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baz67
09-29-2004, 08:44 PM
Back to the drilled or not question. Tonight I was watching a show on the new C6 development and noticed, on the cars sent to Germany for the high speed testing, had drilled rotors. They were only drilled not slotted. I am in the thought of not using drilled rotors. It just may me go hum.
Brian

jonny51
09-29-2004, 09:22 PM
It seems to be a big debate lately.

Ralph LoGrasso
09-30-2004, 03:46 AM
I saw that show as well, Baz. Very cool show, indeed. I think they did mention however that the holes were cast in. Or was I just hoping they were cast in?

Gotta love the C6. This pick with the possible dark grey wheels they're thinking of releasing is incredible, I love the car in black. I can't wait to see the C6 Z06.

Chevyman73
09-30-2004, 04:09 AM
I am of the same mind, I don't want drilled rotors either. I haven't see a drilled rotor that hasen't spider cracked at the holes yet. I like SSBC's turbo slots the best of the rotors I've seen, but the Baer claw slot is cool looking too. Nascar sees some of most intense braking possible and you rarely see a drilled rotor it those applications. Sloting is very common though. :look:

http://66.70.234.198/forum/attachment.php?attachmentid=845&stc=1

Steve1968LS2
09-30-2004, 07:19 AM
Depends if they are cast in or drilled in.. also if they are chamfered (sp?).. A lot of high end sports cars come with "drilled" rotors..

Fuelie Fan
09-30-2004, 08:40 AM
One of the engineers admitted in one of the recent magazines it was more for show than go (or stop in this case, I guess). I can't remember which magazine it was. Last month when about 4 hit the newsstand all featuring the Vette, I stood in Vons for about an hour and a hlaf reading em all.

dennis68
09-30-2004, 08:58 AM
Not trying to stir the pot

:seizure: :seizure: :seizure: Yeah right. You are going to bring up drilled/slotted rotors and claim not to be poking at the hornets nest.

Ralph LoGrasso
09-30-2004, 08:58 AM
There was a show on the discovery channel last night all about the C6. It was entitled "Corvette - rebuilding an icon". I think that was the name atleast. Anyways, they didn't really mention anything about the cross drilled rotors to my recollection, but I do remember them saying something like "These are the most powerful brakes every offered on a corvette, and because of that they get very hot and need cooling". This was in reguards to the cooling ducts though, they were having a problem with the larger cooling ducts pushing the car up at high speeds, the smaller ducts they designed to remidy this resulted in brake fade, and they dismissed those. They never did say how they fixed the problem, or what comprimses were made.

Q ship
09-30-2004, 09:43 AM
Here's (http://frrax.com/rrforum/index.php?act=ST&f=2&t=2220&) an interesting linkabout C6 brakes. Notice that cross drilling isn't mentioned as a performance enhancer. Otherwise, I'm staying out of this mess. :hammer:

EDIT- This (http://www.corvetteactioncenter.com/) is the CAC referenced in the link above.

MrQuick
10-01-2004, 06:02 PM
I've got my ore ready...no stirring spoon here:
If drilled rotors are so bad the why have the motor cycle crowd use them still? Race ones too? Since what early 70's?

will69camaro
10-01-2004, 06:40 PM
I could be way off base and i'm by no means an expert but i think the motorcylce crowd can get away with it because they dont have 2000lbs+ of vehicle to stop. Those bikes weight in around 800lbs (sport bike) with a rider on it and the big cruisers still would come in less than a small car.

William

Q ship
10-01-2004, 06:49 PM
I've got my ore ready...no stirring spoon here:
If drilled rotors are so bad the why have the motor cycle crowd use them still? Race ones too? Since what early 70's?
Hi Vince. They use solid(non vented) rotors too.....
What works well for one is not the best for the other.

MrQuick
10-02-2004, 06:58 AM
you guys tryin to tell me bikes big are small stop differently than cars and brakes theories don't apply to bikes? Even if they don't weigh as much as cars the weight to power ratios to rotor size are almost equal.Makes you go, huuuummmm?

Kenova
10-02-2004, 07:46 AM
The rotors for cars are usually cast. It appears to me that bike rotors are machined from steel blanks, or have I been fooled by their shiny appearance? :hmm:
Ken

spanky the wondermuffin
10-02-2004, 02:33 PM
the force required to accell/decell an object rises exponentialy with speed and/or weight,not linearaly.it takes far more than twice the force to affect a mass that is twice as heavy.a motorcycle's rotors are much more exposed to cooling airflow.back in the day we would drag the front brake a bit towards the end of long straights to build heat before the brake zone.drilled rotors on motorcycles may be more for unsprung mass reduction.unsprung weight is most important as it compares to sprung weight.a couple ounces is a bigger percentage of the total on a lighter vehicle.as far a the c6 it probably has ac and leather seats-and that isn't to make it faster either.

yody
10-02-2004, 06:36 PM
my question has always been, and let me say NO ONE has ever given any kind of answer to this question besides "they do it because it looks cool" is if the crossdrilled rotors DO NOT work, Not if they crack or not, but if they do not work then why do the top of the line cars use them, as in Mercedes, Porsche, Ferrari, Corvette, and others use them, I doubt people buying SL55's, or plain old S500's(can barely even see the rotors) care if their rotors have holes in them or not. Same with Porsche. Regardless if they crack or not do they brake better? Also some of these companies were putting these rotors on their cars Before people thought they looked cool. I have seen that Baer supposedly did some kind of backyard test and said that the holes didn't do anything, but i don't think their test was a very good reproduction of brakes on a car. Also i don't think Baer brakes a company that doesn't really produce anything but "kits" is a reliable source. I think testing by companies like Porshce/Ferrari who compete in many performance/races would have better ways of testing and research. Now I am by far no means some kind of engineering genious, but it sounds like they could be a good thing, even if they are cast/drilled they are still doing the same thing, and the big question is if they help braking. I don't know the answer, I like the way they look so thats good enough for me.

dennis68
10-02-2004, 07:10 PM
Bottom line, even if the drilled holes were cast and didn't crack, the cooling effect would not balance the loss of friction coefficient. What is the point in installing "big brakes" if you are going to take 25% of the friction away with holes or slots or whatever. Might as well just leave the stock 11" brakes in place.

