JerkyBoy

Ok, we need to end the comparisons with radiators and brake rotors, there are some very basic things which are close to the same, but the way they work is totally different.

It doesn't work because the cooling properties of water is far different than anything in your brake system. Again the cross drilling adds maybe 4% surface area to the rotor, that is not going to equal a lot of cooling - it probably won't even make up for the extra heat that the rotor is going to deal with because of the loss of mass. Besides that nobody has yet made a cross-drilled radiator

It's not cooling that the extra mass adds, the cooling effects come from surface area as you have mentioned. However, if something has less mass it will get hotter assuming we are comparing the same material in the same size, etc.

So why the mass? Well when you jam on your brakes real hard, the temp goes skyrocketing up...this is what it's supposed to do. Convection cooling will not be able to keep up with the sudden demand, so that heat has to go somewhere before the pad and fluid over-heat and you get fade. And this braking can happen for extended periods of time, like when you are ripping down your favorite twisty section of road. Just to use some random numbers, when just driving down the street your rotors may be sitting at 150-200 degrees (they are sitting close to a bearing, and maybe a little rub, etc)...but hit the brakes and those temps can go to 500 degrees + real fast.

Using the radiator example, how well would the radiator work if all the sudden it was asked to get rid of massive temp swings, whatever your normal cruising temp is, say 180 degrees, and then you jump on it and the temps soared to double that, would your radiator be able to keep up?

Well I don't disagree here for the most part, water is a much better way to cool an engine than air. But surface area is wrong. Compare a 1.6l VW engine from say a Beetle (the old ones) and a new 1.6l engine. The amount of area exposed to air is HUGE compared to the amount exposed to water. Everything on a bug engine is exposed to air, the cyl liners, the heads, the block...then mix that with a huge fan to blow air on it. The reason why water is the way to go is because water is much more effecient than air at pulling heat out of something. Hence why all modern air cooled engines have been the "flat" layout, because you can have cooling on all sides...with a huge amount of surface area.

Look at the guys that hot-rod their PC's, I can get a CPU fan that has a HUGE amount of surface area, and I can blow big super-fan on it.....yet a tiny little block of copper and run water through it will yield better results.

Again, that has nothing to do with brakes, because nobody has made a water cooled brake system for the street.

I've never seen a 747 pimping cross drilled rotors though.

Well now we're entering another arena.

But as I've said, I'm not arguing the point about surface area doing the cooling. I'm arguing about the point about drilling holes and how little tiny effect it will have on cooling, if you know somebody with a drilled rotor that can make some measurements we can find out the exact increase in surface area. But it won't be a very large percentage (again doing the math on a hypothetical example led to a sub 4% increase, we knew the number of holes...but didn't know the size of the holes).

Which then leads to 2 items;
Reducing mass, even if it's a small percentage will create an increase in temps (again it may be a small amount). Will the small increase in surface area make up for the loss of mass in terms of temps is the big question.
And more importantly, by drilling (and to a lesser extent casting) holes into a cast rotor you are weakening it. Which causes the cracks around the holes. To a much lesser extent you are also reducing the amount of the rotor that pad contacts (but this is going to be in the 1-2% range I bet - basically not noticable). But the reliability is the big one. You are doing very little to add to the surface area, but you are adding a lot to the possibilities of having problems with your rotors.

mar3

iTrader: (8)

Bad product or bad machinesmith....them's the breaks. My cross-drilleds are rusty as crap, as you might expect since they're sitting outside and not used anymore, but there no signs of cracking anywhere.
That's what happens when you buy a quality product and use a machinesmith that knows how much material to remove and how to remove it so the metal grain structure or temper is not compromised. Sorry you got ripped off, man....

Manntis

Alright. While we continue to disagree on the benefits of crossdrilled rotors, we agree that increased surface area is beneficial for cooling. I must have misunderstood your initial assertations as they seemed to imply that mass, not surface area, provided the heat sink. If the misunderstanding was mine I apoligise.

Your VW model is a bit flawed, as only the outside of the engine is exposed to air in a relatively small engine; but that's a side point. I understand the principle of what you're saying, and there are arguements for/against.

747s only brake for one stretch (landing) per several hours. The logic behind cross drilled rotors is repeated braking such as you'd encounter at LeMans.

