Crossdrilled or Not?

[speedminded]

Crossdrilling rotors has its advantages and disadvantages...they run cooler but are prone to cracking with extreme temperature differances ie. hitting a puddle during hard braking use. I don't foresee that happening because i doubt i'll be on the track in the rain and won't be driving hard on a wet street either (competition tires on a daily driver) Anyone have good or bad experience with any?

[Big Baller]

Crossdrilling rotors has its advantages and disadvantages...they run cooler but are prone to cracking with extreme temperature differances ie. hitting a puddle during hard braking use. I don't foresee that happening because i doubt i'll be on the track in the rain and won't be driving hard on a wet street either (competition tires on a daily driver) Anyone have good or bad experience with any?

Crossdrilled rotors do not in fact run cooler. They are prone to cracking. Slotted rotors eat pads. I can post up links to back up all this info if you like.

You are better off running regular rotors. If you go to Napa they generally carry two or three diffrent grade rotors for each car, just buy the best ones they have. Thats what I was open tracking my mustang on.

Matt

[SNapper]

cross drilled are for show. go ask the companies that sell rotors. they will tell you NOT to use cross drilled rotors for track use.

[speedminded]

Crossdrilled rotors do not in fact run cooler. They are prone to cracking. Slotted rotors eat pads. I can post up links to back up all this info if you like.

You are better off running regular rotors. If you go to Napa they generally carry two or three diffrent grade rotors for each car, just buy the best ones they have. Thats what I was open tracking my mustang on.

MattThe original purpose of crossdrilling rotors was to help release the gases emitted from the asbestos brake pads during braking. Any object with more surface area is going to cool faster, those holes are no differant than the principal behind a heat sink. Besides they look better too :tongue: As for grooved rotors...the caliper is an OEM rear from Porsche so the pads are dirt cheap.

http://forums.importatlanta.com/showthread.php?t=26848

I've been putting together a custom brake setup, the rotors will be ordered through AP Racing...it's not the typical one piece steel rotor, it's basically an outer ring bolted to an aluminum rotor hat/bell. It's actually the same rear rotor from a Modified circle track car...

[speedminded]

cross drilled are for show. go ask the companies that sell rotors. they will tell you NOT to use cross drilled rotors for track use.i'm referring to JGTC for what they use...why, who knows....just seems like they should know what they are doing :tongue: Some use cross drilled and some use slotted...the Takata NSX for example uses slotted only.

I'd like to start producing this kit, I have two other vehicles in mind and trying to obtain a control arm and hub from each to make a prototype.

[Big Baller]

The original purpose of crossdrilling rotors was to help release the gases emitted from the asbestos brake pads during braking. Any object with more surface area is going to cool faster, those holes are no differant than the principal behind a heat sink. Besides they look better too :tongue: As for grooved rotors...the caliper is an OEM rear from Porsche so the pads are dirt cheap.

http://

I've been putting together a custom brake setup, the rotors will be ordered through AP Racing...it's not the typical one piece steel rotor, it's basically an outer ring bolted to an aluminum rotor hat/bell. It's actually the same rear rotor from a Modified circle track car...

1 Find me proof that cross drilled rotors cool better. When you drill a rotor you lose mass, that mass is what absorbs and dissipates heat from the brake system. Taking mass out of the rotors isn't going to make them work better.

2 If you are going to the track you shouldn't be worried about how they look.

3. Have you done any track days? Regardless of how cheap the pads are you don't want to have to change them at the track if you can avoid it. Keep in mind that you wont be using stock pads at the track you will probably be on something similar to a Hawk hp + or Hp 1 and those aren't cheap.

4. Check out Coleman Racing they generally have better prices on blank rotors. They will also custom machine hats for you if need be. I have a very similar setup on my 240 track car. I ended up with slotted rotors because at the time that's all they had. Ill post up some of the links I have and you can decide for your self if you really want drilled rotors.




2. How do you know that you want your rotors to cool better.( what you actually want is for your rotors to stay in a certain temperature range so that they work effectively.

[Big Baller]

Here is a fairly good link on Honda-Tech not one of the sites I frequent but pretty good info anyways.

http://www.honda-tech.com/zerothread?id=1437513

[obd1kenobi]

Matt I'll beat you with some used cross-drilled rotors, then buy your mark ass a drink!

[speedminded]

1 Find me proof that cross drilled rotors cool better. When you drill a rotor you lose mass, that mass is what absorbs and dissipates heat from the brake system. Taking mass out of the rotors isn't going to make them work better.

2 If you are going to the track you shouldn't be worried about how they look.

3. Have you done any track days? Regardless of how cheap the pads are you don't want to have to change them at the track if you can avoid it. Keep in mind that you wont be using stock pads at the track you will probably be on something similar to a Hawk hp + or Hp 1 and those aren't cheap.