Chevyman73
10-02-2004, 08:02 PM
There has to be some sort of slot or hole to vent the gasses away from the rotor and pad to enhance braking. If you don't allow these gasses to escape they are going to cause a loss in contact between the rotor and pad surface anyway so you are losing your braking power there too. The best trade off is what we have to find. Here this is taken directly from Baer and Wilwood's FAQ section and should help stir it even more. :poke:

Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity.

Slots or grooves in rotor faces are partly a carryover from the days of asbestos pads. Asbestos and other organic pads were prone to "glazing" and the slots tended to help "scrape or de-glaze" them. Drilling and slotting rotors has become popular in street applications for their pure aesthetic value. Wilwood has a large selection of drilled and slotted rotors for a wide range of applications.

And here is what Baer Brakes has to say...
What are the benefits to Crossdrilling, Slotting, and Zinc-Washing my rotors?
In years past, crossdrilling and/or Slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads began to break down at extreme temperatures. This condition is often referred to as “green pad fade” or “outgassing”. When it does occur, the driver still has a good firm brake pedal, but simply little or no friction. Since this normally happens only at temperatures witnessed in racing, this can be very exciting!

However, with today’s race pad technology, ‘outgassing’ is no longer much of a concern. When shopping for races pads, or even ultra-high performance road pads, look for the phrases, “dynamic surface treatment”, “race ready”, and/or, “pre-burnished”. When these or similar statements are made by the pad manufacturer, the pad in question will likely have little or no problem with ‘outgassing’. Ironically more pedestrian pads used on most streetcars will still exhibit ‘outgassing’, but only when used at temperatures normally only encountered on the racetrack.

Although crossdrilling and/or slotting will provide a welcome path to expend any gasses when and if they develop, it is primarily a visual enhancement behind today’s often wide-open wheel designs.

Crossdrilling offers the greatest gas relief pathway, but creates potential “stress risers” from which cracks can occur. Baer’s rotors are cast with crossdrilling in mind, from the material specified, to curved vanes, behind which the holes are placed to minimize potential crack migration. Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings.

Sorry it's so long!

dennis68
10-02-2004, 09:07 PM
There has to be some sort of slot or hole to vent the gasses away from the rotor and pad to enhance braking. If you don't allow these gasses to escape they are going to cause a loss in contact between the rotor and pad surface anyway so you are losing your braking power there too.


In the old days (am I dating myself) drilled rotors rotors were used for outgasing. Todays brake friction components are much different than they were in days past. It is no longer nesessary for the rotor to provide a method for pad venting. The brake pads themselves provide that releif in most cases if the pad even has any build up to begin with. Todays materials like ceramic for one do not have the outgassing problems associated with high perfromance brakes.

If anyone has any tech to contrdict my statements I'm all ears, please cite sources (I do this for a living and "my buddies says" isn't going to cut it).

Baer and Wilwood have it right, another old racer technique (that isn't used anymore) turned into "bling" for the bolt on crowd.

Q ship
10-03-2004, 07:06 AM
Baer and Wilwood have it right, another old racer technique (that isn't used anymore) turned into "bling" for the bolt on crowd.
DING DING DING We have a winner!!!

Chevyman73
10-03-2004, 08:06 AM
I agree that both are more for show than function. Since most brake pads come with at least a single slot in them to provide some degree of relief for outgasing wether it's really need or not. I have plain C5 rotors for my Camaro and they won't recieve any type of slotting or drilling. If it were necessary though I would still rather have it slotted instead of crossdrilled though. :guilty: But Baer does say "Ironically more pedestrian pads used on most streetcars will still exhibit ‘outgassing’, but only when used at temperatures normally only encountered on the racetrack".

nancejd
10-03-2004, 08:12 AM
First let me say I really don't know what the answer is, but aren't we really talking about street pads being used at race car speeds? That's what the C6 is designed for too. I don't think most of our cars are going to be running race pads on the street, some will, but most won't. So if you are running a street pad, would there be a benefit to cross drilling or slotting? Or is it worthless in that application too?

dennis68
10-03-2004, 09:57 AM
Nothing about the C6 pad is street use. If you call the dealer in the morning the lowest grade pad they sell for any Corvette since the C5 was introduced is a ceramic pad. Bare is talking about true street pads, like Kragen 39.00 specials, being used on the track. Not more or less track pads that get used on the street.

yody
10-03-2004, 06:11 PM
actually i doubt that the C6 uses "race" pads. A true race pad needs to be cycled and heated up before it works effectively, and i doubt that GM could sell many corvettes if they told the owners that there brakes won't work effectively if they don't heat them up first! Also since you claim that
"another old racer technique (that isn't used anymore) turned into "bling" for the bolt on crowd." I guess Ferrari and Mercedes and Corvettes use them because they are still using old race techonology. And that Porsche engineers just merely are bolt on bling bling type of guys. Sorry Dennis i think youve been hanging around CC.com too much :)

Flyboy
10-03-2004, 07:19 PM
And that Porsche engineers just merely are bolt on bling bling type of guys.

They're not? :hmm: :)

baz67
10-03-2004, 07:42 PM
I promise I did not want to stir it up. :) We all agree that the brake system as a whole is one of the if not the most important safety system on our cars. Why would we put a part on them that has proven to fail. This is not just theory or assumtion. The thread from the old board had a few pics of cracked rotors. Now I am all for saving unsprung weight were I can, but I WILL NOT do it at the expence of safety. Even if it is a remote chance of the part failing. Remember Murphy's law. I will find better ways to save a pound or two.