Now that we're sticking to information, we're partially in agreement and that which we disagree on (my assertion that crossdrilled brakes cool faster verses yours that it provides maybe 4% increased surface area and the benefits are false, if I am stating your arguement correctly) are among the myriad of common disagreements when it comes to automotive opinions (i.e. the benefits of airbags, brute horsepower vs. maneuverability, etc.)

Thanks for the discussion. While I continue to believe based on the evidence I've experienced that crossdrilled rotors cool faster than solid rotors, I now take into account the evidence you present concerning the structural integrity of same.

JerkyBoy

They were actually Brembo branded pieces with chamfered holes and everything. They still developed the cracks....now don't get me wrong, the cracks weren't anywhere near the critical level...but it certainly wasn't going to get any better either, and you never know when you hit that threshold where something serious happens.

Well it's probably on both our sides of the misunderstanding.

But take an equal sized engine and measure the surface area of all the water jackets and the surface area of the air cooled engine and you will have less with water.

On a 1.6l VW engine even the cylinder liners are exposed to air, the heads have "heat sink" fins all over them, etc. Essentially every part of the engine that get's hot is exposed to air.

Now the water cooled engine can get away with less because of the thermal properties of water vs air.

But if the 747's brakes overheat it runs off the runway and potentially kills 400+ people.

On the LeMans example, none of the prototype cars and I'd bet the majority of the rest of the teams run drilled rotors (or cast rotors with holes in them, etc).

Well I'll go a step farther, whatever small benefit there may be with cross drilling is far outweighed by the negatives.

The difference is that this one can be proven without a doubt. It's just not easy for the "common" person to do it, and the magazines (like Turbo, SCC, etc) will never do it because they risk loosing ad money.

But even past that we know a few truths;
1. That the additional surface area by the holes being there is fairly small overall.
2. The reduction in mass from drilling the holes will raise the temps. (Again does the small increase in surface area make up the small reduction in mass?).

Here's the part where I think a lot of people get caught out, even I got caught the same way. When people buy drilled rotors, they also buy performance brake pads and most will probably flush and change fluid as well. So now that we have changed 2-3 things in the system, and they see improvements they love the rotors...oh and yea the pads to.

When I switched back from drilled rotors to solid rotors (but kept the better fluid and the performance pads) I noticed no difference in braking performance, no increase in fade (which I was having with the stock OE level setup). About the only thing I noticed a little different was maybe a little bit of the "bite" had gone away, but that may also psychological as well.

Manntis

Oy. I try to meet you with a Let's-Agree-To-Disagree and you press on with "No, I'm right".

Jaguar, who pioneered disc brakes on cars, sings the praises of drilled rotors as do thousands of well-respected automotive engineers and racers. I tend to take their side in this, you do not. Let's leave it at that.

JerkyBoy

Yea, and I'm the one with the attitude. You want to turn this into some philosophical debate like power vs handling or airbag issues, etc. Unfortunatly there is only one right and one wrong here. Hate to say it, either you're right or I'm right. There aren't 2 sides to it.

Again, show me the link from Jaguar that "sings the praises of drilled rotors". You keep talking about thousands of well-respected automotive engineers and racers who love them also. Name some top teams and top engineers who use them. You haven't yet.

You told me to call CART teams and tell them the bad parts of using drilled rotors and how they would laugh at me. Unfortunatly they don't use drilled rotors, and I wonder why that is. Why don't you call them up and tell them about these HUGE cooling benefits to drilling holes in their rotors.

You told me Brembo casts all rotors with holes in them, which is so far from the truth it's not even funny.

I showed you links/quotes from 2 highly respected braking manufactures who have much more "street credit" when it comes to braking systems than Jaguar does (nobody thinks of legendary Jaguar brakes....not like they do with Porsche), both of whom say what cross-drilled rotors were originally for and what they are for now (bLing yO!). Why would they say that? They charge more for cross drilled rotors, why wouldn't they tell us "Oh yea they are great, buy them".....hmmm let us ponder that for just a minute.