4. Check out Coleman Racing they generally have better prices on blank rotors. They will also custom machine hats for you if need be. I have a very similar setup on my 240 track car. I ended up with slotted rotors because at the time that's all they had. Ill post up some of the links I have and you can decide for your self if you really want drilled rotors.

2. How do you know that you want your rotors to cool better.( what you actually want is for your rotors to stay in a certain temperature range so that they work effectively. Both our Honda Challenge cars, all 3 of our Formula Mazda's, and Pro Formula mazda use plain face/blank rotors. i'm not arguing whether cross drilled is better or not...I just see them used in race applications and on nearly every motorcycle produced. Why i ask? I can understand for looks on a bike but what about $750,000-1,000,000 race cars? Are their crew members and engineers just as confused as i am? I would hope not.

Mass only dissipates heat because it has more exposed surface area. Why wouldn't a heat sink just be made as a simple square block if that wasn't true? BUT to go with your theory, it obviously takes less time to heat up less mass (a smaller pot of water will boil faster)...so by drilling holes or cutting slots then the rotor in theory it will heat up faster because there is less mass...BUT that resorts back to my theory on more exposed surface area means more heat dissipation...So would it all equal out at the end?

I can't access h-t from work so someone may have already done this on there but all the math and science in the world means nothing to most without putting it to test. I'll personally put a crossdrilled rotor on one side and a plain face on the other and test it myself. I'll use heat paint and a pyrometer to get the results and we'll see if in fact there is any and what differances. That's the only way.

In a 12 or 13 hour endurance race we'll go through 2 sets of hawk/carbotech race pads with the exact same brake setup using plain faced rotors on a 2,100 lb car (dry weight/del sol). Changing the pads on them couldn't be easier but my car isn't going to see competive racing for quite a while, if ever...I'll just stick with track days and mountain runs :-)

Really the only reason i would go with the crossdrilled is to show it off...i want to produce and market this kit and if it helps sell just 1 setup because it looks good then it's done it's job ;)

[Vteckidd]

Plain Rotors, Carbotech pads, stainless lines, 91 EX master cylinder, thats all you need

[speedminded]

Plain Rotors, Carbotech pads, stainless lines, 91 EX master cylinder, thats all you needbut but..! I like to be differant, you know i've been talking about the calipers for nearly a year now, hell...bought them like 8 months ago and still haven't got them on.

I'm running the 2000-2001 ABS system too but the ridges on my passenger side axle are just about non-existant...not sure how that's gonna effect it.

[IntegraXTR]

91 EX master cylinder, explain?

[Big Baller]

Heres a link

http://corner-carvers.com/altimathread.php.html

Its a long thread, feel free to discuss

More links less forums

http://www.teamscr.com/grmbrakes.htm
http://www.teamscr.com/rotors.htm
http://www.stoptech.com/tech_info/te...e_papers.shtml
http://www.howstuffworks.com/tire.htm
http://www.howstuffworks.com/fpte.htm

[Vteckidd]

91 EX master cylinder, explain?
biggest master cylinder honda made besides the ITR , only came on the 1991 4 door EF EX model, rare to find

[KevinT707]

I'm willing to risk the cracks that are possible on drilled rotors & the slots that eat up brake pads. I just don't want it to happen to often, cause I just like they way they look. On average with normal driving how long would it take for me to go through some normal brake pads w/ drilled & slotted rotors, Big Baller? Cause it seems like its taking forever on my stock brake setup right now, I haven't replaced the pads in 2 years.

[speedminded]

I'm willing to risk the cracks that are possible on drilled rotors & the slots that eat up brake pads. I just don't want it to happen to often, cause I just like they way they look. On average with normal driving how long would it take for me to go through some normal brake pads w/ drilled & slotted rotors, Big Baller? Cause it seems like its taking forever on my stock brake setup right now, I haven't replaced the pads in 2 years.I got a little over 40k miles out of my last set of brake pads and i've been working downtown for 2+ years too, plus all the mtn runs...wonders of a manual transmission and quality clutch :)

[mp5o]

IIRC The high end cars/race cars do not use cross DRILLED rotors. They are cast(or w.e.) that way. Take a somewhat thin piece of steel and try to bend it.... Wont bend right? Now drill holes in it.... Now it bends...

[SampaGuy]

if the car is for the street, just get the plain brembos

[Big Baller]

IIRC The high end cars/race cars do not use cross DRILLED rotors. They are cast(or w.e.) that way. Take a somewhat thin piece of steel and try to bend it.... Wont bend right? Now drill holes in it.... Now it bends...

No they arent, the holes are not cast. I will pay for a picture of the casting process where rotors are cast with the holes.