As for why some other high end cars use them, all I can say if form over function. The typical buyers of these autos do not know the differance between a drilled rotor and thier... well you know. No the engineers are not the bling type, but the people trying to sell them are. I think the marketing department won on that.

There have been some studies on this and some will question them. However they all point to drilling rotors to be a neglegable benefit with todays pad compounds. Even if the testing was not perfect, it does point in that direction. That can not be discounted. We have some smart knowlegable people on this site. Why all of them have not chimed in is anyones guess. Maybe they do not know or just want to keep it a secret and watch us argue the point.

Brian

dennis68
10-03-2004, 07:51 PM
Yodi, FYI-ALL brake pads are supposed to heat cycled. Most owners just don't want to go through the hassle of doing it correct. And yes, Mercedes, Porsche, and however else are in it for the "bling" factor. Go to any high dealer (I work at one) and watch customers about potential purchases, they do climb around and questions like "why do the brakes have holes" and salesman answer "because they are high performance brakes". "Bling" sells cars.

Brian, the others you speak of had this argument so many times they are probably tired of it. It is tough to explain why something doesn't work when the biggest argument coming back is "well, so and so company sells them, or Mr. Bigshot car manufacture puts them on their cars". Mr. Bigshot cars also puts airbags and ABS on their cars, I don't suppose you want to retrofit your classics with those do you?

yody
10-03-2004, 08:14 PM
Dennis not to step on your toes or anyting and maybe i am wrong but i think there is a BIg difference between a chrysler customer and a Porshce/Ferrari customer, Also are you trying to tell me that Porsche and others are putting brakes on their car because stupid people will think its cool when the salesman tells them they brake better? I think that most people shopping for those cars already assume that the car is a top of the line sportscar and will stop pretty darn good, holes or not! Also the high end companies know that a majority of the owners will be occasionaly racing their cars, and what about people who drive on the autobahn? I don't have any answeres but i am not going to base my decision on a company that sells brake kits and a bunch of smart jerks on a website. But as i stated before i think they look cool, and since i haven't tried them before i will give them a go and see what happens.

dennis68
10-03-2004, 08:38 PM
Actually I was talking about the Mercedes cutomers and Lincoln customers, I work on Chrysler's but work at a Lincoln dealer and have worked at the Automall in Fremont (Porshce, Mercedes). How may snotty doctors do you think actually race their cars. I'll bet less than 2% of all new Porshce customers ever race thier cars.

yody
10-03-2004, 10:27 PM
valid point about porsche owners! Everyone in Marin drives a porsche, most of them probably haven't even taken the engine past 3000Rpm! One thing about porsches is that they have a lot of racing teams and are succesfull in many different competitions, companies like that have tons of R+D with some of the top engineers. I trust their R+D and their engineers over a "kit" company or people chatting on line any day, look at Ferrrari, they even have drilled rotors on teh enzo, although it looks lke they are using Ceramic rotors! So if ceramic doesn't need venting then why does their ceramic rotors have holes. It just doesn't make sense. And saying that the only reason Ferrari puts drilled rotors on their top of the line million dollar super car is because the people who buy them will be tricked into it just doesnt fly with me, especially since they sell themselves! Also if venting brake gasses is an old trick from long ago, then why do many Nascar cars run slotted rotors? and why do people say that drilled rotors aren't good but slots are but that you don't really need to vent new brakes?? sounds like a bunch of hipocracy and no one really knows what they are talking about including me.

dennis68
10-04-2004, 05:33 AM
We know Cody, I'll just leave it that. You go ahead and continue to beleive that if Ferarri does it then it must be the thing to do.

Fuelie Fan
10-04-2004, 09:08 AM
the force required to accell/decell an object rises exponentialy with speed and/or weight,not linearaly.it takes far more than twice the force to affect a mass that is twice as heavy.a motorcycle's rotors are much more exposed to cooling airflow.back in the day we would drag the front brake a bit towards the end of long straights to build heat before the brake zone.drilled rotors on motorcycles may be more for unsprung mass reduction.unsprung weight is most important as it compares to sprung weight.a couple ounces is a bigger percentage of the total on a lighter vehicle.as far a the c6 it probably has ac and leather seats-and that isn't to make it faster either.

An objects energy does rise linearly with respect to mass, but quadratic with respect to speed (KE = 1/2 m*v^2). Therefore, brake sizing for energy dissipation would be much more strongly tied to a vehicle's top speed than to it's mass.

I don't think anybody was saying motorcycles have different laws of physics. The point was that motorcycles have completely different design criteria becuase the positioning of the rotors in freestream air means one can expect completely different heat transfer rates TO that surrounding air, which is really the limiting factor to rotor mass determination. This is why they don't need huge vaned rotors. It is probably also why they can swiss cheese the heck out of them for weight savings. Recall: Ffk (force of kinetic friction) = mu_k (coef of kinetic friction) * Fn (normal force). There is no area requirement. Removing surface area therefore does not reduce available braking torque.

