Sterling

You're all ********! Everyone knows you'll **** up the compression ratio if you drill holes in yer rotors.
Gueeze!

Sterling

Hey...Wondering what the pro bike guys have to say about this. Every superbike I've seen has cross drilled rotors, at least a giant one up front.
If they were that prone to cracking, would'nt just the thought of that about make you **** yerself everytime you got on yer bike?

Hyper4mance2k

iTrader: (40)

nice point about the super bike thing, but they are only cross drilled with no vents. Also a bike and rider will allways weigh less then 1000 pounds so those breaks do alot less work. And cross drilled will work better then vented (in that situation) because vents cool much more and would keep the breaks really cold and be even more prone to crack cause of the extreame temprature changes when braking force is applied.... NASCAR cars weight in the neighborhood of 3500 lbs and they ALL use vented rotars to slow their cars down from 200+ MPH all day long this was actually a sublect on nascar tech recently thay said that cross drilles and slotted altough great in theory aren't practical for any reason except for maybe rally and F1 racing where the car is under serious breaking for hours and hours at very high speeds so if you plan on racing your car in a class where you would be pushing it for more than 3 hours straight then you'd might consider x drilled or sloted but other wise not worth the money

JerkyBoy

I see, so you are saying the act of putting a thin slit in a rotor will do less to weaken it than drilling tons of holes in it?

If you like, you can find tons of pictures of cracked drilled rotors on the net if you don't believe.

Think what you like, but it's still true.

Since you are an older member maybe you should learn that maybe what you are saying is wrong, I'd even go so far as that as a senior member newbies will think that what you say is more likely to be true than somebody else. So what that means is that be damn sure what you are saying is correct.

My last post had no name calling and very minimal attitude compared to your posts, yet you wanted to "Argue" about facts and physics, yet you haven't laid out one piece of it...so where is it? Let's talk tech and get to the bottom of this for the benefit of everybody in this forum.

It goes even deepre than that. As you mentioned the weight is the reason for the brakes the way they are. If you look at the size of the discs compared to the weight of the bike and rider. They cross drill the rotor solely for weight savings, not for any kind of cooling.

This is also why you see people throw on those fancy "wave" rotors and such, a bike typically has way more brakes than it needs.

Well as pointed out Nascar doesn't cross drill, neither does F1 (http://www.f1mech.co.uk/brakes.htm is a good link that has some good pics). Nascar is a great example because there are places where they have to bring those big heavy cars down from speed, yet they don't use anything more than a slotted rotor.

Manntis

This is the confrontational tone I'm referring to. Tone it down or go elsewhere. Your syntax and zealousness sounds very much like another individual who was recently examined by mods for banishment for PM harassment; and the fact that you suddenly appear and seem adamant on attacking a point made by me using the same writing style is suspicious to say the least.

if you want to stay, or at least stay and be respected by other forum members, keep it to info not flames.

As to being sure I'm correct, do a search online and you'll find hundreds of sites stating that the purpose of cross-drilling rotors is cooling, not weight savings. I even quoted Jaguar, the first car company to use disc brakes on cars, in a previous post to which you responded "why not provide sources" although I cited Jaguar as the source.

Now just relax. As you'll notice there is occasionally contradictory information posted in here; that's why it's called a FORUM, as in a place where things are discussed. There have been occasions where I've been in error, and when accurately corrected I am among the first to acknowledge my error. This, however, is not one of them.

This is where your logic is inversed. The bikes are already light; the few grams of weight saved by crossdrilling would be next to pointless. Again, do a search. Automotive engineers in general agree that there are cooling advantages to increasing the surface area of exposed metal via crossdrilling.

An increase in metal mass does not allow more rapid cooling if that mass is inside the rotor, not exposed to air. This is why air-cooled engines have cooling fins; to increase the surface area of metal exposed to atmosphere.

Sterling

Directfreak, you sure do know how to start a ****** thread, man!

Directfreak

iTrader: (2)

I feel like Jerry Springer.

syklone

you'd save more weight by taking a **** before your run then by cross drilling your roters.

JerkyBoy

Fine, you PM the mods and ask them to compare IP address's (hell even the subnets), email address's whatever else, then they can tell you that I am not this person.