[Vteckidd]

bottom line, when it comes to the best PERFORMANCE, its brembo blanks, good pads (hawk, carbotech panthers), stainless lines, an the best master cylinder for your vehicle.

go to honda-tech, post a topic in the autox an road race forum, i GUARANTEE 99.9% of the guys do NOT use crossdrilled or slotted rotors.

the questions you need to ask are:
how much braking am i doing?
how much HARD braking am i doing?
will my brakes see a benefit from cross drilled/slotted rotors?
what temp are my rotors getting to?
what is "too hot"?

most guys i know that seriously race, would rather spend the moeny on a custom brake duct or ram air induction to cool their brakes over crossdrilled or slotted rotors.

its like guys taht want to buy the $2000 fully adjustable dampening Tein suspension. i ususally ask them, "how often are you really going to adjust your suspension." the answer is usually they install it an never touch it again, so why spend the money on the adjustable setup then?

[mp5o]

No they arent, the holes are not cast. I will pay for a picture of the casting process where rotors are cast with the holes.

Im not 100%... Hence the IIRC. Its based off hearsay. Thanks for the correction.

[BLk92DA]

i have crossed drilled slotted rotors on all four. the braking is superb with ceramic pads...but im begining to see little cracks in the hole of the rotors(due to me washing car while hot)
i wouldnt suggest gettin these if you were to autox ect. just get whats best for your application

[speedminded]

Ok, i have read 1,000's of threads, posts, reviews, and tech articles...Even though i have found ZERO brake dyno or any other physical testing information as a whole it appears cross drilled brakes are purely cosmetic and only used as a hoax for the increased sales of higher end sports cars and more expensive "upgraded" brake systems.

Nearly every single company mentioned above that claimed that cross drilling offers no advantages does in fact claim somewhere that they operate cooler...from Power Slot to Brembo to AP Racing. Is it a scam? What's the deal? who knows?

[Big Baller]

i have crossed drilled slotted rotors on all four. the braking is superb with ceramic pads...but im begining to see little cracks in the hole of the rotors(due to me washing car while hot)
i wouldnt suggest gettin these if you were to autox ect. just get whats best for your application


If you are seeing little cracks you need to throw them away now. They are trash, they could come apart at any minute.

[mp5o]

Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that tells you that drilling makes the disc run cooler is smoking crack."

Power Slot: "At one time the conventional wisdom in racing circles was to cross-drill brake rotors to aid cooling and eliminate the gas emitted by brake pads. However, today?s elite teams in open wheel, Indy and Trans Am racing are moving away from crack prone, cross-drilled brake rotors in favor of rotors modified with a fatigue resistant slotting process."

Stop Tech: "StopTech provides rotors slotted, drilled or plain. For most performance applications slotted is the preferred choice. Slotting helps wipe away debris from between the pad and rotor as well as increasing the "bite" characteristics of the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage. Many customers prefer the look of a drilled rotor and for street and occasional light duty track use they will work fine. For more severe applications, we recommend slotted rotors." (Note that even though Stop Tech sells both drilled and slotted rotors they do not recommend drilled rotors for severe applications.)

Wilwood: "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."

From Waren Gilliand: (Warren Gilliland is a well-known brake engineer in the racing industry and has more than 32 years experience in custom designing brake systems ...he became the main source for improving the brake systems on a variety of different race vehicles from midgets to Nascar Winston Cup cars.) "If you cross drill one of these vented rotors, you are creating a stress riser that will encourage the rotor to crack right through the hole. Many of the rotors available in the aftermarket are nothing more than inexpensive offshore manufactured stock replacement rotors, cross drilled to appeal to the performance market. They are not performance rotors and will have a corresponding high failure rate"

From Baer: "What are the benefits to Crossdrilling, Slotting, and Zinc-Washing my rotors?
In years past, crossdrilling and/or Slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads...However, with today?s race pad technology, ?outgassing? is no longer much of a concern...Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer?s offerings."

Grassroots Motorsports: "Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)

AP Racing: "Grooves improve 'cleaning' of the pad surfaces and result in a more consistent brake performance. Grooved discs have a longer life than cross-drilled discs." ...

[BLk92DA]

If you are seeing little cracks you need to throw them away now. They are trash, they could come apart at any minute.

squint your eyes little?

[Big Baller]

no

[BLk92DA]

so no, as in they're ok correct?

[speedminded]

oh well, can't get the larger size rotor i wanted so stuck with 11.75".

[Jaimecbr900]

I have been a part in huge debates about this subject and the advantages/disadvantages of BBK's.

I have slotted front and slotted/drilled rears. When my rears need to be replaced, I'll do it with front matching slotted. I've never had issues with cracking in any of my rotors in any of my cars. I've ran them at tracks and especially in the mountains.