I don't pretend to have any answer as to whether drilled rotors actually increase braking potential, what the effects of different pad materials are, outgassing, etc. All I know is I've seen a few pics of cracked rotors, I don't really want "the look" that bad, I don't need the few hundred grams of weight savings, and based on that reasoning I plan to use undrilled rotors.

yody
10-04-2004, 09:29 AM
Dennis is it me, or do i just love poking you in the ribs? :box:

dennis68
10-04-2004, 10:50 AM
It's you.

baz67
10-04-2004, 02:36 PM
I don't pretend to have any answer as to whether drilled rotors actually increase braking potential, what the effects of different pad materials are, outgassing, etc. All I know is I've seen a few pics of cracked rotors, I don't really want "the look" that bad, I don't need the few hundred grams of weight savings, and based on that reasoning I plan to use undrilled rotors. :git:

Well said. I guess that was the point I was trying to make. Man and I was not trying to start any fires.
Brian

yody
10-04-2004, 09:28 PM
hey dennis, wasn't your car a nice white before?

dennis68
10-05-2004, 05:29 AM
:wedgie: :getout:

baz67
10-05-2004, 12:58 PM
Ok after many hours doing more research the answer may be.... Wet Rotors. It seams that some other high end German sports car manufacture mentioned earlier states that the holes help let water vapor or steam escape. That kind of makes sense to me. They were testing in Gemany. I guess we will see if the production version has them.
Brian

StRacerDuke
10-06-2004, 06:20 AM
My personal choice in brakes would be the drilled and double slotted stainless brake lines. I hear they work great on the track. :woot:

David Pozzi
10-08-2004, 12:47 PM
Everyone doing ok here?
Just checking... :slap:
David

dennis68
10-08-2004, 01:04 PM
Thanks for "checking up" David. Yeah, we're fine. Yody has "wedgie" coming to him but he will recover.

David Pozzi
10-08-2004, 10:33 PM
I wish there were an unimpeachable authority to question on this subject and put it to bed for a while. Lots of opinions on the web.

I DID notice the Trans Am race cars at Laguna Seca didn't have drilled rotors, but they DID have water spray systems in the brake ducts! :secret:
But don't tell aybody...
David

harshman
10-09-2004, 08:49 AM
I wish I worked on my car as much as I talked about it. :lmao:

Conekiller13
10-10-2004, 11:17 PM
It's as simple as this............if all out performance is what You're after look at race cars. From the top at F1 to bottom of the barrel at nascar.........no cross drilling. Carbon/ceramic or iron no drilling in racing aplications anymore but slotting is widely used. Drilling is done on Porsche's and Ferrari's because it looks racey and they have an image to uphold. If You want usefull cross drilling look at motorcycle rotors. That's done to reduce rotating mass and gyroscopic effect.....very important on a 400lbs bike.........not as important on a 3600lbs car.

Conclusion.........Holes=bling, slots=function

yody
10-11-2004, 10:34 AM
according to who? you? what testing have you done? I am just to stubborn to believe, because a select amount of people on the internet believe this that it is true, and i bet you almost 90% of the people saying it did not think this earlier this year. people tend to be trendy and believe whatever they read. So just because a few people on canyone carvers said so, doesnt make it true. However I could really care less if they Don't do anything. I have no stakes in crossdrilled rotors, i am just not following the crowd.

dennis68
10-11-2004, 11:09 AM
:hand: Hey Yody, you want testing. Call Hendricks Motorsports or Joe Gibbs Racing and ask them why none of their cars have drilled rotors. I'm sure since they SOOO good that maybe they don't know about them yet. :hand:

yody
10-11-2004, 11:27 AM
since when do any of us drive complete race cars? THey probably dont use them because the crack.

Q ship
10-11-2004, 12:27 PM
according to who? you? what testing have you done? I am just to stubborn to believe, because a select amount of people on the internet believe this that it is true, and i bet you almost 90% of the people saying it did not think this earlier this year. people tend to be trendy and believe whatever they read. So just because a few people on canyone carvers said so, doesnt make it true. However I could really care less if they Don't do anything. I have no stakes in crossdrilled rotors, i am just not following the crowd.

Classic.

dennis68
10-11-2004, 01:24 PM
since when do any of us drive complete race cars? THey probably dont use them because the crack.

Yeah but I drive it like it's a race car-just ask Vince. :drive:

yody
10-11-2004, 01:45 PM
How about this then, if crossdrilling doesn't do anything to enhance braking because pads don't need the "degassing" and that is an old myth because brake pads thesed days don't need it, then why do slots help at all??? Heres my problem here, there is no real tech here, i have seen/and read the tech at CC.com but all it really was was a couple of engineers griping at each other. Nothing being said really makes sense it is all theorys and everything contradicts each other. It really isn't that big of a deal. If someone met me, and questioned the rotors, i would probably reply that i wasn't sure if they really did anything or not, but that i like the way the look. Its just funny to me that nobody really has any evidence. If slotting is on nascar then there is a reason, most likely; better braking,less fade, helps get rid of the gases, why not cross drilling? they cause cracks when abused, do crossdrilling work? probably so if the slots do, will they crack if you put them to extreme racing?maybe. On a mostly street car I don't see any disadvantages, and if you guys think that slots work then i don't see how you could contradict yourself and say that holes are for bling bling. And then there is my theory about Ferrari/Porsche/and mercedes. You guys keep saying that Ferrari and Porshce do if for looks, but never mention why Mercedes does it on their S500, where you can barely see the rotors.

harshman
10-11-2004, 02:07 PM
I think I might simplify things a bit. My main reason, and I am sure others as well, is that cracks and potential breaks on a rotor at high speeds is not a good thing no matter how well it performs or looks. For those of us who have worked with metal extensively know what severe heat will do to steel. If I have two rotors in front of me one is drilled (be it cast or drilled) and the other is not, on race day, I will always go for the one that isn’t because it will work and I won’t have any safety concerns. Because all the big sports car guys are doing it is not an issue with me – keeping my car together is. To be honest, the calipers and pads will affect the same on a regular rotor or a cross drilled one and so performance is not an issue here in this argument. Show me one cross drilled rotor and I will show you 5 that have the same performance characteristics. After all, this is aftermarket products we are talking about here. We all want the best but for the most part, we will not sacrifice safety over anything.

dennis68
10-11-2004, 05:50 PM
Yody, are you kidding???? I think my first reply had all the tech you need. Drilling removes removes friction area from the rotor-there is good tech that is undisputable and worsens braking performance. Drilling holes in rotors changes the grain flow of the material when it heats up causing metalurgy problems with heat transfer. Drilling holes in rotors does induce a problem with cracking that would not otherwise be there.

