jhbrennan

Porsche or aftermarket?

Alexandrius

Two things I would like to adress;

I drove on small "spider" cracked rotors for something like 10 DEs with absolutely zero issue. What a Porsche racing shop told me; "stock rotors are great just be careful once you have massive cracks that connect..."

I have a feeling people are seeing small cracks and panicking.

As for the drilled holes, they do serve a practical purpose. When changing rotors, the holes signify the direction the rotor should be installed. The holes mirror what your vanes do inside the split rotor...

Hence the rear rotor has evenly dispersed holes with no diagonal pattern...the vanes are also straight and non directional.

On the front rotors, the holes are in a \ curve and should be installed that way as it is the correct way to ensure cool air coming in flows through the vanes on the split rotor.

So they do serve a practical purpose.

I think people are overblowing the spider cracks.

MaximumA

Interesting. I always thought that rotors were drilled to reduce (unsprung) weight... and I have to admit that I was a bit concerned when I first saw the holes on the 997, as I've always run plain discs on a road car, or slotted - with uprated pads! - on a track car. Let's see how it goes in a month or so, when I finally venture out on to the track with the 997 for the first time.

177mph

Lots of opinions on this thread.

I wish every rennlist thread came with an engineer and a chief mechanic from a 911 race team.

Then we could just get to the answer quickly.

Alexandrius

I mean it's a fact...we have split rotors.

Fact: slotted, which has higher ability to stop car on track due to friction, will also eat stock street pads alive.

Fact: Porsche had to decide if they wanted to thus go plain slick sided rotors, or drill holes.

My opinion: They drilled holes...for looks and various other factors. Most factors were for convenience. Holes allow for adding of wear "dimples". They also allow the user to see the orientation of the rotor on the hub while being installed as you can see the direction of the vanes (located in the middle of the rotor) and make sure to install the right rotor in the right place.

Another opinion; preety sure not a single complaint of the Porsche 997.2 is out of the box, on track braking performance compared to other cars. Which leads me to believe those complaining about cracks are probably complaining about encountering extremely small spider cracks (which I've been told by experienced pca racers and a race shop mean zero). These rotors are quite thick and the spider cracks I saw (which didn't occur until the rotors were @ minimum thickness anyways) were extremely thin and small. I asked my race shop about it and they said I could run it for tons more track days.

lowbee

I always feel I have better initial bite with drilled rotor on a rainy day than a plain rotor....so I am sticking with OEM drilled....

Racetwin2

I agree - drilled rotors is probably the best way to go for the average Joe tracking it once or twice per year.

Under day to day use the holes serve a purpose also for removing water when driving daily. You gain very important meters reaction time when brakes are cold and rotors covered with water.

Also Improves cooling somewhat etc.

Actually - holes can also prevent cracks from spreading. Cracks will always appear where there is highest stress on the material or the material is weak (imperfections, impurities etc) so if it spreads from one hole to the other it might actually stop and not spread further.

996SPECticle

I believe I caught the reasoning given by a Porsche engineer maybe 15+ years ago, I want to say that J Leno asked the question as to why the holes in modern street rotors=pure aesthetics=Factory posery, same reason Ford put red calipers on an Explorer Sportrax

Now Cryo frozen rotors is some marketing hype I can get behind

scorcherjf

Been through a couple sets of the OEM drilled rotors. They develop spider cracks pretty quickly as others have said. I think after only a couple track days they start showing up. The rotors end up lasting a good 10 track days or so before the cracks get big enough to cause alarm (this is with PFC08/PFC11 pads).

Eventually switched to Girodisc slotted all around and they're wearing MUCH better with the same pads. Have over 10 days on them and they still look almost new. Some very slight hairline stress cracks showing up, but nothing that you could feel with a fingernail like the OEM rotors. I think they'll easily last 3x as long as the OEM ones.

nwGTS

Food for thought from August's Excellence:



Lower first column...
weight savings
Better cooling
Water evacuation

I suppose slotted would handle the third benefit but not the first two.

Tom Feldmann

I've seen a few manufacturers go with a combination drilled and slotted rotor recently (example).

I was curious how these would perform so I threw a set (Power Stop Track Day) on my Challenger for a track day in October...alas I ended up buying my .1 C2S so I'll probably never get to test them out unless I take the beast out to wax nostalgic
Going to the track with the stock rotors in 2 weeks...we'll see how they do.

TrackDays247.com

The original picture still of the video, at the beginning of the post - the rotor on the left has HUGE holes...and close to the edges..

3Series

Those ECS Tuning 2 piece rotors look very cool.... If I recall correctly, $900 is pretty cheap compared to Giro Discs. How much are replacements?

My opinion is that 2 piece rotors are not worth the price premium unless someone else is footing the bill. The stock 997 S brake rotors and calipers are perfectly fine for any DE or Club race.