I've noticed that pads and size of the BBK's makes far more difference than if it's cross-drilled or not.

[Outphase]

Brembo blanks or Blanks of your choice...OEM size, and some nice pads like Hawk Pad HP+... and you're good to go.

[speedminded]

Brembo blanks or Blanks of your choice...OEM size, and some nice pads like Hawk Pad HP+... and you're good to go.Maybe, but why not go all out if you have the sources to build a kit :) The Porsche calipers have 20% larger pads and going from a solid rotor to one that is 15% larger and vented. Steel braided lines, extended stud's, and spacing the wheels a several MM's (however much it takes to get the wheels to fit). Cheapest Brembo kit for my car is $2,400...I have a little more than 10% into it ;)

[Outphase]

Definetly sounds good. Let me see your car. Haha.

[Outphase]

...wait a sec, I think I might have seen your car at mall of georgia once.

[speedminded]

...wait a sec, I think I might have seen your car at mall of georgia once.doubt it...it rarely gets left out there...very rarely but it is possible.

Click the link in my sig...may have a mtn run this sunday too.

[DrivenMind]

I had crossdrilled rotors on my Maxima, and didn't have an issue with cracking. But when I got the Corolla I went ahead and chose to go with Brembo blanks and Hawk Pads which work quite well on a 2200lbs car, shod with a sticky tyre.

[Outphase]

doubt it...it rarely gets left out there...very rarely but it is possible.

Click the link in my sig...may have a mtn run this sunday too.

I'm not doing anything this sunday, where you headed to? I'd like to go.

[speedminded]

I'm not doing anything this sunday, where you headed to? I'd like to go.Planned a mtn. run for next weekend but have a decent group wanting to go this weekend... http://forums.importatlanta.com/showthread.php?p=34609039#post34609039

[BLk92DA]

doubt it...it rarely gets left out there...very rarely but it is possible.

Click the link in my sig...may have a mtn run this sunday too.


lolz i seen you parked at D's driveway the other night haha...P.I.M.P

[speedminded]

lolz i seen you parked at D's driveway the other night haha...P.I.M.PShhhhh ;)

[BTEC]

SLOTTED

[BLk92DA]

speedminded sho did slotted the broad!

[SiR_Boost]

just get what makes you happy

[speedminded]

just get what makes you happylolol, this is the tech area isn't? I think function overrides what makes someone "happy"...not to mention how the heck are you going to know unless you buy all of them testing each one :slap:

[SiR_Boost]

i know i was just trying to get a few laughs out of it..hehe! :bigok:
but in all seriousness i wouold get crossed or drilled and slotted. really they are more for looks unless you are upgrading the size and such. drilled ones were originally used to allow gases to escape to oyu could have quick stopping time instead of a slow one. slotted were used to clean the surface of the pad as to keep a good friction between the pad and the rotor. but still i say get what makes you happy the most....

[speedminded]

i know i was just trying to get a few laughs out of it..hehe! :bigok:
but in all seriousness i wouold get crossed or drilled and slotted. really they are more for looks unless you are upgrading the size and such. drilled ones were originally used to allow gases to escape to oyu could have quick stopping time instead of a slow one. slotted were used to clean the surface of the pad as to keep a good friction between the pad and the rotor. but still i say get what makes you happy the most.... i actually went with plain, might not look the best but looking more for function...and i seriously doubt i'll have glazing problems so wasn't too worried about getting slotted...


http://forums.importatlanta.com/attachment.php?attachmentid=53572&stc=1

http://forums.importatlanta.com/attachment.php?attachmentid=53574&stc=1

[SiR_Boost]

love those wheels dude. you got the porsche caliper cover sweet.

[BLk92DA]

all that money you put into your braking/suspension and u cant afford a "REAL" ITR LOL!

[speedminded]

love those wheels dude. you got the porsche caliper cover sweet.lolol...

all that money you put into your braking/suspension and u cant afford a "REAL" ITR LOL!lolol, the Tein Flex i bought off an ex-gf when she was selling her integra and i wouldn't let her sell the car with them on....only a couple months old and $500 ;) The Brembo monoblock calipers were $270 from a Porsche junkyard off a '98 Boxster...the $600 in rotors, hats, conversion brackets, arp studs, stainless lines, etc. was traded for labor with the race team i crew for...so technically i have $770 total in suspension and brakes :tongue:


Tein Flex for DC2 - $1,400
Brembo big brake kit for DC2 - $2,400

Total = $770 :D

[speedminded]

more pics :camera:

[Big Baller]

Very nice, who machined the brackets for you.

Matt

[IntegraXTR]

man talk about stopping power, nice setup jason, glad to see you finally put them on instead of sitting around in your garage, bout damn time!

