MagnusB

Are there any?
I'm so tired of cracked rotors after 2 days of track use.

ivangene

Has anyone tried re-drilling new rotors with smoother holes and a better chamfer in an attempt to reduce propigation from the holes?

himself

I think there are a bunch of threads on this. There are very few options for the 996 fronts. PFC makes a 2-piece dimpled that last a long time. But the choices are few and none are as cheap as OEM.

Besides, a few little cracks don't hurt nothing.

-td

garrett376

what pads do you use that crack them in 2 days? PFC 97's per chance?

I've done 6 sprint races and 1 60min enduro, plus all the practice and qualifying for all of those races, and not a single crack using Cobalt Friction XR2 pads.

himself

Wow! I've gotten 1-2mm cracks in my OEM rotors in 1 DAY using Pagid RS-19s.

-td

Pac996

Yah there's advised measurements of the cracks for when to dump the rotors. I'm thinking part of the problem is temperature changes being the main culprit. To me it seems the ability of the rotors to cool so good causes the temp change to be fast enough to cause the cracks. Or maybe the rotors need to be warmed up before doing hard braking to help extend their life cycle.

Dervish

Without going to bigger calipers your only 2 choices are PFC and Girodisc. I went with Girodisc due to the size increase and weight reduction whilst keeping the standard 4 pots, the downside being the price...

LVDell

Magnus, what have you done to improve the brake cooling???

himself

There really isn't much you can do to the stock system in terms of cooling. Although what you can do does help tremendously. I did everything I could think of to improve cooling, short of custom duct work, including: adding GT3 air scoops (tried cup scoops but they were just too low), removed fender well for direct air pass through from front bumper, added GT3 internal air scoops to push air directly to rotor, ran endurance pads, upgraded to SRF. Ultimately, I upgraded to 2-piece solid+dimpled rotors. It feels like I tried everything except drive slow Nothing really reduced the time to cracking for my factory rotors. It was like the minute they smelled the track they cracked in fear...

I think DBA makes a set as well.

-td

LVDell

You contradict yourself You say you can't do anything yet you do???

The cup ducts alone help tremendously for me. If you don't like how low they are then just install them for track days as it only days 1 minute to attach them.

garrett376

You guys should try the Cobalt Friction pads - they wear out faster than Pagid Yellows or PFC97's, but rotors are unaffected - this is after various tracks: Cal Speedway, Buttonwillow, Willow Springs...

Pac996

That's short and sweat. Sounds like better pads for racing. I guess most want a street and track pad that wont wear as fast and will give them a year or so of use. They can't have everything I'd prefer those pads with stock rotors since they dump the heat with the pads particles wearing off.

LVDell

Sounds like the wrong friction coefficient for the application if the pads are wearing down fast and the rotors are unaffected.

garrett376

I don't know the answer to that, but after those events I listed, the pads are at 50-60% and the stock rotors have no cracks and little wear - car ran at 3400lbs for cal speedway, 3250 at Buttonwillow, and 3200 at Willow Springs on toyo RA1's/NittoNT01's. I never lost brakes even after standing on them frequently - cal speedway has a 130mph to 40mph entry to turn 3! It brakes with about the same feel as my 3200lb 964 race car with Pagid Yellows, but not near as much bite the 964 with PFC97's (but the PFC's cook the brake system too much even with BIG calipers on the 964 and crack the front and rear rotors after 1 event).

mglobe

DBA makes slotted rotors for the front. They are available at a reasonable price from TireRack. I haven't found slotted rears, so I use DBA on the front, and stock rotors on the rear. The rears don't seem to be as susceptible to cracking. This is on my race car, where I use PFC97 pads.