same price. And I can pick up replacement stuff at the local Porsche dealer in a pinch. Sound reasonable?
NissanLunatic,
Do I need to own a Geo Metro and a Corvette Z06 to know which one will be faster around the track? Do I need to own a 747, put lousy parts on it, fly it around for awhile to see if it will fall out of the sky before I know if a part is good enough or not? There's a reason people study Engineering.
Be sure to ask Jesse why Brembo vendors that know their stuff (like Lou G. at LG Motorsports who is will be on TV racing Trans Am this weekend) recommend blank rotors to customers that will be hard on them.
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