jeremy

iTrader: (1)

oh yeah, drilling rotors is bad as the internal forces are allowed to do nasty things now thatyou are relieving them. a true cross-drilled is now cast so that its internal forces are more balanced and kept in check. i'll leave the mechanical dynamics explanation up to manntis since he likes to type more then me.

Manntis

hehe you jerk, Jeremy

MIKE-P-28

iTrader: (1)

LOL

jeremy

iTrader: (1)

thought i'd hand that off to you.

1st7heaven

Back when I was pitting for the Mazda IMSA team, the reason for the drilled rotors was keeping the pads clean and cooling.

That said, my boss has a 99 Miata and does track events with it. He put the drilled rotors on and had nothing but troubles. First, the pads were kept too clean.....as soon as he touched the brakes on the track they would want to lock up!!! Second, they did crack....very quickly!!!!

I would stay away from drilled rotors on our cars. I autocross and run stock rotors and HP pads.....work great!!!! Oh yah, I use standard....not cheap.... brake fluid, I have never had any problems. Remember though, I really dont use the brakes very long.... my total run is normally less than a minute.

my $.02

diabolical1

iTrader: (3)

well, from what i understand, the performance of a cross-drilled rotor depends a great deal on the way the rotor is made and drilled. i've heard many arguments, many glowing reports, and many horror stories. so my only word of caution would be to do research on the companies. unfortunately, Brembo and AP Racing do not readily cater to our cars, so we have to deal with KVR and Power Stop/Power Slot. the info i've found on them (in terms of history and methods is sketchy, at best) so we can either take the chance (being aware of the potential dangers) or just not buy them at all. cross-drilled rotors are generally a good thing in terms of braking performance. i think manntis covered everything that needs to be covered, so with that said, just try it.

peejay

The neat thing about cross drilled rotors is that the holes quickly fill with rust. Even if they are cad plated, the plating on the face wears away and rust can quickly de-laminate away the plating in the holes.

And then the rust gets in the pads and causes all manner of brake squeal and dust, and scores the face of the rotor...

But hey, on the plus side, at least crossdrilled rotors cost a lot more and reduce the amount of mass so that they heat up faster!

Manntis

here we go again...

JerkyBoy

At the expense of your own safety? Why not pick up some ultra-light weight magnesium wheels for normal street driving as well?

I've seen x-drilled rotors start to crack on street driven and only street driven cars. Some of them were cars that weren't driven anywhere near what one would normally called "hard".

Remember that driving on the street can be very hard on brakes. Especially for the "average" person (including the average enthusiast). I don't know of a single person who takes their car to the track and doesn't do a complete inspection of the brakes before hand. I also don't know a single person who goes to those lengths before hopping into the car to go to the corner store.

I'm sure the extra mass has nothing to do with the ability of the brakes to handle heat as well.

You may want to crack open a physics book again and recheck that theory.

In addition, cross-drilling helps to prevent warping, similar to the frost-holes in the floor of your car.

Metal expands when heated, and dramatically so with brakes. They go from being in a cool airsteam to friction-generated temperatures in the hundreds of degrees in a fraction of a second.

If the metal is a solid slab, it can warp. as central areas push on outer areas. Metal with holes in it, however, tend to expand more evenly as central areas are allowed pressure relief via expanding into the holes.

This dimensional stability issue is true of virtually any material, to varying degrees. Bridges have expansion joints running across them (that steady thump......thump.....thump you hear driving over a span) so constant heating/cooling can be relieved without cracking or warping the surface.[/quote]

I'm dumbfounded.

Yes, so let's drill a bunch of holes in the solid slab of steel, which reduces the rotors thermal capabilities (you cracked open the physics books right?)....what a brilliant idea!

Yes, call up Porsche....or any CART team...and ask tell them all about their drilled rotors....the person they will be laughing at won't be anybody but you.

You do know that CART teams, and Porsche and probably some of the other truly high end brake rotors out there use CAST holes...not drilled.

Search the net for a little while and come back and explain to us why we would want to DRILL into metal (just a hint, but on something like a brake rotor it's a bad idea).


Actually if you look at extreme endurance events like LeMans or 24hrs of Daytona you won't find many teams using x-drilled rotors (goes back to that reliability thing). Most of them will use solid rotors, or will have very few slots in them (3-4 slots seems common on the slotted versions). And the slots are cut quite different than they are on any "street" rotor I've ever seen. Now on other racing cars like CART, sometimes they do run drilled rotors, but they only drive an average of what 200 miles before throwing away their rotors?

