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hey guys, at yet another crossroads(ill be posting a fair amt on this forum area mainly due to the fact that now i have my engine up to decent standards, its time to get some stopping and cornering power) ANYWHO, now i know the general diffs btw drilled and slotted, drilled are better ventilated, but they do have a tendency to crack under heat, slotted have a little bit less heat reduction properties, but are stronger, but my big question is, whats best for my WRX? Now i know this depends on driving habits, on the weekdays, my accessport is set on fuel economy tune, on the weekends, its set on "smoke 35th anv SS's" tune, anyways, other than OCASIONALLY messing around with other cars on the hwy and at lights etc, the only real hard driving i do is at SCCA, once a month, and the runs are about ........ mmmm, normally under 2 mins, that at most, im leaning twoards drilled due to this, my brakes are never really put under stamina or long term diress, at least not until next season when i move up to club racing(going on actual tracks and wheel to wheel), but for right now......... needless to say im definately debating, because the set i want are the exact same price for drilled AND slotted, so price is no object, just wondering if anyones had experience with whats worked best with their cars(mines an 05), any help would be appreciated, and till next time, keep it easy big sleazy!
 

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I run DBA 4000 rotors all the way around, SS line, upgraded fluid and Hawk pads. This make the car stop much better.
If you are going club racing you will need a big brake upgrade in the front, and some type of ducting to keep the brakes cool.
 

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My personal preference is slotted. You need frequent and prolonged brake cycles to really need drilled IMHO. When I did calculations for a smaller, open wheel car brake setup even solid rotors had enough heat capacity and disappation for a racing circuit.
Drilled rotors can, as you said, crack but they can also warp before that if not of high enough quality. High quality ones usually don't experience this. If you decide to get drilled make sure the hole pattern is arranged so that the pads have constant surface area contact. Some manufacturers arrange their holes so the pad contact area oscillates and actually hurts performance. Brembo and the like do it right.
 

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Discussion Starter #4
Brembo is what i was looking at personally, like i said, their drilled AND slotted are both the same price from optionimports.com, so it wasnt price wise decision, in my previous car i ran drilled with hawk pads, im thinking of going for the carbonetic R-Spec pads, and as for the big brake upgrade, i wont need that for a little while, until summer at the very earliest(im only shooting for about 300-350 max whp, im talking MAX, and doing it on a 18g will be fairly easy, among other mods), now heres my question, will i NEED a big brake upgrade if im shooting for those amounts? Or could i get away with upgraded lines, fluid, pads and rotors? I mean the fade on the stock rotors so far has been nihl(ive run about 3 meets on them, and had no problems stopping at all), but whats the general consensus?(i mean, im dropping about 4-5 on the engine already, plus another G at least left on the suspension, so im trying to budget SOME, i mean i know you have to pay to play, but i was wondering if the big brake was necessary?)
 

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You never need drilled...not EVER

It is 100% a cosmetic mod.

Not a huge poster on here - but ask BigSky - he will vouch and agree.

-k
 

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You never need drilled...not EVER

It is 100% a cosmetic mod.

Not a huge poster on here - but ask BigSky - he will vouch and agree.

-k
not to discount bigsky, but porsche would disagree.

'course they, unlike many others, actually design their drilled rotors to ventillate heat and gas
 

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not to discount bigsky, but porsche would disagree.

'course they, unlike many others, actually design their drilled rotors to ventillate heat and gas
I have had this argument 100's of times.

Porsche (and BMW and Chevrolet and Mercedes) make drilled rotors for production cars because uninformed buyers think it does something.

It does not.

Watching the drilled front rotors on a C6Z06 crack in half as the car cooled down post track session is very interesting to say the least.



It is for looks - period. If you can find even 1 smidgeon of real data to contradict what I said I will send you a free set of WRX front drilled rotors barely used. You just pay for the shipping.


 

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I have had this argument 100's of times.

Porsche (and BMW and Chevrolet and Mercedes) make drilled rotors for production cars because uninformed buyers think it does something.

It does not.

Watching the drilled front rotors on a C6Z06 crack in half as the car cooled down post track session is very interesting to say the least.



It is for looks - period. If you can find even 1 smidgeon of real data to contradict what I said I will send you a free set of WRX front drilled rotors barely used. You just pay for the shipping.


That's cool. I used to work for a porsche dealership and had the opportunity to learn about their rotors. Been awhile, but I had an entire training course on them, granted just an online deal. The difference of one that works, according to Porsche who I am guessing knows more on the subject than you and I combined, is the internal ventillation of the rotor and how that is designed (or not designed) to scavenge the heat and gas which enters that part of the rotor through the drill holes.

