Wow, I must have turned into a real bitch somewhere along the line- I need to work on that, I guess.

I don't care if you post prices, websites, pictures, whatever- as long as you don't work for or own the place you're talking up.
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Question for you guys who know so much about the drilled brake rotors. This weekend, I saw two new 911's, one turbo and one not. Both had drilled rotors. If they don't have any benefit, why did Porsche include them? They were also on the Viper and ZO6 we saw. And I'm not being sarcastic in any form, I just don't understand the concept here...

 

waiting for my rotors from project U, not only they have more brake power and better cooling, they are also much lighter which equals less unsprung weight!!!

 

compare the sizes of the vehicles to the relative sizes of the brakes: they're lighter cars outfitted with thicker, stronger, larger (dia. and width) rotors. but the biggest consideration is that they are not DRILLED, but CAST with holes already in them. rotors with holes cast in them (and have a structure designed around having perforations) do not run into the same structural problems as these "cross drilled" modified-OE rotors do.

RomanoM, where are you?? set the peoples straight.

 

No! No! I was just trying to stay within the rules, and wasn't sure what goes and what doesn't, exactly, so I decided to say less rather than too much (about prices).

As for the "wrath" comment, sorry, I guess my sarcasm wasn't clear.
Great, thanks for clarifying!

 

True. There is a grain pattern that flows with the shape of a casting. If a solid piece is machined, it cuts through and distrupts the grain. It's is complicated by the fact that the impact of the cutting tools will most likely distrupt the hardening of the surface [.001"] if it is not annealed first. That doesn't sound like much, but the the slight change in metalurgical properties gets ugly during the constant heat cycling of a rotor. Then you will see cracks at the holes going outward. The rotor is probably not going to fall apart anytime soon with street driving, but if your only street driving there is VERY little benifit to drilling your rotors other than getting the Porche look.

I work on and with 911's alot. Even the super pricey cast-drilled rotors crack [under race conditions]. It's a balance of performance and reliability. The Porche crowd presumably has better cash-flow than the RX-8 crowd to allow more frequent replacements.

I drive my 8 HARD all the time. Not once have I been braking sooo hard long enough to have significant [or even noticeable] brake fade.

 

might want to also consider that most drilled and slotted rotors are also freaking huge so they make up for any loss in surface area.

 

unless you can fade your stock brakes......which i would find pretty hard to do with even fairly aggressive street driving, you should keep them stock.

rotor upgrades would probably come with upgraded pads. higher friction pads make more heat, cross drilled or slotted rotors disappate that heat faster. if you are track/autox enthusiast, upgraded brakes are probably a good investment. if not, proally not worth the cash.

 

On my third track day I started to over heat the brakes and ended up with a mushy brake pedal. Bleeding the brakes restored pedal feel but the pads/rotors feel a little glazed.

In defense of the stock setup I have to say that they put up with the high speed abuse of Watkins Glen admirably and they are just coming up a hair short.

So now I'm looking for ways to make the brake system more robust. I think that I'll start my mods with higher temp brake fluid and pads. If that doesn't do the trick the next step IMHO would be larger slotted rotors.

 

tell me how your brake system upgrades go for you. if i decided to track my car, id also probably opt for the same upgrades as you.

if you were in california speed racer, id want to go tracking with you. ive never gone to actually driven at a track before, but ive been to buttonwillow twice to spectate.

maybe ill go to seca sometime this year if i can get some extra money and time off school and work.

 

i read somewhere that the slots and holes act to allow gases whic evaporate from the pads to evacuate. it said that these gases noramally get trapped between the pads and rotors causing braking problems. basically it was said that the slots and holes act sort of like the tread on tire, which allow the fluid to escape giving better traction, or in this case braking force.

 

Yup, that was true - 30 years ago! However, modern brake pad compositions no longer have the problems with outgassing when green or when hot that brake pad materials from 20+ years ago did.

Modern brake pads no longer need the holes, but the drilled rotor style caught on - and that's all it is, a style with no performance benefit. Porsche and Ferrari fit them on their top models because their marketing departments tell them that the customers insist on them because of the high-performance image, not because the engineering department says they need them!

Regards,
Gordon

 

thanks gordon for straightening me out on that. and for the rest of it i think you've got it dead on there. all marketing.

 

This is the first post on this thread that I totally believe. It nicely summarizes my thinking.

 

well there is a slight benefit of slotted rotors with newer pads in that the slots usaually clean the surface of the pad up, especially if you had them hot and glazed over from track use you wouldn't notice a problem.

 

Anybody knows the thickness and diameter of the stock brakes rotors?
thanks

 

Damn 800 bucks for crossdrilled and slotted? That is pretty steep. I think their cool and all but more like 400-500 seems reasonable for stock rotors drilled/slotted.

 

what'm i, chopped liver??

 

I'm totally on board with the idea that slotting and drilling is of minimal value in this day and age, but I don't know about machining effecting the grain structure of the alloy all that much.

You guys do know how small the grain boundaries are right? It's not like the grain in wood - it's waaaay smaller, and unless there's localized heating associated with machining, I don't see how it effects the grain structure. In fact, I would guess that when they crack it's due to stess localizing around the changed geometry - not so much a materials issue, but it would have more to do with the mechanics of the solid. I might dig up the book afterwhile, but I can't see how you're really effecting the grain structure by drilling the holes if you keep your process in check.