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Discussion summary
YOUR RESEARCHSlotted brake rotors for non-widebody cars?
Reported or suspected cause
temperature changes being the main culprit
Reported cause
No successful repair reported for this finding.
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Reported cause
I'm thinking part of the problem is temperature changes being the main culprit.
Leading evidence: 'temperature changes being the main culprit' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'temperature changes being the main culprit' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Install gt2 brake ducts up front' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
LVDell, I have installed the GT2 brake ducts up front to help with the cooling and use Motul RBF600.
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I haven't found slotted rears, so I use DBA on the front, and stock rotors on the rear.
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Suggestion
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.
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Suggestion
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.
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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
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.
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.
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...
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
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.
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...
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.
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).
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.
LVDell, I have installed the GT2 brake ducts up front to help with the cooling and use Motul RBF600.
I have Zimmerman standard rotors and Pagid Yellow pads.
Those rotors have worn down FAST! Almost one set of rotors for one set of pads.
Partsheaven now has Solid Slotted Non-Drilled Rotors front and rear for 996 c2 C4S and Turbo, Boxster S, Cayman S, [phone removed] ask for Al, Jeff or Spencer
I used Girodisc during last year's track season. Rotors still look new. I've been impressed with the performance over stock, no fade at all, very good pedal feel, very strong stops, although I'm certainly not the fastest guy out there. I will say that Girodisc plus RS19s is a pretty noisy combination.
I bought fronts and rears from Chris in January. Installed and ran at Road Atlanta last weekend. They are holding up just fine after three days. He ordered them from Sebro and, according to Chris, Sebro also manufactures the stock cross drilled rotors for Porsche. At $160 per corner, they are quite reasonable. Contact info for him is [phone removed]
[email removed]
and
www.merlinmfgusa.com
Was also tired of cracks on drilled after a few days of track. Bought front slotted from LC. They were mounted last week. Will try on the track next week.
FM
Alex/FM, thanks for your support and kind words. The slotted fronts and rears are a great alternative to the Alcon's (great option as well) we carry for the cost minded users.
Feel free to call or email with any questions.
Chris
What's wrong with a few cracks? I change my front OEM rotors maybe once a year and I race 2 series, total of 32 races per year. I have 3" ducting from the grill thru to the back of the rotors and I'm sure that's responsible for the longevity. And my weight (2600) is also contributory but still cracking is normal.
I do however have a set of Stoptech calipers and rotors for the front end of a 996 if anyone's interested.....