[magneto198]

Great write-up i found on the difference between the two types of rotors, along with explanations and reasons for warping. Enjoy!

CROSS-DRILLED ROTOR OVERVIEW

You buy cross-drilled or slotted rotors for performance right? Well they say, "Cross Drilled Discs will last up to twice as long as O.E.M. rotors (depending on your braking style)." That little parenthetical statement should give you a clue! Most people that are going to buy cross-drilled rotors are going to buy them because they drive harder, demand more out of their braking system, hence a more aggressive braking style. I warped my Brembro cross-drilled rotors in about 2 years.... and I was in school...my car sat most of the time.

I agree with these two statements, within a certain extent "40% Better Cooling, 20% better stopping; Improved Wet Braking"

This statement is very misleading, "Lower Brake Temperature Reduces Rotor Warpage” Yes your normal operating brake temperature may be lower, and yes your rotors may cool a little faster, however lower operating temperature and cooling speed aren't major players in warpage. Actually, cooling something faster will warp it faster then a gradual cool down.

Again...very misleading, "Less Brake Fade and Longer Life" Yes they reduce brake fade, by keeping operating temperatures down. However brake fade is more attributed to the compound material on the brake pad itself. Same rotor with different pad material (ex. organic, and semi-metallic or carbon metallic) will exhibit totally different temperature range, braking performance, and life expectancy. The reason OEM brakes fade like hell is the pad compound, it's organic. I could nuke a set of organic pads in no time flat...cause their level of heat tolerance is so much lower than a semi or carbon metallic pad. However they are quieter, and since Joe Public doesn't give a **** about how their car performs, they just want it to go from point A to B, it don't matter. However for the few that want better performance you need to step up to a better pad.

GAS SLOTTED ROTOR OVERVIEW

Ok before I look at what they said, one thing should be noted. Look at how one sided their two pages are for cross-drilled rotors...hmmmm.

Ok first thing they say "Enhanced Initial Bite" Sure this gives you may get a stronger "BITE" from the slot, BUT that is NOT what it is there to DO!! The slots on the rotors are to vent the build up of gasses produced in the interface between the rotor and the brake pad material! That is really all they're meant to do. Some brake pads have a slot down the middle, this slot also helps release those gasses. Main thing is, if you have gasses between the rotor and the pad, you loose braking performance, you do not have as solid a direct contact between the two.

"Intended For Track Use" I can say the same for cross-drilled, this statement is TOTALLY OPINION and should not be on a page comparing slotted and cross-drilled!

I'll agree with this "Better Cleaning of Pad Friction Material" Yes over time the pad material will get a glazed surface on it. The slots will help wipe this glaze away, or keep it from forming. However...this is trivial.

Again....more misleading information, "Slotted discs offer cleaning of the friction material (brake pads), but do little in terms of additional heat dissipation. Slotted brake discs do not cool better than cross-drilled discs or even standard discs. The face grooves will slice the brake pad material allowing the pad to bite harder into the disc, therefore causing an increase in disc temperatures. This is recommended for competition vehicles to bring pads and disc temperatures up to optimal operating ranges. (Race cars warm-up engines, tires and brakes for the best possible performance)."

The thing they are pushing in this paragraph is how much better the cooling is with cross-drilled rotors, and that slotted add heat. The main thing I find very misleading is, with ANY rotor-pad combo, you will have heat generation from driving...even if you DO NOT touch the brakes AT ALL. Rotors drag against the pads. You will get heat build up. Your rotors and brakes are designed to work better with a little heat in them. Ever drive you car first thing in the morning on a cold day. The brakes aren't too good when they are cold, so why do you need to excessively cool these rotors that are going to generate heat anyway? (Exception is organic pads...they work decent when cold, but better when a little warmer)

MAJOR POINTS MISSED BY THESE TWO ARTICLES

https://www.kvrperformance.com/world/world.html

There are several key points that they failed to mention, rotor warpage and the main cause of it. The main cause of warpage in any material, object, whatever is heating it beyond a certain point where plastic deformation occurs, now there’s really no force being put on the rotor that it can’t handle, our force is heat, so think of heat being a force and there is a curve that this material will follow on when it is heated and cooled. Think of warpage when the material is pushed past a certain point along this curve.

Also cyclic loading of a material will also cause failure, or warpage in our case. Heating up and cooling of a rotor is our cyclic loading. Again, the more rapidly you do this, the greater your chances are for warpage. So if you go drive like a crazy person and then park your car the rotors will cool faster then if you drove nicely around for a couple miles to slowly bring them down in temperature.

