4CN Air

iTrader: (7)

highly doubt it, and why? Buy non drilled of the proper size and good pads and be happy that you look cool by stopping quickly!

Morondongon

Damn Jimlab, i think that i have had more fun reading your post than actually reading the thread... but you are right though... some of this people just want to post a stupid comment without reading anything...
I personnally thought that Crossdrilled were better than slotted and that a combination of the two was the way to go, but now that i read the most of the thread (the first 3 pages, don't need to read no more) i think that i when am due to for brakes am going to buy what's going to give me better performance not better looks...

concept-R

I am far from being a dedicated racer, but I do take advantage of the summer months to track and autox my car.

Back in the day, I was one of the fools who believed that cross-drilled rotors performed better than stock. I learned the expensive way that it was not the case (I got cracking after 3 stints on the track using performance pads, fluids and SS lines). I switched back to stock and my car's solid vented rotors performed better on the track and on the street.

In my FC, I am running 15+ year old brakes and they bite very well so far. If anything, to improve braking performance, I will do what I did with my other cars--SS brake lines, better pads, and better fluids on the stock braking system. If I require even better braking than that, then I'll go with a slightly larger rotor and work up from there.

concept-R

Maybe it was something like this...

SidewaysGts

3rd post, Go me! (boy this is gonna be long)

So do drilled rotors cool rotors compared to non drilled rotors? Someone mentioned youve less mass to disipate the heat, so in that sense they dont cool as well. Well that IS true- in that they have less metal to disipate the heat, but then lets keep in mind your reducing the mass of the rotor, so the rotor has less potential to store heat in the first place, this alone leads to cooler temperatures. Theres also the fact with these hole the less mass comes increased surface area to vent that heat into the air. Companies like KVR have done tests to show drilled rotors can disipate heat up; to 20% faster then non drilled rotors.

Think of it like this, whats going to cool down faster, a glass of hot water of a tub full of hot water. Bitch if you want about this being water not metal. So go ahead and try this instead, Take 2 pieces of steel (hell make them of equal proportions for arguments sake) And put them in the oven and heat them to the same temperature, see which one cools down faster.

The "up" of less mass and increased surface area though of course has a down, a double edge. A point already strongly enforced, is increased surface area leads to more stress points the rotor is physicaly capable of. Also theres a fact your not only removing mass from the rotor, your removing structural integrity/enforcement.

Slotted rotors do the same as drilled to a slightly lesser extent immediatley, but without the higher compromise in durability. Theres less mass to heat up, more surface area to disipate heat, and no complete hole so the loss in integrity isnt nearly as severe.

Something else to point out is though the out-gas effect though not as great as it once was, the effect is still there. The organic materials that hold the pad together will generally start to go first, even the metal in common semi-metalic pads will start to melt if temperatures get too hot. These obviously first start as a liquid and creates that "hydroplane" effect on the rotor, and quickly turns into a gas which actualy resists the pad pressing against the rotor. Drilled holes and slots give an area for the liquid/gas to go to without resisting the pad.

About the nascar and open wheeled indy carts/f1 vehicles (ando ther vehicles etc) using slotted over drilled, apples to oranges. Keep in mind these events are endurance events, why risk a rotor braking and handicaping you into the pits even longer when you could be out on the track? considering how hard these vehicles need to constantly be braking and the lower durability drilled rotors- endurance is critical.

This all comes from what ive read seen and experienced coupled with a fairly basic and simple under standing of physics. I will say neither drilled nor slotted rotors preform better, if you get the feeling ive implied that please wipe that from your head- which type of rotor can provide better results depends on what you think youll be doing. If you want to argue with something ive said by all means have at it, but please try argue with physics and actual tests/restuls, not something someone or some company has said, after all- they are still a company.. that is strongly the business of advertising.

Someone mentioned testing both drilled and slotted rotors before, funny the drilled cracked badly after a day of hard use, and the slotted warped. Think about what ive said, and what casues the cracks, and what causes the waping.

Sorry to make this so long- congrats if you actually read through all of it.