I have quoted info, you haven't. You wanted to talk about "facts and physics", you have come up with zero. You haven't backed up any claim you have made with anything other than a one line quote about Jaguar, which you didn't even give us a link so we can read the whole thing in context.

I have done a search. Everybody with even a little bit of expertise in the area has said the same thing. Cross drilled is not for cooling, and in todays age is only for looks.

So what are you searching on? Post some links to some reputable sources (the more the better) that talk about how cross drilling is for cooling and that there is no detrimental effects (like cracking rotors) to doing it, oh and make sure it's not a "sales" ad as well. The information is out there.

Prove it. Give us some links to some information that proves you are correct, information that is consistant in many places and isn't marketing lingo. When you come up with that, I will say I'm wrong and you are 100% correct.

Really? Spoken like somebody who has never even researched about what a race team does to get ready for a race. A few grams here and a few grams there tend to add up to a few pounds here and a few pounds there. Do you really believe that these guys will not go to extreme lengths to remove a "few grams"?

Of course there is huge benefits of increasing surface area. However drilling and weakening a rotor to gain maybe 4% increase is a very silly way to do it. Especially given the fact that you can add some brake ducts and run much lower temps than the 4% increase will give you.

No but it will allow the piece to absorb more heat. And more importantly pull the heat away from the areas that are most effected by it (the calipers which hold the pads and brake fluid).

Why do welders attach things to items they are welding sometimes? To use as a heatsink, right? They are adding mass to what they are welding to lower the overall temps. Kinda-sorta the same thing with brakes. Or do you disagree, and why?

syklone

But the mass they are adding also adds surface area.

JerkyBoy

Of course, but before you can get the cooling effects from surface area, first the mass has to absorb the heat. So if you reduce mass the piece will get hotter.

The big question is does the sub 4% addition in surface area make up for the loss of mass? Or will it be a wash? Or will it make things worse? And asking those questions doesn't take into effect the weakening of the rotor by drilling a bunch of holes in it, or the stress you create by doing the drilling into a cast piece.

Essentially, by looking at what the "pros" do will tell you the truth. If drilling holes in a rotor were the smart way of cooling a brake rotor, they would be doing it. But the vast majority of upper level racing teams will not touch cross drilled rotors. Ferrari spent probably billions of dollars on making the brakes better on their F1 cars over the years, any holes in the rotors? Nope. Porsche has probably spent similiar amounts. Any holes in the rotors of their top level race cars? Nope. Both of these companies would do it in a heart beat if they thought there was some competitive advantage to it. Nevermind the vast majority of ALMS, NASCAR, IRL, CART, F1, etc racing series.

Sterling

YEEEEEEEEEEEEEEEEEEEEEEEEHAAAAAAAAA!!!

jeremy

iTrader: (1)

well i'm glad to see you are learning. as i said and you rebutted me, there is more to heat control then simply mass. i DID NOT say mass was unimportant. however, if cooling is increased by increasing surface area then less mass is needed to absorb heat. it matters not if you can absorb a ton of heat but can't rid the system of it so it builds and eventually heat soaks. thats like arguing that vented rotors are stupid due to decreasing mass. and the mass doesn't first have to absorb heat. if you can bleed the heat off as fast as it created then that works. that would be called engineering. finding the optimal surface area vs mass to fix brake fade etc due to heat soak.

the biggest problem with crossdrilling is the needed ducting to funnel air perpendicular to the rotor so you get good flow through it. otherwise the air will have difficulty making that 90 degree turn but this doesn't necessarily mean you won't see an improvement. maybe it just isn't enough of an improvement for the supposed side affects. manntis has been quoting places of knowlege etc just like you. also most newer cast rotors have a radius or chamfer around the holes as to not build up concentrated stress there while heating and cooling as this is the main cause of the cracking.

you'd save more weight by taking a **** before your run then by cross drilling your rotors. - thats just funny as ****.

and as for my example being damn stupid. a radiator is accomplishing the same thing we are talking about with brakes at the moment, the ability to absorb and shed heat. most people know about three row radiators, etc, and can relate to why they work better. mass and surface are. its based on the same thermal dynamic principles. oh yeah, slotted rotors were based on a different set of ideas and are different geometrically as well as how the handle air flow. the apples/oranges thing is well said and i guess i could give you the damn bad example bullshit on it. now what smart *** remark will you give me now? i know there is something i said that you can make fun of and call me ignorant and stupid over. i'm just highly impressed with those quoting skills. are you originally from a debate forum? the structuring poise and grace to single out each comment or rebuttal and set it up into a flowing arrangement.