Do you see a distinction between 200-500 miles in a race and the kind of mileage a street car will get?

Yep...See above.

Of course not, but if you think there are any similarities between the rotors you buy for $130 for your Mazda and any of the cars listed above then you are hugely mistaken (and no, I'm talking about more than looks here). And on top of that I know a few Porsche guys that go to PCA events fairly often and they pulled off their bLing-bLing x-drilled rotors because they started to see cracks forming at the holes....and swapped them for....solid rotors.

Directfreak

iTrader: (2)

Okay guys,

No more arguing over this please. I personally know the pros and cons of crossdrilled rotors.

As I said in the original start of the thread..

"I have made up my mind"

I wasn't asking about the pros and cons of them, or why I should or shouldn't get them. All I wanted was to find out the cheapest place to get them for the best price.

Thanks.

Manntis

They're cast with holes in them, but are CALLED crossdrilled, even on Porsches.

As to the physics of expansion/contraction of materials I stand by my original statement.

now cram your condescention. I wasn't flaming you, but correcting you in a reasonable manner.

peejay

We've taken the thread over, too bad

diabolical1

iTrader: (3)

well, it's always a point for debate. every rule has an exception, every argument has a counter ... blah, blah!

anyways, i'm with directfreak on this ... he made his decision, and it's his thread. i'm only curious as to why jerkyboy with 1 post, is so, seemingly, on the defensive when manntis' post was in response to someone else. am i missing something?

diabolical1

iTrader: (3)

i love an instigator! yesssss ... you go peejay!

jeremy

iTrader: (1)

you all are all wrong. brakes are useless as everyone should run race tires and have a suspension that can pull 45g's. :P:

cast cross-drilled rotors are used to dissipate heat better and clean pads. the redustion in mass (which isn't a really high percentage anyway) is offset by the surface area that is available now to release the heat. what if you're radiator had 20 rows but only 2 were exposed to airflow? besides, most upgrade to larger brakes when they buy those anyway. better lever arm, better weight, and better cooling effeciency. but as was said, cracking. this can be solved with duct tape however.

jerkyboy, we already said that drilling is bad and casting is good. the reason behind the races teams not using crossdrilled anymore is the invention of the carbonfiber rotor. expensive as #$%! but able to blow away an metal rotor. i'm dimbfounded, you have one post and its being a cocky smartass. you can tell a point without cutting on people. take off that mask so we may know you're identity. macho man randy savage?!?!?!

JerkyBoy

You are 100% sure on this? That $130 rotor is not drilled? The manufacture went to the expense of putting in the infrastructure to cast rotors for what is a very limited amount of sales. And can still keep the price down to $130? Suuuuuure.

Ok but let's pretend it's true....want to compare the other specs between a $250 Porsche rotor and the rotor you're going to buy for your RX-7? We won't go into size, we won't go into thickness, etc.

Uh huh. So what is the exact percentage of mass anyways? Since you know it's not a high percentage, what is the difference? I'll say it again here Xdrilled rotors don't aid in cooling.

What if the sky were green and the leaves were blue? I ask this because we're talking about brakes, not radiators.

What if I were to build liquid cooled brakes that had 20 rows, but only 2 were exposed to airflow?

Better weight? Almost every big brake upgrade I've ever seen has weighed more, especially the rotor. Maybe you know some way to make something larger out of the same material and have it weigh less. If so, there is this little prize they give away in Switzerland for great achievements.

Now if you want to upgrade to carbon rotors that is a different story.

That's good.

Ok, tell me why....and use science not just "ummm, cause they are" to back up your statements.

The problem is that somebody came in here asking a question, and he's given WRONG advice based on BS tech that is THOUGHT to be right. When you see a race car with drilled rotor it does ZERO for cooling (most race teams run much smaller brake ducts than is needed, hence they are getting plenty of cooling), and it isn't there to cure "warping" (race cars change rotors every race...so why worry about warping).

Here's what Willwood says about x-drilled and slotted rotors;

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.

Hmmm how about Baer? What do they have to say?

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.

So to be put simply, cross-drilled rotors are bad. They are a gimick...not much different than light up washer nozzles or led's in the tailpipe.

I'd bet ya that if you took the same car, with the same pads with the same brake fluid, etc....except one solid rotors and the other had cross-drilled, the car with solid rotors will stop more consistantly with less fade than the car with the bLing-bLing rotors.