DamonB

It works the other way around as well. Take a glass of water and a tub of water and apply the same amount of heat. Which one boils first? The rotor with the least mass will heat up faster and then be so hot that it cannot shed it's heat quickly enough. If your argument were true nobody on earth would need big brake rotors to keep from overheating the brakes...

If you're pads are melting or turning to liquid then quite obviously the pads are too hot and how your brake rotor is made will be the least of your problems.

No sh*t, and those races are only a couple hours long. If you're willing to buy crossdrilled rotors every couple hours then go ahead.

...and the top racing brake manufacturers in the world disagree with everything you said:

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."

also from AP: "Cross drilled...can compromise disc life. Radiused drilled...mainly used for aesthetic reasons on road applications."

SidewaysGts

Good point, but its potential to hold heat is still lower then that of a normal rotor- you may reach it faster but its still not going to be as high, and youll still disipate that amount of heat faster when off the brakes.

Back into racing applications the lighter massed rotors will heat up -quicker- this does not mean their temperatures will exceed what non drilled rotors will reach with more efficient ability to dispense heat. This results in less pad-fade and brake fade, meaning you can be on the brakes less in general- its a nice little circle.

Follow the conversion chart there, Sold - Liquid - Gas, to go from solid to gas is called sublimation, generaly not something a pad does. The time from solid to liquid to gas is very minimal but the effect is still there. Im sure uve seen when rotors glow red from exxesive use, what do you think happens to the small metal particles in semi-metalic pads? they dont exactly turn red and chip away.

And here i almost forgot Rx-7 club and its notoriety for flaming and generaly "nice" comments. A few hours of the exentive abuse the rotors face is extreme.

"if you're willing to buy crossdrilled rotors every couple hours then go ahead"

Now, did i ever say this or something along the lines to imply this as my intention? Please quote me if i said otherwise, and here i thought i was trying to get across the point slotted is superior for endurance related issues that drilled rotors would be unable to be up for... silly me.

Yay for them? As i said i was speaking from a physics stand point- something i tend to believe cars follow and are ruled by. Argue with them not with me, and if im wrong in something please correct me. (Btw you do realize with the exception of what i mentioned about drilled being able to cool and explaining how- i agreed with a majority of what was said?)

Added: Someone said something about carbon brakes following a different set of rules and thats why they use drills, anyone care to explain the different rules?

DamonB

It's a rotor's JOB to hold heat. The less heat it is able to hold the less kinetic energy it can convert to braking force at the tire in a given amount of time. As soon as the rotor and pad material are above their heat range their coefficient of friction plummets and they become unable to convert kinetic energy into tire braking force. This is why when you get pad fade you can bend the brake pedal and the car still won't stop. If a rotor with less mass could do the job bigger brakes would not exist!

That's exactly what pad material does. If it didn't I wouldn't ever have to clean my wheels. Modern race pads use no metal in them but it wasn't too long ago that you could in fact see the glowing semi-metallic particles from the brake pads blowing down the side of the car at night.

You said "About the nascar and open wheeled indy carts/f1 vehicles (ando ther vehicles etc) using slotted over drilled, apples to oranges. Keep in mind these events are endurance events, why risk a rotor braking and handicaping you into the pits even longer when you could be out on the track? considering how hard these vehicles need to constantly be braking and the lower durability drilled rotors- endurance is critical".

NASCAR and CART races are only a couple hours long, they have no endurance events. If a rotor cannot even live a couple hours it's useless.

Why is there ever a need for a brake rotor with larger mass when you've already proven that a less massive rotor dissipates heat more quickly?

SidewaysGts

Well technicly speaking the rotors job is to turn the moving momentum of a car into energy, energy = heat (not to hold it, thats bad for the most part- u want to lose it as quickly as you can, generally ull never be able to lose it fast enough to hinder the cof). The quicker it can do that- the better. Thats why they have big brake kits- increase the rotor/caliper/pad size you increase the surface area and pressure at which you are capable of covnerting that momentum into heat.

Its actually a bit of both which is what i meant to imply, i should have had a "just" in there, so my apologies on that mix up.

