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Old 11-17-2005, 10:44 AM   #1
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Default WHY Blank rotors are better than cross drilled and/or slotted

<<I'm posting this here too as well as the Tech. Misc. Forum because this really affects people in here the most and I care about your safety because I have seen too many people get hurt by negatively affecting their car via modification and I feel braking is a VERY important system for this.>>

http://honda-tech.com/zerothread?id=1437507

Ok I'm hearing a lot of conjecture, and people are STILL blowing money on shitty rotors, so I will tell you all why blank rotors are better.

The reason for the creation of cross drilled rotors initially was to remove the "gasses" from the brake pads. HOWEVER, most of your modern brake pads (Axxis metal, AEM semi-ceramic) do NOT produce gasses when heating. This was on bad brake pads used in the 1950s and 1960s. Back then, asbestos was also used, and we dont use that either.

The other reason is so called heat dissapation. I don't have my physics and thermo books with me, but the logic is that the holes in the rotor are suppose to allow the brake pad to cool. So...air gets into the rotor from the inside of the vents. If you have a back rotor which is solid, air gets into these holes how? If your stopped, you are leaving air inside these holes sandwiched between the pads, thus creating air with a rising temperature. Its increasing in pressure from the heat, which I guess you "could" call a gas that would affect braking. So the cross drilled rotors do not remove any gasses formed by brake pads (because there are none created anymore) but could possibly inhibit the creation of "hot spots".

Cross drilled rotors have LESS contact area because of the holes.
But if the rotor is cooler, its better, right? Well no, because these rotors are not cooler. THe heat is generated from the pad/rotor contact. What removes heat the most effectively? When stopped or moving, the pad transfers heat into the rotor because its made of cast iron. the rotor has a lot of surface area and even vanes in it. But the little holes allow air in this surface contact, and you can transfer more heat into a solid big *** chunk of cast iron more than you can into the air. Don't believe me? Touch some steam at 150 degrees, then touch a piece of hot metal which is at 150 degrees. Which burns your hand? the metal. So let the heat transfer into the metal, because since it has so much more surface area, dissapates better.

Safety!!
Cross drilled rotors can crack! I have seen them!!


Even racing teams will reccomend AGAINST cross drilled rotors:
http://www.livermoreperformanc....html


Companies that sell cross drilled rotors that are redrilled may not be structurally sound. I have actually seen pictures of rear Integra rotors that have had hairline cracks turn into the rotor actually breaking apart!

Do your homework. Even Porsche and Ferrari will admit that the cross drilled rotors they use are for looks. So if you are one of those kids who thinks the little holes look cool, get a name brand drilled rotor like Ferrari does. The REASON Ferrari's 'holed' rotors are alright to use is because they are CAST with the holes in them, so they are not actually drilled into cast iron rotors. Cheap drilled rotors are not safe, and even the good ones are not necessary. Why do Ferrari do it? People THINK they want it, and it sells. If you don't believe me, go into the business world. You will learn that pretty soon, you can sell utter **** if people THINK its better.

Information I gathered from http://www.pdm-racing.com/prod....html
says:


"KVR Crossdrilled Rotors

Why should you upgrade to cross drilled rotors?

Simply stated, the function of any vehicles brake system is to stop the vehicle. This is accomplished by absorbing the kinetic energy stored in the moving vehicle, and converting it into heat. The friction caused by the brake pad rubbing on the rotor is the source of this heat. The more quickly and efficiently that heat can be absorbed and dissipated, the more quickly and efficiently the car will stop.

There are several contributing factors to this heat reduction. One of the most common sources of heat is from the gases produced by the bonding agents of the brake pad burning off. Under severe braking, this can actually produce a boundary layer of gas that pushes the pad away from the rotor, which can lead to excessive brake fade. The cross-drilled holes or slots in a rotor provide an escape path for these gasses (de-gassing or out-gassing are common terms), and allow the pad to stay in contact with the rotor. As well as de-gassing, cross drilling or slotting will provide better wet weather braking as water is swept through the holes, or down the slots.

A vented rotor can be viewed as an air fan. When in motion, the vents draw air from the center of the rotor outward. This air flow, over an increased internal surface area, effectively dissipates rotor heat. Cross drilling adds to this air flow, as well as providing additional rotor surface cooling. "

This company is just telling you that the rotors may be cooler, however they fail to mention that the holes really do create a more than substantial decrease in surface area, thus less braking, thus less heat created, thus the less heat CREATED will leave the rotors cooler, the holes barely do anything! Its the less braking lowering the temperature!

Slotted rotors-
Find me a company that uses stock slotted rotors. They remove brake dust, but if you study braking systems, you find that with modern cars, flat blank rotors and semi-ceramic pads, the brake dust causing the rotor to slip on it is almost non-existent. But the brake dust doesnt need all those lines. Notice how most front brake pads (and most back) have that line down the middle to give essentially two bite points. If OEM or racing companies found it to be a benefit, they would do it.