Porsche says that most drilled rotors do nothing because once the gas enters the center of the "other guy's" rotors it doesn't get properly fanned out via the internal veins.

If you want to stop at a Porsche dealer the PCCB gen 2 brochure might show some information on this but I don't reacall. But if you've got some information that disproves specifically Porsche's drileld rotor design by all means post it up.
 

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Let's examine all the potential areas where cross drilling or slotting could help:
1. Gas buildup - The physics of it make sense but the actual braking performance may not be any different than solid rotors.
2. Water buildup - In very wet conditions where you're not using your brakes heavily, let's say taking an exit ramp after cruising on the highway without braking for while, they can help dissipate water and water vapor from the surface of the rotor. But like # 1, while the physics of it make sense, the actual braking performance may not be any different than solid rotors.
3. Heat dissipation - A well designed rotor can be solid and cool effectively, even in extreme conditions. A cheaper, poorly designed rotor may gain some cooling advantages via cross drilling or slotting.
4. Strength - A solid rotor is always going to be stronger than a slotted or cross drilled rotor of the same design/material/size. It's pretty simple, if you remove material you're going to weaken it. In a grained structure like steel, a slot or drill hole can create a path for a crack to form. With respect to all cross drilled or slotted rotors being prone to cracking, that's a total myth. Poorly designed, cheap ones are prone to this. Good ones are not. In racing conditions, even the good ones can have this happen though. One key thing with respect to strength is that good quality cross drilled rotors are cast that way, not actually drilled. Holes should NEVER be drilled in the rotor because it will have a large impact on the strength of the rotor because you've destroyed the grain structure. Casting them that way leaves the grain structure intact. Companies like Brembo cast the holes in there while the cheap made in China ones are probably actually drilled.
5. Cost - Cross drilling and slotting are generally more expensive than a solid counterpart for two reasons: 1) it's an extra step in the manufacturing process and 2) they're sexier and more desirable. In the case that the holes or slots are cast in, it's really more a case of #2.
6. Brake dust - Slotted rotors can help reduce or eliminate brake squeal by getting rid of brake dust on the pad surface. Cross drilled rotors will help do this too, but to a lesser extent.
7. Weight - A cross drilled or slotted rotor will always be lighter than the solid version of the same rotor because there's less material. Less unsprung weight is always good, but the small amount of material removed isn't going to make much difference. I would venture to say it's probably only a few ounces.

I vote for sticky. :)
 

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no......not again.... :)

I'm getting sucked in AGAIN :)

No doubt porsche drilled rotors are much better designed than most others.

They have alternating complete vanes and half vanes which hang down in the airstream. Good. I am sure the material is quite good as well.

And there are reliefs in the full vanes that allow for not drilling into the vane.

But.

The rotor is a pump - from inside to outside. The hole punctures the air channel - so I cannot see how this helps and it very likely hurts. I have not seen data that shows air going in or out through the hole. But it certainly will change how much air is sucked through the center of the rotor. Also - cast iron is brittle - so the cool(er) inner surface of the hole is contracting - while the nearby regions are expanding. That is why they crack.

Lastly - those holes fill up w/brake pad material once you start braking hard anyway - which would negate any benefit of the hole to begin with.

I have a customer w/ an 02 C2. He is tired of changing rotors after each track day. They are expensive.

There may be some very small benefit in wet weather - and machined rotors do help pads bite and increase brake torque some. But that can be achieved w/ slotting which has much less risk to failure.
 

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Power stop disagrees as do I. (photo taken by me at Sema 06 because of this ongoing argument on teh inta4rdw3bz and misinformation)



FTR I have owned both and tested both in the same size. Drilled stop faster and shorter period.

I endorse drilled rotors that are cast with the holes in them to eliminate stress concentration points.

Rotors that are "drilled by a MFG and not re-heat treated" will crack everytime as was the case when drilled rotors were first introduced.

And FYI Porsche doesn't do it just because people are stupid and it "looks better." Common man the "gov't conspiracy theory" mantra doesn't apply to everything.

My mind is made up, however I invite any one to scientifically and objectively test all three rotors of equivalent size and post the data.
 

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Arguably one of the best designed and engineered cars ever disagrees and feels cross drilled have merit to:



Lets not forget the most technologically advanced and engineered supercar introduced to date, aka the 253MPH monster, he disagrees and thinks drilled are better to:



Both pics taken by Me at SEMA
 

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and lets not forget those high performance machines where braking is a life and death operation, they agree with them ^^^^:

 

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bwahahahahaha

You FAIL!

PowerStop is a cheap **** chinese rotor with holes punched in it and cadmium or zinc plating to resist rust. I couldn't care LESS if you believe that or not.