Do I think they look cool- :icon996: , yeah especially the 2-peice Baer Eradispeeds. Will I ever run them, no.

yody
10-11-2004, 08:23 PM
oh, so do tell us, where do you get this info from?......let me guess...... CC.com??? sounds good, but of course anything that techincal sounds believable to someone who isn' an expert as myself. I know i am being an arse here but i guess i am playing devils advocate. So you are going on your info and facts based on some unknown canyon carvers Genious that came up with this stuff? or race oriented companies that are responsilbe for thousands of cars sold to the public, that can be held liable if all their rotors suddenly cracked and fell apart. Also show me a crossdrilled rotor that actually cracked and became a safety issue, i have seen the pics with the spiderweb cracking and one of a hairline crack in it. Obvioulsy those aren't safe but there still haven't been any accidents that i have heard of. Also if holes reduce the surface area then what to slots do??????? more contradictary. Let me ask you guys, if I had an engineer that you had never heard of come up with a valid "sounding" story with lots of "techincal talk" that was in favor of drilled rotors, would you change your mind and admit it??

dennis68
10-11-2004, 08:40 PM
Yody, you will never find an engineer who will be able to contradict any of my points with any kind of valid data. No, they do not come from cc.com-I just found that site in the last few months. Yes, slotted rotors also reduce friction surface just not to the same degree. Slotted rotors also do not suffer from the same metalurgy problems associated with drilled rotors, if the slots were say every 1/2" we see or more pronounced concern. Actually most of points require little more than basic automotive/brake experience to form on your own. If you understand how brakes work than it is impossible to ignore that cutting away part of the rotor reduces total friction surface area and is no different than using smaller brake pads. I don't know of any race oriented companies that produce drilled rotors (Baer is certainly not race oriented, and even they admit that drilled rotors do nothing toward improving braking performance).

Just curious, is the goal to see if we can re-hash the same over and over until the thread has like a 100 responses?

jonny51
10-11-2004, 08:49 PM
only 46 more to go!! :)

yody
10-11-2004, 08:50 PM
whats the count at? :) Well at least i got you thinking! I agree to agree that there can be some probability in your points, it is still not enough info to make me go for it, I also don't think people should be stating things that have not been proven. From the begining I never was really for or against either type of rotor. I still am not convicned, but agree that drilled rotors are not a sure thing. Well we will see if i can crack my rotors.

dennis68
10-11-2004, 09:20 PM
Yeah, I'm thinking alright. Thinking about which orifice of yours I should stick my size 13 into. :rotfl:

Q ship
10-12-2004, 06:33 AM
Also show me a crossdrilled rotor that actually cracked and became a safety issue, i have seen the pics with the spiderweb cracking and one of a hairline crack in it.

Well, the link in the first post on this forum (http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=23;t=000401) is dead, but it had a video and pictures of a failed, cross drilled rotor on a BMW 3 series. The failure originated from the holes, it was pretty obvious. Of course since the link isn't there any more, it never happened, right Yody? :rolleyes:

Whatever, it isn't like this is some ground breaking thread, check the dates on the link I posted-and it was tired then. I get the feeling that you will never be convinced, Yody, and I feel silly for arguing on the internet. So good luck to you. I'm out.

Fuelie Fan
10-12-2004, 08:25 AM
Drilling removes removes friction area from the rotor-there is good tech that is undisputable and worsens braking performance.

F_fk = mu_k * F_N
F_fk = Frictional force, kinetic (which is basically, given rotor dia, your braking toque)
mu_k = coefficient of kinetic friction
F_N = normal force

F_N = fluid_press*A_pis
Fluid press = pressure in braking system
A_pis = total area of caliper pistons

I don't see pad area in braking "performance". Durability maybe, the smaller pads will wear out sooner I suppose. but, drilling does not decrease pad area, so that's a null point.

Still not saying I support either of your views, just playing devil's advocate, I'd like to see a rebuttal to the basic math.

dennis68
10-12-2004, 08:54 AM
Pad area very much plays into braking performance, the same way pad composition does. Nice try though, throw the 3rd year engineering major-math out there to confuse the point-almost got me.

Only 40 to go.

yody
10-12-2004, 09:28 AM
qship how are you arguing? you haven't put any information out there?? or really said much at all on this thread. I feel the same way you do, that you won't ever change your mind. I think the crossdrilling being bad thing is an internet trend, and most people are just going along with it.(I do appreciate your input on my rear brakes though :) Well see ya guys on other posts

Zefhix
10-12-2004, 09:58 AM
:enguard:


Best thread ever :bananna2:
38 to go; I wanted in somehow...

Fuelie Fan
10-12-2004, 12:48 PM
[QUOTE=dennis68]Pad area very much plays into braking performance, the same way pad composition does. Nice try though, throw the 3rd year engineering major-math out there to confuse the point-almost got me.QUOTE]


Okay.....care to elaborate as to how? Again, not saying wrong or right, but you offered really nothing to substantiate other than "it just does". I'm totally not a braking expert, so I'd like to hear the explanation.

Pad composition most certainly affects mu_k, and also how mu_k will change with temperature. I agree 100% on that point, but you can't just make an arbitrary connection between pad material and pad area.

A quote from another site that I came across purely by accident today (I swear I made my post before I read it):

"Coefficient of friction does not depend on surface area, but rather the friction value, multiplied by the force applied (by the caliper pistons to the pad). Surface area has a lot to do with pad wear, or think of a rotor that has a ¼" swept area. It will still stop the car the same amount, but the pads won't last as long."

Seems to support that derned engineering crap that nobody wants to believe

dennis68
10-12-2004, 01:16 PM
In a stone cold braking contest I would agree that brake pad size has little to do with stopping distance, however I am not aware of anybody who operates their brakes under those conditions. Since a larger surface area is more capable of disipating heat and heat is the leader in brake fade, it stands to reason that under normal operating conditions brake pad size doea have a substantial impact on stopping distance. Sorry, I don't have a formula to show how this works and I actually don't use them at all for the most part, practical application wins over text book everytime. :icon996:

Fuelie Fan
10-12-2004, 03:15 PM
That seems reasonable.