Hmmm chew on this a little bit;

There are many different reasons rotors are drilled or slotted. Sometimes the rotors are drilled to lighten them, though your weight savings is probably negligible. Honda claims the discontinuities help braking in the rain and provide an escape route for mud or rust. Fred Puhn's "Brake Handbook" says, "Some rotors have slots or holes machined into their contact surfaces. These reduce hot-gas and dust- particle buildup between pad and rotor. Although fade caused by gas buildup is less for a disc brake than for a drum brake, some fade still occurs. This is more prevalent with large brake pads, because the hot gas has a harder time escaping than with small pads. Therefore, slots or holes have greater effect in racing, where pads are large and temperatures are very high." Newcomb & Spurr's "Braking of Road Vehicles", 1967, tells us the mass of the rotor is the primary factor for preventing brake fade. When the rotor mass has absorbed enough heat, the brake will fade. Vented rotors and ducting schemes will cool the rotor faster, but it takes time; in rapid repeated braking cycles vented rotors do little better than solid ones. Carroll Smith's "Prepare To Win", 1975, says "Lately you may have seen discs with tangential slots milled in the friction surfaces or holes drilled in a tangential pattern normal to the friction surface. This is an effort to wipe the "fireband" or boundary layer off the disc before it reaches the point of contact with the pad and to provide the very hot particles of friction material worn off with some place to go other than the operating area."

Or how about;

DRILLED VS SLOTTED ROTORS

For many years most racing rotors were drilled. There were two reasons - the holes gave the "fireband" boundary layer of gasses and particulate matter someplace to go and the edges of the holes gave the pad a better "bite".

Unfortunately the drilled holes also reduced the thermal capacity of the discs and served as very effective "stress raisers" significantly decreasing disc life. Improvements in friction materials have pretty much made the drilled rotor a thing of the past in racing. Most racing rotors currently feature a series of tangential slots or channels that serve the same purpose without the attendant disadvantages.

http://www.stoptech.com/whitepapers/...ons_122701.htm (from a vendor no less)

Hmmm what do both of those say about mass? Anything in there about the increased surface area? There are some impressive names in there...very highly respected....but because it doesn't tell us how the Jaguar radiator in a 747 is cross drilled for cooling it probably won't matter.

And lastly you wanted to talk facts and physics, but instead of doing that you just call me argumentative and pressing on with the "No, I'm right" BS, but at least now you're not accusing me of being some other person, so maybe it's a step up. Or maybe it's because you can't find any real information that backs up your claims, as I said show me some respected information (and Sport Compact Car magazine is far from respected) that shows I'm wrong and I'll admit it 100%.

So do you want to talk facts and physics, or do you just want to whine about it?

Project84

I think they should make rotors the same size as the rims they are supposed to fit behind. Just one big massive friction area

On the real though, does anyone have a custom ram air duct going to their front brake rotors? I just read through all 4 pages of this slotted cross drilled rotor ****, and one person brought air ducts. Just wanted to know if anyone thought of doing it on a RX-7.

Directfreak

iTrader: (2)

Info on the CF ducts here Here

Project84

Thanks!

Maguire

iTrader: (1)

"Look at the guys that hot-rod their PC's, I can get a CPU fan that has a HUGE amount of surface area, and I can blow big super-fan on it.....yet a tiny little block of copper and run water through it will yield better results. " -jerky boy

I just want to say that i now am conviced that you dont know what your talking about. I know this is geting off topic. but, its relavent. i swear. Now im a computer nerd from way back when. Water cooling is a rather new technology. And where does the heated water go after it passes over the chips???? it goes to a electric radiator on the back of the case which then blows cooled !---AIR---! over the warm water. Oh yeah, and by the way, remember before they started putting fans on pc chips. What did the put on top of them? The put heat sinks with Really really really tall extensions. they worked really well to because they had greater surface area. Im not saying your wrong about this. But you are leaving out some very crutial points of your arguements.

Another thing i wanted to add. i dont know if anyone mentioned this or not because i didnt read all of these posts. But the reason reducing the mass of the brake rotor reduces so much weight from drilling out such a small amount of mass. Rotating innertial mass. get out your phyics book, its in there.

JerkyBoy

I'm talking about removing heat from the source (the CPU). A small water block will remove way more heat than a similar sized "air coooled" heat sink. Yes the water flows to a radiator, but on the air cooled side there are guys pumping hundreds/thousands of CFM of ambiant temp into their cases and still can't compete with a water cooled setup (ie they have WAY more capacity of moving air than the water cooled guys). The whole point was to get away from the freaking comparisons with radiators, since I have yet to see a water-cooled brake system yet, so any comparison between a water cooled/radiator system bears basically no real-world corelation to how your brakes work.