That brings me to my next point, When you drive your car hard, and park it, the part of the rotor which is exposed to air cools at a different rate then the part that is touching the pad material. The pad material will retain heat a lot longer then the air, so you will get a spot on the rotor where the pad sat that will be warped. A friend of mine who works in motor sports, Indycar to be exact, told me that during a practice session they would go through rotors, i.e. warp them faster then they would if they were in a race. The main reason, like I said above, is the cyclic cooling of the rotors from really hot to cold, and the “hot spot” from the brake pad.

The main point or problem with what they say about warpage has to do with something they talk about, heat dissipation. They say that they have increased heat dissipation with cross-drilled rotors. This is partially true. At lower to medium temperatures the holes in the rotor allow more surface area, and as any good mechanical engineer or thermal scientist knows, you can achieve better cooling with more surface area. The holes in the rotor sort of act like the fins in your radiator, they aid in cooling the rotor. However those holes are a double-edged sword. They actually do more damage then they are supposed to help. When you cross drill a rotor, you take material out of it. Well guess what, that material is what helps that rotor maintain a certain level of performance before it warps. The more material you have the better heat distribution you get through the object. Think of it as I said before, a curve that this rotor follows when it is heated and cooled, and there is a certain plateau or ceiling where warpage occurs. When you remove material from the rotor, you decrease this ceiling. So it actually takes less heat to warp the rotor then it did before you started drilling holes in it. So if you look at the cooling by the holes in comparison to the loss of heat dissipation or heat tolerance that the rotor can handle, you have a balance scale. What is more important? Well In my book, I would want that ceiling to be as high as it could be to ward off the effects of warpage. Who cares if you rotor runs slightly cooler for normal use, and may cool slightly faster. The main thing they were saying was that cross-drilled reduces brake fade. This is 1/10 correct, better pads reduce brake fade.

Another thing, heat flows through the rotor as it heats up. With a normal rotor this heat is evenly dispersed and expelled. With the holes in cross-drilled rotors you get an interruption in this heat flow through the rotor. You again get hot spots or points where the material is discontinuous, and with these discontinuous points you get added stresses or higher temperatures at these discontinuities. So if you would look at a thermal image of a normal rotor you would see an evenly spaced out heat flow in the rotor. With cross-drilled you will see cold and hot spots in certain areas of the rotor. Temperature is a cyclic force and over time, with these hot spots occurring around the holes you end up with cracks, where the material has failed.

One last thing, there is actually a formula to calculate how much material can safely be removed from a rotor without compromising it’s ability to dissipate the heat generated in it. So with larger rotors you can have more or the same amount of holes and it don’t matter, there is plenty of material there. But with smaller rotors there is less material so you either need fewer holes to maintain a safe amount of material to dissipate the heat or you will lower the “ceiling” at which the rotor will warp.

CONCLUSION

Ok to sum everything up. Cross-drilled rotors are good for fast heat dissipation and reduction in braking gasses, however they are prone to warpage because of their less amount of material, and lower peak temperature tolerance. They are good for racing applications where you need very fast cooling from high-speed stops, and where they don’t care about the longevity of the rotors. They are not practical if you want to get more life out of your rotor. Slotted rotors main advantage is that they help get rid of the braking gasses between the rotor and pad. They are good for mild to medium racing applications and for the performance minded street driver. The longevity will be greater then that of cross-drilled, yet may be a little less then stock. There are also high performance rotors that offer a combination of both slotting and cross-drilling.

I guess now you may be asking what gives him the authority or background to be saying all this. Well first off I have gone through the hassles of cross-drilled rotors myself, and had the down sides of cross-drilling happen to me. Secondly I have researched and found NON-BIAS articles and information on the two types of rotors, as well as consulted several automotive professionals on the topic. Next I am a mechanical engineering major at Penn State, and have had courses in the areas I have talked about, the stresses, cyclic loading, temperature, discontinuities, and heat transfer. So I’m not just talking out of my ass on these things. And finally, like other performance-minded drivers I too want to get the most out of my car, and have looked into the different possibilities and options.

[speedminded]

Great write-up i found on the difference between the two types of rotors, along with explanations and reasons for warping. Enjoy!

CROSS-DRILLED ROTOR OVERVIEW

You buy cross-drilled or slotted rotors for performance right? Well they say, "Cross Drilled Discs will last up to twice as long as O.E.M. rotors (depending on your braking style)." That little parenthetical statement should give you a clue! Most people that are going to buy cross-drilled rotors are going to buy them because they drive harder, demand more out of their braking system, hence a more aggressive braking style. I warped my Brembro cross-drilled rotors in about 2 years.... and I was in school...my car sat most of the time.

I agree with these two statements, within a certain extent "40% Better Cooling, 20% better stopping; Improved Wet Braking"

This statement is very misleading, "Lower Brake Temperature Reduces Rotor Warpage” Yes your normal operating brake temperature may be lower, and yes your rotors may cool a little faster, however lower operating temperature and cooling speed aren't major players in warpage. Actually, cooling something faster will warp it faster then a gradual cool down.