JerkyBoy

Well, others have eluded to that very thing, that mass is not at all important, surface area is. They are both needed.

But the problem here is that we are upgrading the rotors for the purpose of reducing fade. To reduce fade we have to lower temps, or put something in place that will take higher temps. You'll never be able to bleed the heat off fast enough in a braking system in most applications. So we can upgrade the rotors to cross drilled, however by doing this we are only adding maybe a 4% increase in surface area to the rotor but we are also lowering it's mass. Therefore because it lost mass it's going to get hotter, the big question is how much hotter and will the 4% increase in surface area compensate for it.

Then we come to the place where drilling and removing material from something as important as a brake rotor is not a good idea. As you are weakening the rotor, and if there is one part on a car that I never want to fail brake rotors are very high up on the list.

That goes back to one of my earlier posts, look at what the top engineers do exactly in this situation. Do the top race teams use them? The answer is mostly no, they do not. They use the biggest rotors they can manage in the rules, then sacrifice aerodynamics by putting brake ducts on the car. This tells us a lot right here about what they are thinking. They are willing to sacrifice speed on their race car (it may only be 1-4mph, but they are spending millions to get .001 second a lap) to get cooling on their brakes. If cross drilled rotors worked so well for this, or even gave a 5% reduction (meaning they could close those brake ducts just a little more and go a little faster) they would be doing it. Even short distance racing, sprint racing (open track events of like 30 minutes) the teams stay away from them.

And those guys drive only a few hundred miles at most, on the street people will put 20-30 thousand miles on a set of rotors, without really inspecting them that often.

Chamfering does indeed help, but does not reduce the problem. Drilling holes in the rotor is just not a good idea for longevity.

I've even seen Porsche 911 rotors with cracks in them, and they are cast with the holes in them (no drilling into it to create heat risers, etc), and this is a company that is famous for brakes. Granted that is rare, but it does happen.

Depending on the rules structure of whatever racing series you are looking at, you would laugh your *** off at the amount of crap they do to drop weight.

Maybe a little harsh...

But the radiator isn't a high mass piece of cast iron to absorb the heat. The engine pumps water through it so the fan (or the air moving across the fins as the car moves) can cool the water inside.

But less emphasis on mass. Again take a que from the high performance/racing side. To have lower water temps from the radiator you make the radiator bigger, but you can also make it lighter out of aluminum (hell some new cars come with half-plastic radiators), they aren't relying on the mass of the radiator to do the cooling.

But that was a picture of what happens when you stress a piece of cast iron rotor. It will crack where you were messing around with it. The same thing happens to drilled rotors (but since you have WAY more holes in it, you could end up with a lot more cracks, or a much weaker rotor).

You want to know the quickest way to improve the performance of your brakes? New pads that have a heat range that your "performance" driving takes it to, and fluid that does the same. Rotors don't fade they just get hot, the pads do fade when the rotors get to hot and the fluid does as well. Fix the problem, not put on a bandaid....drill a bunch of holes in one of the most important safety devices on your car.

diabolical1

iTrader: (3)

just an observation here ... and this goes back to my saying some of these issues and points of debate are based in the person/company and their methods.

i've got cross-drilled rear rotors (i ran slotted up front because of this same "cracking-phobia" that i got before i did my own research ) on my MR2 and i noticed something ... the width of the rotors are the same, as are the vanes that vent them. BTW, mine are the PowerSlot/PowerStop stuff and they have not cracked in the 3 years that i've had them, and they've driven across the country twice now ...
but regardless of their integrity, they still would lead me to believe that these are just made for the ... ahem ... "bling-bling"-crowd, not racers!

so i agree with what you said ... to some point

however, in the high-end cross-drilled rotors (like Brembo and AP Racing) when they make a brake kit, you immediately notice that the rotor are significantly thicker than the ones they replace, and that they also supply you larger calipers with them. a friend of mine has them on his M5 (E34), and to my knowledge, they have not cracked yet (and they have been on for about 4.5 years now)

so all i'm saying is that a lot of your points do have merit, but they cannot be applied GENERALLY, because there's always a set of conditions that will make something work.

and by the way, i just want to make sure that i give credit where it's due ... your last post was a LOT more friendly in it's tone than the ones that preceded it. speaking for myself, though i'm not part of the debate, that was what got me a bit miffed.