Maybe you should.

Huh? Yes and looking in your physics book what does that do to properties that will revolve around heat? Given a specific amount of time, and subjected to a specific amount of heat, which get's hotter the item with low mass or the item with high mass? Get out your physics book and look up the formula.

Yes, so are all of the rest of the principles which a few people don't understand about how this all works.

Manntis

I quote a brake manufacturer, you brush it off as manufacturer's propeganda. You quote a brake manufacturer, suddenly it's a "highly respected" source.

This is what I was referring to about there being a difference in philosophy on crossdrilled rotors - but you choose to continue with a "No, it's right or wrong" attitude and start back up again.

No, a few of us reminded you that crossdrilled are now typically cast that way, as manufacturing techniques have improved.

Right. Jaguar invented disc brakes for cars and the legendary D-types and E-types are still fondly remembered in European racing. Since then they've looked to maintain that part of their heratige on their high performance cars, just as Volvo strives to be the best at impact safety.

However, you say Porsche's are the brakes respected worldwide. Okay:

"The braking system is based around four-piston monobloc fixed calipers in lightweight aluminium with a distinctive red paint finish. These are combined with four internally vented and cross-drilled discs to deliver rapid and effortless braking response"

-Porsche Boxster S, From Porsche's own website.
http://www3.porsche.com/english/usa/...rs/default.htm

This car is no poseur, rated Automobile Magazine's Best Sports Car over $40,000, 2002: http://www.automobilemag.com/awards/...ers/index.html

And on the 911:


And the Turbo:


and on Porsche's technological showcase, where anything known to be pure fluff (or bling as you like to say) would be scoffed at by the automotive press, they include cross-drilled ceramic brakes



Porsche and Jaguar say crossdrilled brakes are for "bling yo"?? I don't recall seeing that line in their press releases. Oops. You didn't post a link to them saying so, and according to you anything without a link is BS.

If crossdrilled brakes were so widely renown for being a hoax with no benefit, as you assert, a small company with an image to protect like Porsche wouldn't add costly components to a safety system for "bling". We're not talking a Civic with aftermerket LED winshield washer sprayers.

Fred Puhn's book was last printed in 1985 and was based on information believed to be true in the late 70's. There have been significant advances in automotive engineering since then, including understanding several forces that were guessed at in Fred's day. Performance has come a long way since then - just look at 0-60 times for street legal cars. What was beneficial for outgassing and dust removal at the time was subsequently found to have an additional benefit; enhanced cooling.

Back to the ascerbic tone. Getting touchy because I finally got you to admit that surface area, not mass, provides cooling?

Definition of Cross Drilled Brakes from http://autorepair.about.com/library/.../bldef-101.htm

"Definition: Disc with friction surfaces which have been drilled with rows of holes to improve cooling, reduce weight and provide an escape route for dirt and gasses which can be wedged between the pads and disc."

I've not yet quoted SCC in this thread. I do read that magazine though, as do many on this forum, along with Road & Track, Automobile, and Car & Driver - and I enjoy all four.

Okay, here's some instruction in thermodynamic physics. The radiative cooling time for an object which remains at a uniform temperature with no limitation from heat transfer from the interior of the object is given by:



where k=Boltzmann's constant. In the real world, the surface will cool faster than the interior. The rate of heat transfer from the interior will be expected to limit the rate of radiative loss from the surface. By tapping into the interior (drilling or casting holes, f'rinstance) we greatly increase the cooling time. This is why baked pies hot out of the oven are often poked with toothpicks or forks, to allow the hot matter within to be exposed to air without having to first radiate through a crust, or barrier, of material.

Hence opening up the interior of the brake rotors to atmosphere, despite a relatively small decrease in volume of metal. This is an extension of the engineering rinciple of venting brakes, as was done on the GSL-SE and a large number of cars since. Automotive manufacturers are not known for generosity of manufacturing complexity, as seen by the Cavaliers with rear drum brakes still sold today.

I mentioned that radiators remove heat from hot engine coolant through a system using a high surface area for air cooling, you countered with "no one's invented a cross-drilled radiator yet" - In the radiatior illustration, the water/engine coolant is the matter being cooled, not the coolant itself, so stating that the point is moot as there are no water-cooled brakes is inaccurate. The comparison is air cooling the metal vanes of the rad, as air cools the metal of brake rotors.

