Thinking About Drilled Rotors?

[KTL]

Thinking about getting drilled rotors for your daily driver?

Think again.

http://www.ws6.com/cryo.htm

That doesn't look safe...........

Even the cryo-treated rotors are garbage. And not all that much abuse to them either.

I guess if the rotors aren't those with cast holes, why even bother if they're going to fail like these?

Granted, they're domestic rotors. I believe the brand are Baer racing discs.

[rattlsnak]

This doesn't happen with a factory rotor. Who knows what process the aftermarket companies use to drill the holes.

[widebody911]

#include [endless-discussion.h]

There's a diff between rotors with drilled holes and rotors with cast holes. The stock Porsche rotors-with-holes are cast that way. Some places drill them for max bling, but these are known to crack.

I'd have to see more evidence than one set of bling-drilled rotors before I'd cough up $100 to have mine stuck in the freezer. I'm sure it can't harm them, but it does appear to be a drain on the wallet.

[Calspeed]

Hello,

Drilled Rotors... from what I understand they are just a waste of $$$. You will not see any difference in performance over the solid rotors. Although they do look cooler.

If you look at any of the Indy cars or NASCAR rotors you will see that they are solid. I understand the concept of escaping gases and such. But from articles that I have read the drilled rotors do nothing more then look nice through a set of fancy wheels.

As for me... I may go with the vented ones. They look cool without the high possibility of cracking.

Calspeed

[widebody911]

Originally posted by Calspeed
If you look at any of the Indy cars or NASCAR rotors you will see that they are solid.

Using this logic, I guess I should also go out an pick up a pouch of Red Man, a styrofoam cooler, and a 12-pack of Bud.

Here's a gratuitous pic of one of TRG's cars - they seem to think drilled rotors are OK:

[Chuck Moreland]

Interesting. This guy is all happy with cryo treating because he got 15k street miles instead of 4k street miles on a set of rotors.

Should we tell him that rotors should last 100k miles on the street?

I'm not sure if cryo works, but I do know a sample size of 1 is not significant. Both of the rotors shown are way past the point of safe operation.

FYI, I've even had solid surface factory discs develop cracks.

[RallyJon]

The stock Porsche rotors-with-holes are cast that way.

But Porsche didn't ever equip 911s with cast holey rotors, and they don't make those rotors for 911s now, either, do they?

[Chuck Moreland]

Sure they did. The first were the old turbo brakes. Then 964 and 993.

[widebody911]

Originally posted by RallyJon
But Porsche didn't ever equip 911s with cast holey rotors, and they don't make those rotors for 911s now, either, do they?

Are you sure about this? The 930 rotors have cast holes, and later 911 variants do as well. Shortly after I bought my 911, I bought some Zimmerman rotors with cast holes.

[emcon5]

Originally posted by rattlsnak
This doesn't happen with a factory rotor. Who knows what process the aftermarket companies use to drill the holes.

Yeah is does, just not as fast.




The end-all discussion of cross-drilled rotors can be found in the infamous Altima Thread.

Tom

[KTL]

You know Tom (emcon5), I was thinking of that thread when I posted this topic!!!!

There is some serious flaming going on in that one....... and if I remember correctly, the flaming is well-deserved.

I agree that one sample is not a good way to judge the results of these rotors. But, you must agree that either 4,000 or 19,000 miles for a set of rotors is unacceptable. These rotors seem that they'd be a set of OE discs that were drilled. Just pure speculation on my part.

I do recall it being said many times that ALL perforated discs crack. Cast or not, it's just a matter of time. "Nots" just do it faster.

Hey, I know the NASCAR boys use the perforated discs at least once per year. The dreaded road course weekend.........

Wasn't the original purpose of opening up the faces of the disc to not only clean the pad of gases and pad material, but to evacuate water as well?

[RallyJon]

Post a part number for the cast-holes version of 911 351 041 20 and 901 352 041 14 and I'll order them tomorrow and bolt them on my '71. All I've seen are drilled Zimmermans.

[WERK I]

I do not undestand why the rotors in question were both drilled AND slotted.
(KTL provide the following link)
http://www.ws6.com/cryo.htm

Everything I have read on these techniques, one is similiar in function as the other. Why do both? I would think that doing both would compromise the structural integrity of the rotor.

Dave
85 Factory Slant (with new Zimmerman rotors)
78 911SC RoW

[Kmatts]

I recall seeing a picture of a Factory Ferrari 360 Modena race care a while back. Guess what it had on it for brakes? slotted solid rotors, no drilled or cast holes. just a thought. Kyle.

[Chuck Moreland]

Originally posted by WERK-I
I do not undestand why the rotors in question were both drilled AND slotted. Why do both?

It's for the coolness factor. And I don't mean temperature. Bling fokken bling, dude.

[Bill Verburg]

Any rotor will crack if abused enough. The factory w/ cast holes is just a little tougher than the drilled in this regard. The only 911 to use drilled rotors was the 911SC/RS which used the 930 rotors. There were no factory drilled 282.5x20 or 24. There are factory drilled 304x32, 309x28, 322x32, 322x28, 299x28 and 299x24 used on various 930, 965 and 993 models. Some were 2 piece some 1 piece. In general the newer ones are not useable on the older cars due to offset problems. The only exceptions are the 2 piece which can discard the newer o/s hats and replace them w/ zero o/s hats.

[masraum]

my understanding is all drilled/cast rotors will crack, just the cast last longer.

I think the escaping gases thing is pretty much a crock these days.

The only benefits that I see are decreased unsprung and rotational mass and increased surface area which is better for cooling. Race teams can use them because they inspect/replace their rotors much more often than we do.

Of course the benefit of solid is increased mass for heatsink and increased lifetime/durability.

Just my opinion.

[Bill Verburg]

Modern pads do not need the escape route for outgassing as much as the older pads. Weight saving is is real but minor. Bottom line there is no compelling reason for drilling(I'll continue to use them any way), cryo is a crock. Good metalurgy is the #1 thing to buy, stick w/ Brembo, Zimmerman, Alcon and you will be happy.

[911pcars]

"Race teams can use them because they inspect/replace their rotors much more often than we do. "

If some race cars use cross-ventilated rotors for the duration of a race (what, 24 hrs., an entire season?), what marketing scheme causes people to expect extended life (many, many thousands of miles) from a product that's inferior (drilled)?

Perhaps a case of misapplied race technology.

Sherwood Lee
http://members.rennlist.org/911pcars

[RXX7]

Just picked up a set of cross & slot BREMBOs for my RX7 which I plan on driving next month. I will be sure to document the entire process and post my findings! "Wish me good luck".