JerkyBoy

Good point, in the first case (which I didn't quote, but about OEM sized replacements) obviously the rotor can't change dimensions or else it wouldn't be a direct fit replacement.

This is where some of the problems arise, when you buy a stock sized Brembo for a "cheaper" car (something other than a Viper, Ferrari, Porsche, etc) it will be drilled. In fact I would bet dollars to donuts that Brembo had no hand in making the rotor, look at how much it would cost them. Imagine how many different sized rotors are out there, every manufacture probably uses a different combination of width, hub size, hole pattern, disc size, etc, etc. Sure there may be a few that you can cross reference, but I bet that number would be limited. So how would Brembo be able to cast all of these different sizes, then drill holes in them, then CAD plate it...and then turn around and sell them so cheap? An OE rotor from your local auto parts store may sell for what $80 or so, while the cross drilled counter-part sells for $130, that's not much of a price increase for a low demand item.

When it comes to the big brake kits, you'll see that all of them use some combination of the same rotor. The same 13.1" rotor used on the Suburu WRX kit will be the same one used on a Camaro kit that is also used on the Viper kit, etc. Ditto for calipers. Now compare the prices on the parts.

So I agree, the chances of problems on the big high end rotors would be less. But the problem is still there, as I mentioned I've seen Porsche rotors developing cracks, and they are probably pretty close to the ultimate in brake systems...at least on the street.

jeremy

iTrader: (1)

i agree, much more toned down thank you. the mass of the radiator is the water. adding a 3rd row means that the radiator now holds more water or mass as well as opening up more surface area. but enough about radiators. most people who are buying cross-cast-drilled rotors aren't looking for longevity, at least i wouldn't. typically, as you said, you upgrade your pads. with that comes more wear and thus more heat, meaning you are going to eat rotors much quicker. most race teams used to use crossdrilled rotors with the dedicated venting i mentioned to flow air through the holes at speed. however due to the lighteness, etc of carbon brake rotors, they don't use them anymore. but i'm not sure how many people here could afford that technology. now, if i can jam the 911 gt2 ceramic brakes in my wheels..............

Directfreak

iTrader: (2)

So where can I get Brembos or Wildwoods for a 1st Gen?

diabolical1

iTrader: (3)

no need to bet ... you'd clean up!
when i bought the brakes for my MR2, i was told that Brembo was involved with making the rotors, blah, blah, blah ...
it took a while, but i found out they weren't! i also recently found out that it seemed to be a selling point for some of the lower-end brake parts companies ... you know, to mention some sort of association with Brembo that doesn't cross any legal lines ...
well, there's an article in the September 2002 issue of european car where a rep from Brembo touches on that issue and basically (to paraphrase) he said that if you don't the Brembo logo from now on, then don't even bother to question affiliation with them.
not being a smartass here, but is that wildwood or wilwood - not sure, with all these pretender around here.

try -> www.wilwood.com (maybe e-mail them or something, i didn't see any ready-made stuff for the Rx-7.
about Brembo ... well, i had a few discussions about brakes and the Rx-7 in either 1998 or 99, and if i recall, they didn't seem that interested in helping to get something together ... i guess they could smell the "poorness" on my end ... hehehe - but hey, 3 to 4 years has passed since then, so maybe you could give them a try anyway.

JerkyBoy

But adding a 3rd row doesn't increase the surface area as much as it does the "mass" (in this case the water it holds). At least on percentage terms.

Well the differnce in longevity between a race car and a street car are different. On a race car replacing rotors before every race or every other race, which is certainly well under 1,000 miles is different than what you would do on the street. The inspection is also different, for instance when was the last time you inspect the side of your brake rotor that you can't see through the wheel? People who race even at amateur levels inspect that stuff top to bottom.