PROOF OF IT ALL:

Find me an F1 car as of now that uses cross drilled or slotted rotors.
They all use full ceramic rotors and ceramic pads. Are they drilled or slotted? No.

If they helped the fastest cars in the world, wouldn't they use them? Its basic calculations that show the lack in surface area does not make up for the possible loss in temperarure. They use brake cooling air ducts insted.

BIG BRAKE KITS:
Some have asked if the big brake kits are worth it. This is sort of a relative question, but the simple answer is no. Regarding the big ones with drilled rotors, if you know that they are cast that way, at least they wont crack. I will still advice against them.
In terms of a big brake kit, I have seen some for Civic DX models. Civics have the small pad, small caliper, and a 9.5" rotor. The big rotors are 12" in diameter, ok so the overall diameter is close to that of an Acura RL (1999). But the sweeping area (the area that the pad can grab) is still the same if they use the same caliper and same pad. If you have the same pad and caliper, you are using the same rotor surface, just farther out, so it will increase braking from stock. However, if you were to change knuckles, etc, and get Acura RL caliper (larger piston than your civic DX piston), RL pads (much bigger and taller), and RL rotors 11.8" but much more surface area is touched, then you have a better brake setup because you have OEM parts, and a better grip on more area of the rotor. The downfall is added weight (since big brake kits are usually 2 piece and lighter) but the benefit is that you have so much more stopping. Ok, so the big brake kit will have less unsprung and rotational mass (so a little better accelleration but less braking), but they tend to run over a grand, and you can use OEM parts to build a better setup for half that.

IN CONCLUSION:
Don't buy slotted or cross drilled rotors, blank are better, and stop better. Physics people, get me my formulas and help me out here.

If you must get rotors with designs on them, get the slotted ones by a good company, and DON'T get blank rotors redrilled with little holes all over them. IF you absolutly must have the rotors with holes cause you like em, get them from a company that casts the rotors like that. I have seen rotors break and this is for your safety!

REMEMBER......
Your car will only stop as fast as your tires will allow. All the braking in the world wont work if your tires are bald and on ice!!


Modified by Redline96LX at 6:42 PM 11/17/2005
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Old 11-17-2005, 10:51 AM   #2
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (Redline96LX)

Good read, I was actually just researching this earlier today.

So what's the difference between say Brembo blanks and the stock rotors? Since blanks are better are stock blanks and pads ok to stick with unless you've got some serious **** to stop?
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Old 11-17-2005, 10:52 AM   #3
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (Redline96LX)

nice write up i'll keep it in mind
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Old 11-17-2005, 10:53 AM   #4
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (Redline96LX)

Thank you, very informative.
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Old 11-17-2005, 10:53 AM   #5
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (Redline96LX)

Good info dude thanks. I have seen some cross drilled rotors crack myself. Its shity that they would even sell something that dangerous that is that vital to the safety of the vehicle. Cross drilled rotors
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Old 11-17-2005, 10:59 AM   #6
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (******)

blanks are just the flat, cast iron rotors. I know brembo makes good ones, there pretty much the same as OEM but cheaper, cause you can get a set for under 100$ and the dealer will rape you on cost.
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Old 11-17-2005, 10:59 AM   #7
 
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (b33r-ninj4)

this has been an arguement at my shop for 2 months now.
i thank you kind sir.
you have just helped to further prove my point.
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Old 11-17-2005, 11:03 AM   #8
 
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good post, enough with the ricer **** already, use what works and is proven to work. brakes, suspension and tires are areas that are not to be fucked with.

a good pad such as Hawk HP plus, Brembo blanks and a good brand name stainless steel line is all thats needed for a good brake system.
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Old 11-17-2005, 11:05 AM   #9
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (Redline96LX)

Quote:
Originally Posted by Redline96LX
blanks are just the flat, cast iron rotors. I know brembo makes good ones, there pretty much the same as OEM but cheaper, cause you can get a set for under 100$ and the dealer will rape you on cost.
Reason I ask is I have a set of OEM blanks in the attic. Haven't been on the car for about 3 years, but I'm thinking of switching back to them. Having them resurfaced/turned and then getting new pads.

What kind of break-in, if any, do OEM rotors and pads need? Seems like I have seen that they really don't.