Dont think of it as "a couple hours" think of it in terms of how much, and especialy how hard theyre being used. Take the speeds the cars theyre getting at, how much braking they need to do- how hard they need to do it- ur not giving the rotor a break to cool down, its continual hard stress and use. for a casual auto crosser or weekend warrior, you simply wont see the same kind of abuse.

Explained this earlier already- but as mentioned rotors turn momentum into heat thats how they slow the car down (Within the traction limits of the tires of couse, but thats how they do it). Increased rotor size means youve increased the surface area capable of converting that force into heat. Its not just the less mass which is beneficial- its the increased surface area.

Take my metal bar example from earlier and use two of equal mass but one with more surface area and your results will varry in which cools faster.

Added: Damn i really should check for typos -before- i hit send

DamonB

Look Ma, no holes!

A NASCAR rear rotor, a NASCAR front rotor and a Champcar front rotor from a Reynard. Pics taken by me

7racer

ha! you photoshoped the holes out

Smilodon

. No delete function.
so this is it.

7racer

I think you need to re-read this thread.

DamonB

HA! Even I have my limits on how much time and effort I'm willing to spend on changing the minds of some people

ptrhahn

iTrader: (9)

And you, of course, are tracking (road racing) this car regularly with track compound brake pads, right?

RETed

I think the better question would be...
Can you seriously take advantage of the...what? Maybe one pound less unspring weight per corner in your driving?
If not, why bother?


-Ted

MILOS7

iTrader: (3)

Bump

Specter328

iTrader: (2)

I know that the tripoint mazda 6 touring cars used drilled stoptech rotors and its a racecar, just thought I'd throw that in there

gracer7-rx7

iTrader: (16)

Why are you bumping this? Was there a point?

Its a good thread but there is nothing new to be shared on this topic that hasn't already been stated.

Atticus_

bringing this thead back to put in my 2 cents and to start another discussion.

FROM TIRE RACK's WEBSITE:


note that tire rack dosent recommend running performance brake pads on your drilled rotors for the fact they are not made to perform with them. they do not say anything about running performance pads on solid disk however.

I think this argument is pretty much settled, but im going to try and review and separate the fact from the opinion:


Cross drilled rotors DO in fact help dissipate gas buildup between the pad and rotor surface.

Cross drilled rotors are very susceptible to cracking when used in extreme conditions.

Cross drilling obviously reduces weight, so in extreme conditions is an advantage of reducing unsprung weight. (for anything other than a close restrictions race car is not a significant advantage.)


So in conclusion: Cross drilled rotors may look the part, but they will provide no greater performance increase over a common slotted rotor for the fact that they are too susceptible to cracking and therefor can't withstand actual racing conditions.



Now to open up another can of worms:

Slot direction. i know someone mentioned it, but it got quickly swept under the rug. you dont see much info on it, but i am here with an argument other than "which ever way looks better to you"

If you look at most of the pictures of slotted rotors from ALMS and nascar posted in this thread you will notice that they slots are made to face like this: \ with the front of the car being to the left <----- we all know that the rotor must be placed on the car with the directional vents facing the correct direction, but why are the slots always faced this way on most performance directionally vented rotors? (accept for Porsche of course but i think they can be set aside in this discussion dew to previous disputes in this thread.)

The vents are made to pull debris away from the caliper and out of the wheel, that is why they are directed towards the \ <----- front.

i will be back with more information on this but please feel free to discuss. please find any information you can on the subjects as it seems it is few and far between.

Atticus_

From Racing Brake:

anyone got any more fact that the slot should be directed in this fashion for performance?

Black91n/a

That sounds good, but it's not really a problem any more with modern brake pads.

It'll reduce the weight of the rotor by a very small amount, since you're really not removing much material when you add 50 or so 3/8" or what not holes. Do the math, it'll be something like less than half a pound. You'd be better off from a weight standpoint by turning the rotors down to half thickness or something like that.

Or, better yet, get 2 piece rotors with aluminum hats that can take whole pounds off each corner.

Install them so that the internal venting is facing "rearwards" as it turns so that it pumps the air properly (presuming they're directional). THAT is the proper way to do it, other than that I can't see that it really matters that much how the slots are angled.