Crossdrilling is the disc brake version of opening the core of heated matter to cooling air, just as a radiator is a lattice of vanes that separate the hot engine coolant and conduct it's heat into thin metal vanes (lacking the mass you've been claiming as superior to rapid cooling) so a greater surface area of thus heated metal is exposed to the cooling air and is assisted by convection governing, something next to impossible with a solid mass of metal.

While the physics behind the enhanced cooling and measured differences have been recorded by various manufacturers at as much as 200 degrees cooler for crossdrilled vs. solid rotors under sustained braking, there is a strong arguement that potential cracking, etc. offsets those gains. This is not the crux of your arguement, however. You jumped into this discussion by stating there were no cooling gains by crossdrilling, in fact there was a cooling loss as the mass of the rotor was decreased.

I resubmit that we're obviously both opinionated on this matter, as are several in the automotive community, and should agree to disagree.

Asking you to abstain from personal attacks which you have partially admitted were harsh is hardly whining; it's how we prefer things here in the 1st gen forum. If you get off on "yelling" at people online, mocking them based on little to no information of the background of the person you're addressing, may I suggest you try https://www.rx7club.com/forum/forumd...p?s=&forumid=9

JerkyBoy

Do you want to compare the difference between the company you mentioned and companies like Wilwood, Baer, Alcon?

I see, so both sides can be right then is what you are saying? Cross drilled rotors run hotter and cooler.

Ok, prove it. Brembo I believe does cast the rotors with the holes in them...on all their big brake kits. Of course this is a rotor that will cost you $200+ without the hat.

Just ignore the fact that Brembo (and probably every other company selling these things) doesn't even make the rotors they use for OE sized applications (which means they didn't cast it that way). They buy solid discs and drill them.

Show me a picture of a factory racing Jag from say 1990 to present with drilled rotors.

First, Porsche rotors aren't immune from cracking either. But again they are cast with holes in them. And second, again, show me a high end factory porsche race car with drilled rotors.

Essentially, there are huge difference's between a Porsche rotor and the OE sized rotor you will put on your RX-7.

I've highlight the important parts since this is the second time I'm quoting this.

Q: I don’t want to spend the money for a complete brake upgrade. Do you offer cross drilled rotors to work with my factory brakes?

Yes. Although there are some companies which sell cross-drilled rotors as an actual performance upgrade, in our extensive testing we have seen no improvement to be had by simply crossdrilling stock rotors. This is why Baer has developed EradiSpeed™ rotor upgrades for a variety of applications. Although it is true the crossdrilling, the slotting, or for that matter the zinc surface washing, are cosmetic enhancements, EradiSpeed™ rotor packages also feature rotors with thicker cheeks to provide more heat sink capacity in the fire path of the rotor. Also, they all feature directional vanes for greater pumping efficiency, as well as a two-piece design where the hat, or hub/hat section of the rotor is CNC machined from a solid billet of aluminum and is then fixed to the rotor ring using National Aviation Standard (NAS) stainless hardware. In other words, the EradiSpeed™ is much more than just the most visually appealing direct replacement rotor, it is the only upgrade of its type which can actually deliver the benefits of greater heat absorption, increased durability and lighter total weight.

In racing, crossdrilling was designed to alleviate a problem known as out-gassing. In some of the older pad compounds, when the pads reached elevated temperatures consistent with performance or racing use, the binder (that’s the material that holds the friction material in place) boiled off, producing a gas. This gas would build up between the rotor and the brake pad, effectively keeping the pad from directly contacting the rotor. The holes provide a relief path for these gasses, as do slots, so the pad can once again contact the rotor. Crossdrilling was NOT designed to facilitate cooling.

Although Baer offers crossdrilling as an option on their systems, it is offered as a cosmetic option only. However, with an EradiSpeed™ rotor upgrade, unlike a cosmetically altered stock replacement rotor, you will benefit from improved durability, greater heat sink capacity, lighter total weight and the visual excitement of a 2-piece, aluminum centered, crossdrilled, slotted and zinc washed appearance.

From http://www.baer.com/faq.shtm

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.