Sorry to hijack, you just seem like you know your ****.
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Old 11-17-2005, 11:09 AM   #10
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (******)

Brake Brake in:

With new pads and rotors:
Get your car up to about 40mph, and hit the brake lightly, like you can feel it gliding along the rotor, untill the car gets to about 10mph. Don't get it to 0. Then get the car back upto 50mph, hit the brake a little firmer, and get the speed down to 10, again, down to 10mph but not stopping. Then get the car to 60, and hit the brakes firmly (not hard) and down to 10. Repeat this procedure once more and they should have seated nicely. If for any reason your pads expletive up or get **** on them or dont seat right, take the pads off, hit the pads and rotor with some 400 grit sandpaper, and do this again. After this, thats all you really need, but many will reccomend you don't do any "Hard" braking for the first 200 miles of a brake pad, tho with modern brake pads, its not that big of a deal.

P.S. I learned that at 95mph, Anything is hard braking, when I was failing to chase a Porsche Carrera GT2.
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Old 11-17-2005, 11:10 AM   #11
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Brilliant
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Old 11-17-2005, 11:28 AM   #12
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Default Re: (Archidictus)

Thanks for this post. I argue with friends all the time about why blank rotors are better. This should be put into the FAQ's section. I have seen threads about cross drilled and slotted rotors being better, blah blah. Good post.
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Old 11-17-2005, 11:51 AM   #13
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Quote:
Originally Posted by green00EX
Thanks for this post. I argue with friends all the time about why blank rotors are better. This should be put into the FAQ's section. I have seen threads about cross drilled and slotted rotors being better, blah blah. Good post.
I road race and I use Brembo Blanks . Freaking nice rotors for the cost. Never warped in all the abuse I've put through them.
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Old 11-17-2005, 11:52 AM   #14
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just wondering, but why do all high end companies do slotting or cross drilling? Just for looks?
I always felt they could do it since their rotor sizes were so large they could do it for athetic appeal
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Old 11-17-2005, 11:59 AM   #15
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (Redline96LX)

Nice write up, thanks
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Old 11-17-2005, 12:02 PM   #16
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I saw a write up on this in a magazine last year. Called burnishing I think. They said the mechanics are supposed to acutally use a thermo device at the shop the heat up the brakes to exact specs in the SAE manual and keep it there for so long. The other method is a 30-30-30. 30 MPH hit the brakes firmly not hard come to a stop are start going again wait 30 seconds and do it again. Do this 30 times and it should be done. I did this to my last CRX but I didn't get to 30 times I did it about 15 and good enough. My CRX DX stopped better than my HF that had Integra brakes on it and the rotors never warped and I'm very hard on brakes coming through the mountains. Previous I've had rotor problems on my integra, crx HF with stock and with integra brakes. So I would definately recomend doing this on new brakes.
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Old 11-17-2005, 12:03 PM   #17
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Default Re: (igo4bmx)

Quote:
Originally Posted by igo4bmx
just wondering, but why do all high end companies do slotting or cross drilling? Just for looks?
I always felt they could do it since their rotor sizes were so large they could do it for athetic appeal
i watch jgtc racing all the time and a lot of there cars have slotted brakes ..guess sombody better let those name brand companies know that thats rice and they really dont work brembo cough: cough:
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Old 11-17-2005, 12:06 PM   #18
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (Redline96LX)

REPOST

I think this should be a sticky since you have to read a 5 page argument to get all this info. Good write up
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Old 11-17-2005, 12:11 PM   #19
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (fasthatchb18c1)

Good post
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Old 11-17-2005, 12:32 PM   #20
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Default Re: WHY Blank rotors are better than cross drilled and/or slotted (spoonracer84eg)

WOW! Nice write up, you just saved me money by switching over to blank style rotors! haha. So if I get the Brembo blanks with Hawk HP Plus pads and some good brake fluid, Ill have a decent brake setup on my ek hatch?

Also in your post, are you saying to stay clear of slotted rotors also? Basically am I better off buying the blank Brembos of say a powerslot rotor or slotted brembo rotor?


Modified by the twanksta at 1:45 PM 11/17/2005
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Old 11-17-2005, 12:34 PM   #21
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Remember that if a company that makes slotted or cross drilled rotors, and sponsors a car, do you think that car is gonna use their parts? Id think so
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Old 11-17-2005, 12:46 PM   #22
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Default Re: (Redline96LX)

so are the slotted rotors that aem and brembo that are good companies any good will they crack too. just wondering
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Old 11-17-2005, 12:52 PM   #23
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cross drilled are good in some situations. i don't see why a road car would have them, but **** like my atv has cross drilled rotors. the holes work very effectively in allowing area for mud n **** to get off of the braking surface.

but for car's it is stupid. but their good in some situations
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Old 11-17-2005, 12:55 PM   #24
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With Brembo blanks the whole rotor doesnt rust, like with normal OEM rotors the inside vented area would rust. Thats what I heard, i could be wrong. Input would be nice.
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Old 11-17-2005, 12:56 PM   #25
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Quote:
Originally Posted by Archidictus

I road race and I use Brembo Blanks . Freaking nice rotors for the cost. Never warped in all the abuse I've put through them.
Damn straight; same here.

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