BUT, does this argument directly apply to drilled rotors (which was supposed to be the focus, I think we got slightly off-track)? A thought experiment says that the holes provide no area to create and conduct heat (which is what braking is, Kinetic to thermal conversion), or in other words the contact area has been reduced. At first this seems to suggest that it would act in the same way as a reduced pad area. BUT, I have to wonder what is going on at the unused portion of the pad at any instantaneous second. Also, it is not like the holes are circumferential; they pass through the pad, and are followed by solid material. So how does this affect things? It does not seem entirely unplausible for well placed holes to allow the brake pads to perform as effectively (or at least as far as the a moderately skilled driver can tell) as if they were against a solid rotor.

I tend to lean toward the holes not reducing braking performance nearly as much as physically removing material from the pad. Either that, or I don't have a good mental image of how much "equivalent area" each hole removes. You could do a ratio of areas (solid vs drilled) perhaps, then decrease the pad on the solid rotor by the corresponding percentage? Would that be equivalent?

harshman
10-12-2004, 03:21 PM
yup! now i got a nose blead.

Fuelie Fan
10-12-2004, 03:23 PM
Oh, and it bugs me when people say things like "practical over theory". Just about everything can be accounted for with an accurate model. I guarantee the pros HAVE theories and equations that precisely explain what we're talking about, it's just we don't know about it. So really all that statement says is we don't know enough yet to account for what we've seen.

the best exception: tires. They're incredibly complicated. But the science is getting better and the mathematical models more accurate every day.

dennis68
10-12-2004, 05:51 PM
Yeah Firestone and Goodyear know all about building better tires these days. Yes, I have worked for both and have done my share of tire recalls. My point was that theroy is good to get the mind thinking but you can never plan for practicality on paper. I deal with DCX engineering on this all the time, they design , and it's good until you try and put it to use in a real world enviornment. That when I get to re-design to work correctly.

yody
10-12-2004, 11:36 PM
So Dennis, since you are such a real world type of guy, what kind of real world testing have you done? I know I have been stepping on your feet this whole post, but it seems as if we are representing to differnet sides of an argument or should i say discussion. The only reason why I ask you for testing data is that you are making a point that holes do not work, I am merely questioning that theory. If I was to say They definetly do work, I would have to back up my presumption with hard facts and data which i don't really see here, I mostly see people just getting irritated because I am not going along with their ideas. All I see is bland statements with no real facts to back it up. The only real problem with these engineering discussions is that it seems so easy to argue back and forth and find loop holes in peoples ideas, kinda like Kerry v Bush. One person is always going to think the other way and there is no way to convince them otherwise. Basically this is a good discussion. THere isn't going to be any for sure answer. I just think that people should not state things that they overheard somewhere else, and state them as a fact here, because that is the new trend to go along with. I am not pretending to know much at all here, just exploring a different side to these theorys. Well maybe we can agree that there is no for sure answer. I guess it would be pretty hard to do a real world test to see how they helped in brake fade. I don't think a test like Baers is sufficient, i believe all they did was put the brakes on a fixed machine spin them up fast, apply the brakes and thest the temperature output, I don't think that replicates real life standards, where you have a weight of a vehicle and brakes inside of a wheel next to a hot engine, and the acceleration of a car to stop

jannes_z-28
10-13-2004, 04:51 AM
Haven't read all posts in this thread yet but I will throw in some thoughts anyway.

Here is a link with some facts:
http://www.apracing.com/car/brakedisc/face.htm

THis site has a lot of brake information, AP Racing is one of Europes leading high performance brake supliers. they have a few Formula One teams as their customers.

You will find a lot to read here.

So what do they say about drilled rotors?

"Mainly used for aesthetic reasons on road applications."


I guess the last word on this will never be said :-)

Jan

streetfytr68
10-13-2004, 05:10 AM
I can't take this **** anymore!! This isn't one guys opinion vs. another. This is BASIC Physics. What's the problem? Need some proof? You don't need brake manufacturer or sports car maker. Go to any high school physics textbook and look up the chapter on The First Law of Thermodynamics. Search the entire internet.

If you take two identical solid rotors--no make that solid OBJECTS (same, material, dimensions, features) and drill holes in one of them, the drilled rotor--I mean object's-- ability to ABSORB HEAT will be lower than it's solid counterpart. The little metal shavings on your work bench resulting from the drilling process represent LOST MASS. Mass is a fundamental component of the heat absorption equation.

THAT'S ALL. THAT'S IT. ASTA LUIGI!

So, given identical circumstances, the solid rotor will always work better because it can absorb more heat.

Does that mean that drilled rotors are junk? No. As long as that drilled rotor is used in an application that does not EXCEED IT'S ABILITY TO ABSORB HEAT, it's fine. Any rotor--drilled or not--will warp or crack when it's heat capacity is exceeded. But the otherwise equivalent UNdrilled rotor has a greater capacity to absorb and is therefore less prone to failure under identical circumstances. WHY IS THIS SO HARD TO UNDERSTAND?

My hot rod has Baer drilled and slotted rotors because they they reduce unsprung weight and look cool. I can take advantage of the looks and weight reduction every day on the street.

So in case I have lost you, solid rotors are better than drilled rotors. A drilled rotor is entirely effective and acceptable when the system and circumstances in which that rotor is used does not exceed the rotor's capacity to absorb (and dissipate) heat. At any given time, you can plug a solid rotor in place of that drilled rotor and extend that otherwise identical system's braking capacity. See? All that and we never even had to touch the Second Law of Thermodynamics!!