Of course there is a difference in the "abuse" brakes take as well, obviously on the track they will get used much harder, but that is a very controlled situation. Between a session when you do a quick look at your brakes and notice a problem, you don't race no more. When was the last time any of us did a quick inspection of our brakes coming out of 7-11? Also if you experience a small problem on the track (maybe the brakes start to fade a bit while out there.) you can slow down get off line and limp back to the pits, or maybe you run off a corner (most corners have a bit of run off room) so no harm done. On the highway if your brakes fade like that, say you are cruising along at 80mph and some idiot cuts in front of you at 40mph, or traffic is stopping or stopped, etc....if your brakes fade the chances of some type of accident are higher.

Yep, the price you pay to stop faster.

Well if there were benefits (that outweighed the negatives) of having holes in the carbon rotors those teams would use them. Even the teams that can't afford carbon rotors don't use the drilled rotors. They were used (as mentioned by the Baer FAQ) when pads weren't as good as they were today.

Bigger wheels and then start sending emails to these guys at http://www.ultimategarage.com/bigbrake1.html who made their name by adapting Porsche brake systems (rotors/calipers) to other cars. And then did it at prices that were better than similiar sized/spec'd kits from Brembo, etc.

Directfreak

iTrader: (2)

Oops.

Hey Diabolical,

What do you think about these?

Manntis

Thank you for rethinking your tone; however you're still overlooking increased cooling via surface area. If tri-cored radiators were all about increased mass (at this point it's no longer a heat sink, but a heated substance to be cooled) why have vanes in the radiator at all? Why not a lump of metal with coolant running through it?

Why do the air/oil coolers work better than the (water/oil coolers in these cars?

Answer: Cool air flowing over the heated surfaces having better cooling capabilities.

There ARE cases in which increased mass provides cooling, however the properties of such are finite. A good example is the radiator/coolant now being discussed. Water in the engine absorbs heat faster than air flowing outside the engine; partly because it is more dense than air, but also because a greater surface area of heated engine is exposed to the cooling medium (inside the water jacket as opposed to just the outside of the engine - if it were all about mass a solid engine block would cool better than one with a water jacket, right?)

However, the water, while absorbing heat quickly, becomes heat-saturated and must itself be cooled. So it is pumped to a device with lots and lots of fins, yet very little mass for it's size, to radiate the heat to the atmosphere (hence 'radiator').

Remember; disc brakes were developed for aircraft because they offered superior cooling over drum brakes, with less mass. Jaguar then began using them on their racing cars because they cool faster than drum brakes, allowing more aggressive braking in turns than the all-drum-brake competing racers at the time.

So now we have disc brakes with less mass and greater surface area exposed to cool air than drum brakes. The next step was to tap into the hot core of the metal to allow the heat to escape via crossdrilling.

Maguire

iTrader: (1)

i dont know if any of you read SCC, but a few years ago they did a 5 page article on a product called Cool Bakes. they were installed on a 3rd gen, so i dont know if they are available for a 1st gen yet. Cant recall all of the technical details at the moment (have to check out the old mag. when i get home.) but basically they are made of a composite material, similar to carbo-fiber. they disapate heat about 40% better than iron rotors. Again i dont remember the spec exactly, so dont quote me on this, and they weigh much much much less. I looked and couldnt find a web page. but they might be worth further investigating. Keep in mind, they do cost more.

Dyre

Thx for the help Jerky. I've been away, so i wasent able to get into this. Just something i wanted to add-

EDIT: **** tripod. dirrect link: http://reganrotaryracing.tripod.com/gcmande.htm
"Then I happened upon a set of front X-drilled brake rotors. They were in good condition, inexpensive, and looked nice on the car. I matched these with a pair for the rear. Well the gist of this tale is that after FIVE days on the track the front brake rotors exhibited those telltale signs of premature cracking and after only THREE days on the track the rear Xdrilled rotors had cracked to failure."

That would be from a relativly stock FD which has far suppior stock brakeing than any SA/FB ever built-

diabolical1

iTrader: (3)

well, i'd never heard of them until today. they look like a great idea (would've preferred 5-lug bolt pattern, but i'm not that greedy) ... my only concern would be the rotors, if and when they need replacing ... would you have to keep sending to Australia for them?