Pure garbage - displayed at SEMA by nasty looking girls w/ fake boobs - and sold to fools.

There is no such thing as a cast in hole. If you had even 1 iota of cast iron tooling experience - you would know that.

:rotfl:
 

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Motorcycle rotors are typically made of STEEL - not iron.

Iron has excellent friction properties - steel does not. So they need holes to grab the pads. Some high end bike rotors are ductile iron - but very expensive and have other issues. Look it up in an engineering book if you like.

You can try any arguement you want - post any pic you want - and quote or cut and paste any nonsense you want. It does not matter because I am CORRECT and you are not.
 

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The rotor is a pump - from inside to outside. The hole punctures the air channel - so I cannot see how this helps and it very likely hurts. I have not seen data that shows air going in or out through the hole. But it certainly will change how much air is sucked through the center of the rotor. Also - cast iron is brittle - so the cool(er) inner surface of the hole is contracting - while the nearby regions are expanding. That is why they crack.
I vaugely remember at least some illustrations that showed the air moving through the different size veins. I tried just now to get on pcnasource.com and look but it seems my password has finally expired.

Has your C2 customer looked into the carbon brakes? It's probably $15K to buy them off the shelf, but a few Porsche driving instructors told us that the 2nd generation PCCB's are installed on all of their cars and had held up to thousands of track miles without so much as a dent in them.
 

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There is no such thing as a cast in hole. If you had even 1 iota of cast iron tooling experience - you would know that.
What are you saying? That's you can't cast a hole in a piece of cast iron? :confused:

The one thing lacking for me is any scientific evidence to back up the holes or slots making a difference. Like I said, the physics of it make sense but I'm not 100% convinced that it will stop you faster or cool better than the same rotor without the holes. FWIW though, I get sucked in by the looks of them like a lot of you so I'll continue to buy them. ;)
 

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No

I am saying if you try to cast that many little holes you will have serious mold flow and cooling issues and knit lines everywhere.

The only hole that is cast in to the rotor is the big one in the middle.

The ceramic brakes are often taken OFF the car once the cost of ownership is discovered. If you are Bill Gates though - yes they work great and save MUCH weight.
 

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I agree - the Porsche ones are quite lovely.

After the third or fourth set though they are not so lovely. They become quite ugly in fact when the rotors are otherwise new except for the hole filled with brake pad and the big cracks.
 

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Motorcycle rotors are typically made of STEEL - not iron.

Iron has excellent friction properties - steel does not. So they need holes to grab the pads. Some high end bike rotors are ductile iron - but very expensive and have other issues. Look it up in an engineering book if you like.

You can try any arguement you want - post any pic you want - and quote or cut and paste any nonsense you want. It does not matter because I am CORRECT and you are not.
I wasn't advocating "iron" vs "steel" rotors. I was advocating "cross drilled" vs "plain" or "slotted".

Facts about cross drilled, they cool better via cross flow. They reduce carbon smearing. They clean the pads of debris. They prevent fade by venting gases through the holes.

I have done extensive research on them, I have a degree in engineering and designed for my old colleges race team.

I suppose we'll have to agree to disagree, but a word of caution....please keep this discussion civil.

What are you saying? That's you can't cast a hole in a piece of cast iron? :confused:

The one thing lacking for me is any scientific evidence to back up the holes or slots making a difference. Like I said, the physics of it make sense but I'm not 100% convinced that it will stop you faster or cool better than the same rotor without the holes. FWIW though, I get sucked in by the looks of them like a lot of you so I'll continue to buy them. ;)

http://www.powerstop.com/content.wws?fname=technicaldata.html

Tons of graphs and Tech info there to which our dissenting member will dispell as lies. * shrug* supports my own testing results and conclusions.


As I originally said above, drilled holes are acceptable as long as the rotors are heat treated to accommodate and resist cracking. Those GARBAGE CHINESE POWERSTOP ROTORS carry a 3 year replacement warranty against cracking. I wish all grabage had that warranty.

cast rotors do exist.

http://www.movit.de/rahmen/frontbks.htm
click ..... all rotors sold by mov´it are cast rotors with cast holes.

http://www.movit-scandinavia.com/en/products_faq.asp
What is included in my kit?
Answer: Rotors with cast holes and ventilation slots, aluminium hats,calipers, brake pads, brackets, steel braided brake lines and bolts tomount the kit. The only thing that's not included is brake fluid.​





close up of a Porsche 993 RS rear rotor..the casting roughness is clearly seen in the holes



at the 911 (964) on only the Turbo had cast hole rotor´s
at the 911 (993) all models had cast hole rotor´s

The patent number on cast hole rotors is European Patent EP1472470
 
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