Dang Nasti

Cross Drilled has nothing to do with dissipating heat. In fact.. some cross drilled actually loses it's ability to hold heat before it gets heat soaked (max amt of heat it's able to hold).

In order to DISSIPATE heat better. Your rotors need maximum surface area. drilled and slotted may increase surface area slightly, but not by much...

by drilling and slotting.. you lose rotor mass.. which is critical for your rotor to hold heat before it it becomes heat soaked and loses it's ability to to stop well.

The main purpose of drilled and slotted rotors is to release the gas bubbles that are trapped in between the pads and the rotors. which is only a major problem with track use (autocross).

The best way to solve heat problem is to get bigger rotors for better surface area and mass... if you get a solid rotor it'll hold heat better and will less likely to get heat soaked. If you get vented rotors it'll cool off better.

If you have comments.. be nice.. this is my first post.

Imolavirus@BuehnEngineering

try imolavirus@gmail.com if you get a chance

ryans4

...but in terms of the fundamental point of a rotor, which is to absorb the heat that was once motion, having holes instead of metal would be a detriment to that end.

But like anything, it's not so black and white. For example, say you put on some 355 rotors on a Lotus Elise. Given the hp and weight of that car, those 355s will likely last a long time, even in track use. So why not save weight (marginal) and get better pad "grip" by going cross drilled.

A rotor will eventually crack, whether it's drilled, cast w/ holes, slotted or nothing.

Most race cars run a slotted front disc. I've not seen cross drilled front rotors in many Touring Cars (plenty of cross drilled rears in FWD TCs). And once you got to the serious GT cars that can't run carbon setups, they are all running massive iron slotted discs.

With teh advent of segmentted slotting and non traditional slot style, they are blurring the line between the pad hating cross drilled discs and the more pad friendly slotted discs.

I think slotting/cross drilling does evacuate gas build-up between disc and pad, but the primary benefit is the abrasive action against the pad surface, which keeps grip up.

For example, check out Alcon's crescent slots, they are basically half holes:
<img src="http://pictureposter.audiworld.com/4359/252_vented_disc.jpg">

So in my opinion, the benefit of cross drilled is their aggressive action against the pad more then anything else.

[badmoon]

Sent to gmail.

Imolavirus@BuehnEngineering

good info.....thanks

B5QShip

you are teh smahrt =)

ryans4

...there are really 3 ways to cool a rotor better assuming it's already a directionally vented rotor. Increase teh air gap, increase the diameter and/or force cool air onto it (ducting/fans/etc.). And as for teh air part, the ideal situation would be to force air into the center of the disc and have it work through teh vanes. But with a drive axel in teh way, that gets tricky.

The air gap is teh width of the center vaned portion of the disc, not the side "plates" that absorb the energy.

An increase in diameter makes the rotors job easier, but the penalty is in the rotational moment of inertia which costs you more power to spin a larger diameter object when it's mass is not centered (which a rotor is not).

The "perfect" solution is some mix of all this crap based on the weight, hp/tq and desired use of the car.

Imolavirus@BuehnEngineering

is it ideal to direct air straight onto the back side of the rotor? Or should it somehow be directed to the internal vanes?

From your post it sounds like idealing having the air directed to the vanes would be best....but is there anyway to do that?

Hal_TT::CBP

Lost me... have to get the manis out yet. Going out tomorrow when UPS opens.

Imolavirus@BuehnEngineering

Is FedEx closed too? eek....didn't realize that