SilverRocket

Directfreak, I guess everyone is just wondering why you want to spend extra on something that seems kinda worthless (other than to impress ricers)...

All I know is my car (with stock rotors, hawk HP+ pads and Motul 600 fluid) stops harder than my 205 Toyos can handle; I can lock them up at pretty much any rate of speed. I can't imagine needing anything more on the street or autocross; in fact, what would make the most difference would be a stickier set of tires.

What tires are you running that you need more braking power? I'm guessing you aren't able to lock them up?

My car is also very light; maybe that has a lot to do with my opinions.

Oh, and I have *never* been able to fade my brakes on the street, despite my concerted efforts lol. I think it would really take a racetrack to see any weakness in those Hawks.

diabolical1

iTrader: (3)

Quote:

So to be put simply, cross-drilled rotors are bad. They are a gimick...not much different than light up washer nozzles or led's in the tailpipe.

SPLASH!!!!! Okay, you've made your mark.

Dude, I really don't recall anyone saying that they were necessary or even "good" for the street, so you've pretty much crossed over from giving tech advice to chastizing (sp?) everyone in your infinite knowledge.

Look, Directfreak, himself, said that he didn't care about the technical crap ... he MADE his decision to get them. Case closed! No more argument! Now Manntis posted what he knew, and you've posted your rebuttal ... but the "voice of Muhammed from Mecca" tone is uncalled for ... just agree to disagree and call it frickin' day.

Look, I don't think most of know (or even care) about the physcial theory behind thermal dynamics, heat dissipation, metallurgy, etc.

I'm not flamin', I'm not trying to discredit what you said, I'm not agreeing or disagreeing, all I'm saying is calm down. It's not that serious to blow a seal over.

peace,
d1
nuff said ...

jeremy

iTrader: (1)

i'm blowing a seal though. jerkyjerky is obviously going to be an *** so here we go. i'll have fun untill they lock the thread and directfreak doesn't care since he has the info he needs. thanks for the answer and yes i stand corrected that the surface area is not as beneficial as i thought. however surface area is important to cooling more so then simply mass. that is basic thermal dynamics. the amount of material exposed will allow a better transfer. i used the radiator as an example of mass vs surface area. it was a relative statement to back up my point. maybe if your head wasn't up your almighty alter of an ***, you would figure that out. i also know that most brake upgrades way about the same or maybe less due to aluminum hats on many kits. so part is out of a different material switzerland achievement ***. just thumb through a few scc mags and look at there weight comparisons vs stock. and why should i tell you how carbon fiber brakes work better since you know everything anyway. maybe i'm not writing a damn paper here, just tidbits of info i know. just because someone says something that you don't feel is right doesn't mean we want to hear you rant and rave like a expert know it all. bLing bLing.

JerkyBoy

Far from infinite knowledge....but when I do see a topic or a question I keep my thoughts to myself unless I do know something about the subject, and then I make sure I have my facts straight just to be sure.

Not go on and on like some others here that have not done a single bit of research into the subject and keep going on and on with what they think is right.

Fine, all I ask is that people do their own research. Research involves actually looking at a book, reading material from real experts in the field. Not just applying high school theory to complex problems, and then assert how correct they are.

Really? Do you care about how your engine runs? Do you care about how your car stops? We're all enthusiasts, but what seperates the posers and ricers from the real deal is knowledge. If you don't want to do at least basic research into the "problems" that come along when you modify your car, you will never have a well sort out car.

I am calm, I'm only offering an opinion backed up by facts. What I get for that is not a real "rebutal", but more "street" tech backed up with no facts or science.

Well at least we're learning.

I see...so maybe we aren't learning. Hate to tell you this but a tiny *** rotor is not going to cool off if it doesn't have mass. We're talking about brakes here, where temps can rise to over 1,000F....the little bit of surface area that is there is going to do very little for getting rid of that heat.

Of course it will. However holes in the rotor does nothing for cooling, so what is the point?

But hmmm, what about those Formula 1 guys...what do they do? F1 limits wheel size to 13", which means they are probably running maybe 11" brake rotors (that's smaller than you will find on many, many cars these days). Yet they have no problem stopping these cars from 200+ mph speeds down to double digits lap after lap for a couple hours. How do they do that with so little surface area?

It was a bad example as it has little to do with how your brakes get rid of heat.

No..no, I got the example, it was just damn stupid.