Yody,
One of life's best lessons is:
Disagreeing for the sake of argument does not make you any more intelligent or wise--nor does it make you appear any more intelligent or wise to others. :hmm:

Search:
-Specific Heat Capacity
-Heat Absorption
-First Law of Thermodynamics

dennis68
10-13-2004, 05:57 AM
:lol: :lol: :lmao: :lmao: :lmao: :rotfl: :rotfl: :rotfl:

It may take a while to recover.

streetfytr68
10-13-2004, 06:15 AM
Now now Dennis. I'm not trying to flame him. I'm 37 and I just learned that lesson like, 3 weeks ago. (Not the thermo's--the other one.) I'm just sharing the wealth and spreading the love.

Norm Peterson
10-13-2004, 07:42 AM
If you take two identical solid rotors--no make that solid OBJECTS (same, material, dimensions, features) and drill holes in one of them, the drilled rotor--I mean object's-- ability to ABSORB HEAT will be lower than it's solid counterpart. The little metal shavings on your work bench resulting from the drilling process represent LOST MASS. Mass is a fundamental component of the heat absorption equation.Scanning through this thread, this seems to be the first real mention of heat capacity. It's not simply that the shavings on the bench represent heat sink mass that's been intentionally thrown away - it's mass that's been discarded precisely from where temperatures and rates of temperature change are going to be the highest. So you must absolutely expect rotor swept area temperatures to increase by more than the mass of shavings relative to total rotor mass would suggest.

Now let's talk heat flow. This is a far more complex issue than static snapshots of temperature over the rotor area (volume?). The time element is involved, and the rates of temperature change matter. In addition to being very sensitive to the rate of temperature change, these thermal transient terms are highly sensitive to local geometric discontinuities. And increasing the magnitudes of these goes to reducing fatigue life. Need I mention the connection between fatigue and cracking? Or only that pad coefficient of friction is not constant even over the range of temperatures encountered in street driving?

By way of explanation of thermal transient effects, the total picture can be reasonably well distilled down to the evaluation of three separate effects that are functions of the material properties (heat conductivity, specific heat, expansion, etc.). One is a linear temperature distribution through the thickness of a given part. Another is a nonlinear component of temperature distribution through the same thickness of the same part (this is a peak stress effect, and is the first of these three to reach its max value). The third is the effect of the difference in average temperature between adjacent sections of different thickness or between similar thicknesses subjected to different rates of temperature change (this one peaks last). I spent a fair part of my 20+ years in the nuclear power industry making evaluations that included precisely this sort of stuff.

At least slots don't interrupt the radial heat flow path even though they do increase the thermal effects (but with a professional race team budget I'd be discarding rotors far more frequently than I would care to on my daily driver or auto-X car).

I'll quote something I posted over two years ago (partly because I'm too lazy to retype it and partly to illustrate that there's more than one brake tech thread over at corner-carvers.


Quote:
Originally posted by jp99gt
. . . It would be interesting to make a finite element model of a rotor and dump the heat energy in at different rates, like 2.5, 3.0, 3.5, ... 5.0 seconds and see the differences in thermal stresses. Maybe I'll run a solid rotor problem for simplified geometry and see how it works out.

--Jim



I think you'd eventually end up modeling the vanes and the holes. The thermal stress terms are quite sensitive to geometric discontinuities (local thickness changes as well as the presence of the holes) and the rate of heat input. Remember also that there's more energy to be dissipated from the first 10 mph of decel than from the last 10, so with constant deceleration assumed the thermal effects will be more severe during the early portion of the event.

With that in mind, perhaps the more aggressive pads are putting yet more heat into the rotor early in the event even if the total duration of braking remains about the same. IOW, the early deceleration with them is higher than before, indicating that the assumption of constant deceleration isn't entirely accurate. This makes the thermal transient event more closely approximate a step temperature change.

Re upscale Euro cars w/drilled rotors - I suspect that their owners tend to fall into two categories. Those who will never tax their brakes sufficiently to cause problems to surface, and those who can/will replace rotors with no more thought than that given to replacing spark plugs.

Norm

dennis68
10-13-2004, 09:02 AM
Ah, c'mon Norm-I had the heat capacity affect nailed back in post 52 and again in 64. Albeit not as elequently put as Steve, but the same principle.

I promise to encourage Yody anymore, I promise to encourage Yody anymore, I promise to encourage Yody anymore, I promise to encourage Yody anymore, I promise to encourage Yody anymore, I promise to encourage Yody anymore......
Sorry my wife is a teacher, says I have to write on the screen a hunderd times not to encite a riot anymore, I figure that was close enough. :evil:

yody
10-13-2004, 09:06 AM
SO after all that mumbo jumbo, do holes have any benefits to brake fad/performance?
BTW steevo, i am not arguing just for the sake of argument nor to look smart, maybe that is a trait of yours? I just don't see sufficient info, just self proclaimed braking genious's stating things with no backup. Obviously Norm is a very educated person, and knows his physics, but maybe i didn't rear or undersatnd correctly, but I still don't see an answer to if holes work or not. and it seems even the genious's can't come up with a solid reason why These expensive cars use them. I guess all of their R+D in racing and 50+ years in teh exotic high performance market and racing has resulted in them putting brakes on cars that give up performance for looks? I will admit that lately in some of these posts there has been some better info, enough to make me even more vague on what the real answer is. It one respect I do agree with Dennis, people tend to over anaylize things in their head than putting it to the road.

immrtransam
10-13-2004, 09:21 AM
WHEW I never thought I would finish reading this post. As far as I know as far as motorcycles are concerned the holes on brake rotors are for cooling(greater surface area) and to help shed water. On my 1975 Suzuki GT750 the rotors were solid, and on the front fork leg was a warning sticker saying that "in wet conditions braking would be effected ". the next year they had drilled rotors and no warning stickers.