This from http://www.wilwood.com/faq.asp#question7

And;

DRILLED VS SLOTTED ROTORS

For many years most racing rotors were drilled. There were two reasons - the holes gave the "fireband" boundary layer of gasses and particulate matter someplace to go and the edges of the holes gave the pad a better "bite".

Unfortunately the drilled holes also reduced the thermal capacity of the discs and served as very effective "stress raisers" significantly decreasing disc life. Improvements in friction materials have pretty much made the drilled rotor a thing of the past in racing. Most racing rotors currently feature a series of tangential slots or channels that serve the same purpose without the attendant disadvantages.

This from http://www.stoptech.com/whitepapers/...ons_122701.htm

All from comapnies that know a few things about brakes.

Ummm, Porsche is a large company. And a large company needs to keep an image. Unfortunatly the common person doesn't know anything about high performance, but he see's holes in a rotor...and he knows it much be for cooling...and racing. I need those on my Porsche so I look like race car driver.

Mix that with the fact that the brakes on every Porsche are a few steps better than what is needed for a car it's size, and the expense that went to developing the brakes (back to casting the rotor with holes in it again), and then the fact that 95% of Porsche owners never drive the car anywhere near it's limits, it's pretty safe to say that they will have little to no problems.

Of course Porsche offers blank rotors as well for those that want to hit the PCA open track day.

Porsche doesn't even claim the drilled rotors are for cooling. Pay attention to the wording here;

Discs are cross-drilled to enhance braking in the wet. The brakes respond faster because the water vapour pressure that builds up during braking can be released more easily. The discs are internally vented for better heat dispersion.

Why don't they make the claim about the heat dispersion with the holes? But just the internal venting? Look at the marketing blurbs on the other cars and it's the same, they specifically don't say anything about the cooling properties of the drilled holes, but specifically mention the internal venting.

I read and enjoy them as well....but they are far from being a technical reference.

Ok, but what does the reduction in mass do to your whole mathmatical setup there?

It's not even mentioned, in fact you are saying that the temps between a solid disc and a x-drilled disc will be the same. Which they can't be.

What is the point of having a rotor that is capable of cooling faster, if it's hotter in the first place?

On your pie example, which will cool faster...the pie that is hotter but has 4% more holes in it...or the pie that is cooler but doesn't the additional holes in it? A hypothetical question since we don't have all the information, but maybe it helps illustrate the point.

If you lower the mass of the rotor by drilling a ton of holes in it, it will run hotter. Yes or no?

So even if it cools faster, it has more heat to get rid of. Yes or no?

What is the net result here?

Now add in the potential for the rotors cracking...and now what is the net result?

Where did these numbers come from?

Actually my first post talked all about the increased potential with having a drilled rotor. And the loss of thermal capabilities from the reduction of mass.

And thank you for getting back into the technical side.

jayroc

Whoa, bust out the blackboard, buddy...

I think I might get some x drilled/slotted drums for my 80...

Manntis

Porsche is a small car company, still family owned; It almost vanished in the early 90's with sales below 100,000 units worldwide. Compared to other car manufacturers they're a well known 'boutique' car.

Show you a high end factory Porsche with crossdrilled? I showed you a 911 Turbo and a GT with ceramics for crying out loud.

As to us both being right I'm trying to be diplomatic, not saying they're both hotter and cooler.

There are those who believe that crossdrilling keeps the brakes cooler. I agree with them and their evidence. There are those who do not, as you are one. I've stated this clearly several times now, yet you continue to oversimplify, ignore, and ridicule. Since you refuse to examine evidence presented, since you twist arguements presented to absurdity in your "summations", you have officially become a waste of time.

White84SE

Umm... okay.. let's throw another monkey wrench into the equation... I did see it mentioned that the "cross-drilling" causes high points of stress in the metals.. well, okay.. let's try cryogenically treating them.. I know racers who have had their brakes cryo'd on first-gen RX7's and it does prolong rotor life. Could this perhaps be the cure-all to the cracking problem? Or am I just an idiot?

--Danny

Project84

Yeah, I wanted to do the same thing, but I couldn't figure out if I wanted the run a CPU fan to cool the drum, or have it water cooled.

This thread is way out of control!

JerkyBoy

If you go back and carefully re-read what I said you will see the words...now pay attention here....show me a high end racing car with them.

Your answer to that is showing me street cars.