Well Car and Driver did a little test with a WRX and 4 big brake kits. 2 of the kits had lighter rotors, 2 had heavier rotors. It was about +/- a pound or so. The calipers is where the bigger weight savings are, but that's not going to make a huge difference since it doesn't rotate.

Huh?

[quote]and why should i tell you how carbon fiber brakes work better since you know everything anyway.[quote]

Well it's amazing the grasp you have now, I figured you could enlighten us all on why carbon brakes are better.

Tidbits is about right.

Again, it's not what I feel is right, it's backed up by people who actually know something about the subject. Understand the difference? You have yet to explain any of your "theories" beyond something you did read in Sport Compact Car (such a well reknown technical magazine).

Anyways, the original poster made his choice, and he'll probably never have a problem with them....or he could be running down the highway one day and need to slam on the brakes and he'll get to find out what a broken rotor does for braking performance.

I'll drop out of this thread then, since I've made my point long ago, and it's nothing more than **** slinging now....that and this;

Has gone way off the meter.

Directfreak

iTrader: (2)

Excellent points made by everyone.

Now let's get along.

The car will be driven less than 4 hours a week, and babied around. It is NOT a daily driver, and not a "road track" car. The most action it will get will be at the 1/4 mile strip.

Yes it is purely for the bling-bling factor. I am going to get wide wheels where you can see the rotors, and I want the cadmium plated, cross-drilled rotors to be visible for all to see.

Bling-Bling? Yes.
Ricer? Maybe.
Informed on the pros and cons? Yes, especially now.

My Choice? Definately.

I will still rate this thread 5 stars, despite the petty arguements, & based on the good overall info.

Manntis

Gee, I guess being head of the team that modified the brakes on the LSVW to correct problems with the asbestos pads & solid rotors, and having worked as a mechanical engineer for years, means that my experience is just "posting what everyone thinks to be true" whereas a brand new identity created to refute me should be taken as gospel.

No need for name calling or personal attacks; let's stick to facts and physics. One of your key points is that cross-drilled do nothing to cool the brakes. There are those that disagree:

"Directionally cross-drilled for enhanced cooling" - Jaguar

"Question- Why should I use cross drilled rotors?

Answer- The primary reason is that they run cooler, approximately 200-250 degrees cooler when used with high quality pads. This reduces the chances of warping, which has become a major problem in recent years, particularly on late model U.S. made vehicles."

-Power Stop, brake rotor manufacturer

mar3

iTrader: (8)

You know what's really funny? Who, in this long and sometimes snoozing thread has actually got cross-drilled brakes on a street car, right now? Who has actually run cross-driiled rotors on a street car for more than a month? If you haven't, shut up already with other people's experiences or crap that you have read. This is the truth. I ran cross-drilled rotors for 2 1/2 + years on my '80. I bought the rotors new from Mazdatrix and had a local machinesmith drill the holes based on my pattern and his experience for the actual hole size. They never developed the dreaded cracks that everyone thinks must happen every time you put C/D rotors on the street...period As far as I'm concerned, that is a myth that has been made a truth because it has been repeated so many times by people that never tried to run them on the street. Probably one guy somewhere in the distant past had it happen to him and the story has blown up into an urban legend now concerning cross-drilled rotors. The only thing I didn't like about them was the astronomical rate at which they ate up pads and the constant dusting always on the Weds. Yearly pad changes were the norm and this car never saw track duty except for the drag race day prior to it being totaled...

JerkyBoy

I'm new to the board, not just making up a name to refute you or hiding behind some name or whatever else you want to think.

Ok, let's.

I'm sure there are lots that disagree. But when we go back to look at facts and physics it will be fairly easy to understand why a cross-drilled rotor is a bad idea for performance.

Please list the source of this information, where I can go to find all of the information...all of the facts as you would say.

See above 2 posts from Willwood and Baer, both of whom have WAY more experience in building high performance brake systems than a company that drills rotors.

Let's go a little further into that though. First of all warping has been a problem in the past, newer cars are quite a bit better in that regards. On the subject of surface area being there to reduce heat, drilling holes will add maybe 4% to the surface area of the rotor.

Here is a little information from somebody on another post on another forum about this same exact subject.

He is listing the most important functions of the rotor;

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle

#2 DISSIPATE the heat

#3 REMOVE the heat from the brake system

Let's look more in-depth at each step now shall we?

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle:
This one is pretty simple and self-explanatory. The rotor's surface is where the pads contact and generate friction to slow the vehicle down. Since it is this friction that causes the conversion of forward acceleration into deceleration (negative acceleration if you want) you ideally want as much as possible right? The more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping.