Again...very misleading, "Less Brake Fade and Longer Life" Yes they reduce brake fade, by keeping operating temperatures down. However brake fade is more attributed to the compound material on the brake pad itself. Same rotor with different pad material (ex. organic, and semi-metallic or carbon metallic) will exhibit totally different temperature range, braking performance, and life expectancy. The reason OEM brakes fade like hell is the pad compound, it's organic. I could nuke a set of organic pads in no time flat...cause their level of heat tolerance is so much lower than a semi or carbon metallic pad. However they are quieter, and since Joe Public doesn't give a **** about how their car performs, they just want it to go from point A to B, it don't matter. However for the few that want better performance you need to step up to a better pad.

GAS SLOTTED ROTOR OVERVIEW

Ok before I look at what they said, one thing should be noted. Look at how one sided their two pages are for cross-drilled rotors...hmmmm.

Ok first thing they say "Enhanced Initial Bite" Sure this gives you may get a stronger "BITE" from the slot, BUT that is NOT what it is there to DO!! The slots on the rotors are to vent the build up of gasses produced in the interface between the rotor and the brake pad material! That is really all they're meant to do. Some brake pads have a slot down the middle, this slot also helps release those gasses. Main thing is, if you have gasses between the rotor and the pad, you loose braking performance, you do not have as solid a direct contact between the two.

"Intended For Track Use" I can say the same for cross-drilled, this statement is TOTALLY OPINION and should not be on a page comparing slotted and cross-drilled!

I'll agree with this "Better Cleaning of Pad Friction Material" Yes over time the pad material will get a glazed surface on it. The slots will help wipe this glaze away, or keep it from forming. However...this is trivial.

Again....more misleading information, "Slotted discs offer cleaning of the friction material (brake pads), but do little in terms of additional heat dissipation. Slotted brake discs do not cool better than cross-drilled discs or even standard discs. The face grooves will slice the brake pad material allowing the pad to bite harder into the disc, therefore causing an increase in disc temperatures. This is recommended for competition vehicles to bring pads and disc temperatures up to optimal operating ranges. (Race cars warm-up engines, tires and brakes for the best possible performance)."

The thing they are pushing in this paragraph is how much better the cooling is with cross-drilled rotors, and that slotted add heat. The main thing I find very misleading is, with ANY rotor-pad combo, you will have heat generation from driving...even if you DO NOT touch the brakes AT ALL. Rotors drag against the pads. You will get heat build up. Your rotors and brakes are designed to work better with a little heat in them. Ever drive you car first thing in the morning on a cold day. The brakes aren't too good when they are cold, so why do you need to excessively cool these rotors that are going to generate heat anyway? (Exception is organic pads...they work decent when cold, but better when a little warmer)

MAJOR POINTS MISSED BY THESE TWO ARTICLES

https://www.kvrperformance.com/world/world.html

There are several key points that they failed to mention, rotor warpage and the main cause of it. The main cause of warpage in any material, object, whatever is heating it beyond a certain point where plastic deformation occurs, now there’s really no force being put on the rotor that it can’t handle, our force is heat, so think of heat being a force and there is a curve that this material will follow on when it is heated and cooled. Think of warpage when the material is pushed past a certain point along this curve.

Also cyclic loading of a material will also cause failure, or warpage in our case. Heating up and cooling of a rotor is our cyclic loading. Again, the more rapidly you do this, the greater your chances are for warpage. So if you go drive like a crazy person and then park your car the rotors will cool faster then if you drove nicely around for a couple miles to slowly bring them down in temperature.

That brings me to my next point, When you drive your car hard, and park it, the part of the rotor which is exposed to air cools at a different rate then the part that is touching the pad material. The pad material will retain heat a lot longer then the air, so you will get a spot on the rotor where the pad sat that will be warped. A friend of mine who works in motor sports, Indycar to be exact, told me that during a practice session they would go through rotors, i.e. warp them faster then they would if they were in a race. The main reason, like I said above, is the cyclic cooling of the rotors from really hot to cold, and the “hot spot” from the brake pad.