I oversimplified because, like above, you don't bother to read what I say or respond to it so maybe you are getting lost in it somewhere.

I ask you to show me a Porsche racing car with drilled rotors, you tell me all about street cars.

You tell me all about how Porsche has these rotors for cooling, yet Porsche themselves make no claim about cooling and it's for enhanced wet weather performance.

You try and "wow" us with your math, except the starting point of your equation is flawed....and nobody is certainly allowed to question what YOU say.

You tell us about these race engineers and race teams that all use drilled rotors.....but can't come up with a single one that competes in a higher level of racing.

You tell us how Jaguar loves them (but again doesn't use them where they are most needed on their race cars), yet almost every major brake manufacture says they are a cosmetic enhancement.

You want to move the conversation around by talking about 747's and radiators (which have nothing to do with cars or brakes and any moron can see that).

You get all hissy about my attitude, but your attitude is just as bad, except I'll tone it down and talk tech and then if I say something that may not align with your own little world or god forbid I disagree (and have something to back it up) with the world according to Manntis...I turn into a waste of time. I'm sorry that your ego is so fragile.

So if somebody wants to talk tech, let's go...otherwise we'll just let this thread die.

Manntis

Um... I said rotors were first used on aircraft because they have less mass, yet have superior stopping power to brakes. YOU brought up 747s. You also brought up CPUs and erroneously reported that they use mass, not cooling fins, to cool processors when the opposite is true (hint: open your computer and look - the faster the chip, the larger the slender air-cooling fins placed atop it)

You seem to miss the whole point of air cooling fins, so radiators were mentioned by myself and others in an effort to illustrate it to you.

Several of Porsche's "street cars" are raced as-is. I asserted that crossdrilled rotors were used for superior cooling on high performance cars. Period. No where did I say that they do not crack; no where did I say that they are not for high performance street cars but only for race-dedicated chassis; these are merely further illustrations of your "interpretations" of my posts.

My math is sound, a well-known equation to calculate radiated cooling from a given object, and is based on surface area and core temperatures. You distort it by putting words in my mouth, mentioning rotors of different sizes, etc. to turn arithmetic computation into "Fun With Figures" in an attempt to stay one step ahead of your dazzle. In fact you distort, deride, and deny facts presented in an effort to obfuscate anything that disproves your arguements.

You're new to this forum, whereas many others have seen me expediently admit errors where they are irrefutable. Figuratively rolling your eyes and braying about "The World According To Manntis" will not provoke me into the nonsensical arguement. My complaints of your tone were not 'hissy' but a statement of this forum's preferred method of discussion; if you truly are new here you'd do well to take such advise.

Bye now. Enjoy.

Redwood

JerkyBoy

As is? By whom? You'll find very few drilled rotors at LeMans, 24hrs Daytona, ALMS, etc.

Again, show me some top level racing teams using x-drilled rotors, which you claim all these race engineers go goo-goo over. No instead you tell me all about Porsche street cars.

Not arguing that at all, the math is sound.

[quote]You distort it by putting words in my mouth, mentioning rotors of different sizes, etc.

Ummm, I never said anything about different sizes in relation to your equation.

Just answer me this one simple question.

Take two rotors, both exactly the same size....yet one has a bunch of holes in it and the other doesn't - This means the one with the holes in it will have less mass, which one has reduced thermal capability. This is simple physics here, and is well within your scope.

Yes, I am the one who has not answered all of your questions of statements....I am the one who is distorting, deriding and denying facts.

Again, you tell me about all these highly respected manufactures (like Porsche) and race engineers (you gave NO names) that believe in x-drilled rotors.

I show you that Porsche says nothing about the cooling effects of cross drilled rotors and only mention them for increased wet weather performance. I show you 3 brake manufactures with tons of racing experience between them all that say x-drilled rotors are a "cosmetic only" enhancement. You want race engineers, I support my statements with quotes from people like Carroll Smith.

What do you give me back? A quote from Jaguar (who doesn't even use the rotors on their race cars). And a math equation (while the equation is correct) based on data that is wrong (the assumption that both rotors will be at the same exact temp).

So again, do you want to answer my couple simple questions? Or just whine about how I deny this and that or distort this and that, etc?

Acuspeed

Okay,

'nough with the bickering back and forth. If ya'll wanna' continue the bickering, take it to pm's or emails ...