#2 DISSIPATE The Heat:
Let's assume for a second that the vehicle in question is running with Hawk Blue pads on it. The brand doesn't really matter but that is what I am using as my example. They have an operating range of 400 degrees to 1100 degrees. Once they exceed that 1100 degree mark they fade from overheating. The pad material gets too soft to work effectively - glazing occurs. This means that a layer of crude glass forms on the surface of the pad. As we all know glass is very smooth and very hard. It doesn't have a very high coefficient of friction. This is bad - especially when I am coming down the back straight at VIR at 125MPH. Lucky for us the rotor has a job to do here as well. The rotor, by way of thermal tranfer DISSIPATES the heat throughout itself. This DISSIPATION lessens the amount of heat at the contact area because it is diluted throughout the whole rotor. The bigger the rotor the better here as well. The more metal it has the more metal the heat can be diluted into.

#3 REMOVE the heat from the brake system:
This is the step where the rotor takes the heat it DISSIPATED from the pads and gets rid of it for good. How does it do this? By radiating it to the surface - either the faces or inside the veins. It is here where cool air interacts with the hot metal to cool it off and remove the heat. Once again there is a reoccuring theme of "the bigger the better" here. The bigger the rotor, the more surface area it will have which means more contact with the cooling air surrounding it.

Now let's look at why cross-drilling is a bad idea.

First - as we have already established, cross-drilling was never done to aid in cooling. Its purpose was to remove the worn away pad material so that the surfaces remained clean. As we all know this doesn't have much of a purpose nowadays.

Next - In terms of cooling: Yes - x-drilling does create more areas for air to go through but remember - this is step 3 on the list of tasks. Let's look at how this affects steps 1 and 2. The drilling of the rotor removes material from the unit. This removal means less surface area for generating surface friction as well as less material to accept the DISSIPATED heat that was generated by the friction. Now because of this I want to optimize step one and 2 since those are the immediate needs. If it takes longer for the rotor to get rid of the heat it is ok. You will have a straight at some point where you can rest the brakes and let your cooling ducts do their job. My PRIMARY concern is making sure that my car slows down at the end of the straight. This means that the rotor needs to have as much surface as possible to generate as much friction as possible and it needs to DISSIPATE the resulting heat AWAY from the pads as quick as possible so they continue to work. In both cases x-drilling does nothing to help the cause.

Now let's talk about strength - and how x-drilled rotors lack it. This one is simple. Explain again just how drilling away material/structure from a CAST product DOES NOT weaken it? Since you are obviously a man of great knowledge and experience surely you have seen what can happen to a x-drilled rotor on track right? Yes it can happen to a non-drilled rotor as well but the odds are in your favor when pimpin' bling-bling drilled y0! Since you are also an expert on thermodynamics why not explain to the group what happens to a cast iron molecule when it is overheated. I will give you a little hint - the covalence bonds weaken. These bonds are what hold the molecules together boys and girls. You do the math - it adds up to fractures.

That basically sums it up, or maybe there is something wrong in there, but if there is bring some real facts and physics to the table to refute it.

Want to read some more opinions from one race team?

http://www.teamscr.com/rotors.htm

I had them on a car for about 2 years or so.

That's nice. After 2 years on my setup, I had spider cracks on almost every hole. Given some more time, those cracks would have gotten much more serious, which would have led to some type of really bad things happening.

On a regular solid disc over that same amount of time (and longer), no cracks, no problems.

Out of all the brake rotor failures I've seen personally, I'd say about 80% of them came from x-drilled rotors. That's "catastrophic" level failures. In terms of rotors I've seen on cars, I always see small cracks around the drilled holes on x-drilled rotors after a period of time.

So I'd say it's more than just an "urban legend" as you would say, but it's still far from a large sample rate to get truly meaningful data from. But if you start to dig a little deeper and just do some rudimentary searches on Yahoo or Google you will find lots of people experiencing cracked cross drilled rotors, on all kinds of different cars (from light weight to heavy weights).

And I'll leave with you this;

Manntis

That's a slotted rotor, not cross drilled. Don't use pics of apples when arguing about the structure of oranges.

I find it highly unlikely that a new member would join, then jump right in with a confrontational tone in his new post; especially when it coincides with recent incidences with trolls and unseemly PMs.

If you are a genuinely new member, learn to tone it down; we're all here to exchange info. If it's fights you're looking for I'm sure there are several other forums that would be happy to oblige you.