Plus they look cool :grouphug:

yody
10-13-2004, 09:27 AM
by the way, don't beat me up at sema :help!: :crying:

jannes_z-28
10-13-2004, 10:18 AM
Without knowing for facts I think that the European "hot cars" that have drilled rotors do have that more as a marketing feature than anything else. It makes the cars look racier and faster. People think it looks cool. I think that almost everyone driving those cars never will brake so much that it will hurt the heat-transfer or warp the rotors.

I'll bet that the engineers lost the battle to the marketing guys on this one. Drilled rotors sell better.

Everyone follows and think it is a good thing because Mercedes have it. In the auto industry there are a lot of "followers" that follow without knowing why.

I heard this story once, it is supposed to be true.

In the sixties one English factory motorcycle racing team constructe a fuelpump that got its movement from the rearsuspension. It reduced weight over the conventional setup. However to make the engine start the mecanics had to run behind the bike and jacking the rearsupension so that the engine could start. Of course they won the race.

On the next race all the other teams did the same thing, jacking their rearsuspensions in the believe that the first team had done this to warm up the shocks and therefore had an advantage.

This is an example of how easy it is to do things that others do without knowing why.


Jan

Norm Peterson
10-13-2004, 10:22 AM
SO after all that mumbo jumbo, do holes have any benefits to brake fad/performance?Not unless you have pads that significantly outgas and then drive such that you make them do so.



. . . but I still don't see an answer to if holes work or not.In that respect, the answer is "it depends". With cheapie pads (and relatively small OE-size brakes) it's quite possible that you could improve fade resistance somewhat, though that would come at the expense of increased likelihood of cracking. First stop performance would remain about the same, plus or minus whatever the temperature effect over the time duration of the stop (temperature time history of the pads & rotors) has on the coefficient of friction and whether or not the driver can accurately correct his pedal pressure continuously to suit.

Fatigue life is a complex thing to estimate, as it's a function of how severe each stress cycle is and how many there have been. It's an extremely nonlinear thing, BTW. The quick and dirty estimate that I'm most familiar with is that fatigue life is approximately an inverse 5th power function of alternating stress intensity. The simplest example that I can think of is to assume that you have a rotor that's good for exactly 100,000 cycles at some thermal stress intensity. Then double that stress intensity. It's now only good for around 3125 cycles, or around 3% of what it was good for at the lower stress level. Fortunately for us all, most street usage is at some small percentage of the 100,000 cycle stress level, so the cycles in actual service go into the millions.

Norm

streetfytr68
10-13-2004, 11:58 AM
SO after all that mumbo jumbo, do holes have any benefits to brake fad/performance?


In that respect, the answer is "it depends". With cheapie pads (and relatively small OE-size brakes) it's quite possible that you could improve fade resistance somewhat, though that would come at the expense of increased likelihood of cracking.



So for the purpose of a Pro-Touring car--where quality parts are generally specified in an effort to improve performance,

the answer is: NO

The cute little holes do not offer any benefits to brake fade/performance

34X2Camaro
10-13-2004, 08:51 PM
Everything went blurry after post #60. :rolleyes5

MrQuick
10-13-2004, 10:18 PM
heres how the guys on the american Lemans tour were using to take care of pad clean up and out gassing.They are cute too... Notice how they dont span the entire rotor. I spoke to one of the pit guys and he said slotted or not, stress cracks are common. Rotors and pads were exspendable. There were piles of cracked rotors and burnt up pads at every pit.

yody
10-13-2004, 11:39 PM
I have seen those type of rotors with the short slots on a Nascar car before, they seem pretty popular, whats the count now? :)

David Pozzi
10-15-2004, 08:02 PM
Hey, if I could get those bullet-hole decals made really really small, then sell them to the guys who want drilled brake rotors, I'd make a fortune! :)

But first, I need to figure out how to keep them from rubbing off! :hmm:

jeffandre
10-16-2004, 10:32 AM
Since I will be primarily on the street I am not worried about drilling or slotting a this point. I got a great deal on my Eradispeed II's, 13", which are on the rear. When I finally get to the front, which will be under a great deal more stress (with the accompanying heat) there will have been a lot more testing done on this subject and I will take advantage of the knowledge. Again I my 71 Camaro will be 99% street, with the rest at Thunderhill (relatively close and no weird elevation changes in corners like Infineon, which is even closer to me so I may check it out a few times too). I will keep watching this thread and others related to the subject in order to make certain I have the necessary information when the time comes for the front.

Again I would venture to say that most of the street cars on this site (many of which will see minimal track time other than open track days) would probably do just fine with whatever type of quality rotor used. Pure race cars or those that spend many consecutive laps under stress would be better of going with tried and true competition systems, which seem to leave drilled out of the picture for the most part.

Jeff

baz67
10-16-2004, 05:26 PM
The problem David is that after all of them melted off it would be just some glue and plastic goo on the rotor. Well wait one glue is adheasive right? You may be on to something David. We will call it PozziHoles, the cheap easy way to improve the stopping of your car.
Brian

mar3
10-17-2004, 06:53 PM
Well, here's my two cents...with a 2500 lb daily driven 1stgen RX-7, I experienced no cracks or "spidering" on my cross-drilled rotors at all and that's with whopping 8.94" diameter rotors...lol...I took factory fresh rotors to a local machine shop that's been around for 30+ years and drew the pattern I wanted on them. They decide where and how much material to actually take out to give me my cross-drilled pattern. These same rotors also saw some autoX workouts during that time. I'm sure it was more like the pad upgrade I did at the same time, but I definitely didn't have to worry about brake fade after the changes...here's a shot of the rusty beast about a year later after the accident that took that '80 Rx-7 off the streets...it sat in my driveway unprotected as I picked off the parts needed to build Furious Rex, the '83 RX-7 which is now my daily driver....absolutely amazing what a new Caddy can do to a poor old rex in the rain...

yody
10-18-2004, 08:42 PM
not to argue, but autocrossing wouldn't get your rotors hot enough to make them crack. poor little rx7