The main point or problem with what they say about warpage has to do with something they talk about, heat dissipation. They say that they have increased heat dissipation with cross-drilled rotors. This is partially true. At lower to medium temperatures the holes in the rotor allow more surface area, and as any good mechanical engineer or thermal scientist knows, you can achieve better cooling with more surface area. The holes in the rotor sort of act like the fins in your radiator, they aid in cooling the rotor. However those holes are a double-edged sword. They actually do more damage then they are supposed to help. When you cross drill a rotor, you take material out of it. Well guess what, that material is what helps that rotor maintain a certain level of performance before it warps. The more material you have the better heat distribution you get through the object. Think of it as I said before, a curve that this rotor follows when it is heated and cooled, and there is a certain plateau or ceiling where warpage occurs. When you remove material from the rotor, you decrease this ceiling. So it actually takes less heat to warp the rotor then it did before you started drilling holes in it. So if you look at the cooling by the holes in comparison to the loss of heat dissipation or heat tolerance that the rotor can handle, you have a balance scale. What is more important? Well In my book, I would want that ceiling to be as high as it could be to ward off the effects of warpage. Who cares if you rotor runs slightly cooler for normal use, and may cool slightly faster. The main thing they were saying was that cross-drilled reduces brake fade. This is 1/10 correct, better pads reduce brake fade.

Another thing, heat flows through the rotor as it heats up. With a normal rotor this heat is evenly dispersed and expelled. With the holes in cross-drilled rotors you get an interruption in this heat flow through the rotor. You again get hot spots or points where the material is discontinuous, and with these discontinuous points you get added stresses or higher temperatures at these discontinuities. So if you would look at a thermal image of a normal rotor you would see an evenly spaced out heat flow in the rotor. With cross-drilled you will see cold and hot spots in certain areas of the rotor. Temperature is a cyclic force and over time, with these hot spots occurring around the holes you end up with cracks, where the material has failed.

One last thing, there is actually a formula to calculate how much material can safely be removed from a rotor without compromising it’s ability to dissipate the heat generated in it. So with larger rotors you can have more or the same amount of holes and it don’t matter, there is plenty of material there. But with smaller rotors there is less material so you either need fewer holes to maintain a safe amount of material to dissipate the heat or you will lower the “ceiling” at which the rotor will warp.

CONCLUSION

Ok to sum everything up. Cross-drilled rotors are good for fast heat dissipation and reduction in braking gasses, however they are prone to warpage because of their less amount of material, and lower peak temperature tolerance. They are good for racing applications where you need very fast cooling from high-speed stops, and where they don’t care about the longevity of the rotors. They are not practical if you want to get more life out of your rotor. Slotted rotors main advantage is that they help get rid of the braking gasses between the rotor and pad. They are good for mild to medium racing applications and for the performance minded street driver. The longevity will be greater then that of cross-drilled, yet may be a little less then stock. There are also high performance rotors that offer a combination of both slotting and cross-drilling.

I guess now you may be asking what gives him the authority or background to be saying all this. Well first off I have gone through the hassles of cross-drilled rotors myself, and had the down sides of cross-drilling happen to me. Secondly I have researched and found NON-BIAS articles and information on the two types of rotors, as well as consulted several automotive professionals on the topic. Next I am a mechanical engineering major at Penn State, and have had courses in the areas I have talked about, the stresses, cyclic loading, temperature, discontinuities, and heat transfer. So I’m not just talking out of my ass on these things. And finally, like other performance-minded drivers I too want to get the most out of my car, and have looked into the different possibilities and options.Interesting, I didn't think outgassing was an issue anymore....in the last 40+ years anyways?

[Pavlo]

Blanks are the best, all the others are for looks. And for those who will bitch "formula 1 uses drilled", no it doesn't I'll upload some pics of F1 brakes once I get home.

[§treet_§peed]

formjula one uses crossed drilled and slotted carbon fiber brakes...

[Kyle]

Visually crosdrilled for me. But functionally I would have to say Slotted.

[speedminded]

formjula one uses crossed drilled and slotted carbon fiber brakes...carbon fiber? lol, carbon fiber discs wouldn't stop a bicycle ;) It's just carbon or now [which you could consider yourself semi-correct] is carbon fiber reinforced ceramic aka Carbon-Silicon Carbide...still no crossdrilling or slotting involved.

[§treet_§peed]

:werd:^^ i had watched this showon the speed channel about Formula one cars and herd it but wasn't sure if it was just carbon brakes or carbon fiber....man those bitches were glowing bright ass red but still stoping on a dime lol...

[phatrabbitzz]

I'd stick with plain brembo rotors for street use.

[cornercarver78]

Drilled or slotted and "milled" (can be done on simple brake lathe) to reduce unsprung weight gosh! :crazy:

[Big Baller]

Drilled or slotted and "milled" (can be done on simple brake lathe) to reduce unsprung weight gosh! :crazy:

Fucking Damn it, did you not read any of the shit that I posted, do you not understand that decreasing the weight of the rotor itself actually decreases its ability to dissipate heat.

Lighter Rotors are not the answer.

[cornercarver78]

Fukin' gawd damnit turd eatin sum' bitch... thet thurs what you call sarcasm. :goodjob: and while I wasn't serious, reducing unsprung weight increases the efficiency of the suspension.

[Big Baller]

Turn or Stop you pick