This isn't Evo specific, but at the last DE a guy with a Camaro (he's young and misguided, but otherwise OK!) had drilled rotors and at the end was complaining that his brakes felt funny. After the last session we were looking at them I noticed at almost every hole in the fronts a hairline, surface crack about 1/4" long, perfectly straight and radially inward. I don't think they had anything to do with the problem he was having but I was wondering if that's the typical fate of drilled rotors and how serious that is at that point.

Dave

P.S.
Emre, how are your friend's rotors and hats coming? And weren't you just taking boards?

 

All cross-drilled rotors will crack.

 

It's pretty common, actually. That's the major downside of x-drilled rotors: they weigh a bit less but they're prone to sudden failure.


They're done, but I've been too busy to fit them to the car. I'm taking my boards this Sat and Sun...so I'm a little preoccupied!

Emre

 

^^^ what he said, slotted are better but supposedly eat through brakes quickly ...

 

That's a fact! I tried slotted rotors exactly ONCE on the track: they wore out a brand new set of race pads in a single day (4 sessions). With regular rotors, I was getting several weekends out of a set of race pads and the stopping power wasn't any worse.

As far as I'm concerned, plain rotors are still best for hard track use. I've never seen any noticable improvement with x-drilled or slotted to justify the hassles.

Emre

 

I don't like that "sudden" part! I was surprised at how uniform the cracks were. That, and the fact that they seemed, by eye, for what that's worth, to be just surface cracks almost had me think they were an artifact of the manufacturing. But there were none on the rears and not at every drilling on the fronts so I'm sure they arose during use.

I'm looking forward to your review. Good luck, and does this mean you're moving south of the border?

Dave

 

well that sucks, I wasn't aware of extra wear on the pads with slotted rotors before I changed mine out. I suppose I'll see how it treats me this year

 

Hi, Dave,

Yes, it looks like I'll be in Boston next year. I was offered a position at Mass. General Hospital/Harvard Medical School. Looks like I'll be doing a lot more events at NHIS with the BMW CCA--Boston Chapter next season!

Emre

 

Track Junkie? Auto-x fiend? Rally/Rally-x nut?

Check the upcoming schedules: http://www.racenewengland.com

--kC

 

I noticed most manufacturers who make drilled rotors say that the drilled versions are not meant for track use...

 

The "sudden" part is the part that sucks. A few years ago the street racing scen was huge in Seattle and there were a few crashes resulting in fatalaties- at least two were blamed on drilled rotors failing.

In a nutshell, the rotors get hot quickly and then cool quickly because they're not under constant use. This quick heating and cooling causes stress fractures (the sharp edges around the holes are called stress risers and are heat sinks that contribute to fractures). Take a metal file and drop it. now take a propane torch, heat it to bright red hot and drop it in a tub of water. Now drop the file on the floor again, or try to give it a tap with a hammer. Chances are, it'll snap- that's sudden failure from fast cooling.

 

I will second that with experience. Blanks only for me thank you. I can't afford a new set of $210+ pads every track day.

 

I agree with this. Cant go wrong with solid rotors.

Although right now I am using the RRE 2 piece rotors. They are dimpled, not drilled all the way through, and have held up real well through 3 track weekends so far....pads look good too. We'll see how they hold up next weekend with more HP in the car.

n

 

I have been reading this thread with interest.

I have heard that (I forget where I read it) that drilled rotor that were forged with the holes in place do not suffer this cracking problem. It's the drilling of the holes that causes the potential for cracking...

Anyway, that's what I have read, but can't find the link anymore.

I use slotted rotors for now, so far my pad wear has been acceptable, but I don't subject my EVO to the rigors of a race track (yet)...

 

The porsche style have dimples countersunk into the crossdrilling. This smooths out the area where heat will buildup and reduces cracking dramatically.