Jack

This report also seems to provide additional data that suggests the stock brake cooling setup will not provide adequate cooling for steel (or ceramic) rotors under extensive track use conditions. For a more complete report on Martin's track experience, check out this VIR thread. If this is old news, I apologize in advance for wasting band width.


QUOTE: -------------------------------------------------------------------------------------
"Day Three VIR Update: The car now has nearly 1800 miles on the odometer. 1000 break-in miles and 794 track miles. Front rotors are now showing tiny cracks up to 1/4" long around the cooling holes. Engine is extremely strong and oil consumption has been minimal with the gauge down only one notch.
The GT3 sounds great from inside the car, especially in the 6500-8200 RPM range but is still very quiet relative to older air-cooled Porsches and the 996 Cup cars. I'll be looking to get the Fabspeed muffler bypass exhaust pipes on the car for next spring so the engine noise is not drowned out when near a Cup car or other race cars on the track.
The suspension could be stiffer, although the car was still able to pull 1.28 G's lateral acceleration with the OEM tires, according to the Data Logger. Pretty amazing stuff from a street car.
The windshield does not hold up well to getting hit by tire marbles and small stones. I've already got a 3/8" crack and too many small pinhole marks to mention. German windshields, I'm told, are softer than those produced in North America. Three track days seems to confirm this.

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Martin

PCA DE Instructor
2004 Slate Grey GT3 "
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Dirt Track Racer

Just read it and have a few questions for that PCA instructor.

1. What type of data logger is registering 1.28g and is that steady state or a spike? Big difference. I believe a GT3 on street tires will require about 1500 lbs of downforce to see that kind of grip steady state.

2. I don't see any mention of brake cooling being a problem. In fact, in an earlier post he says it was going to be 35 degrees the next day. Smart guys sometimes even tape closed their ducts when its that cold to keep from destroying a rotor. I will hold judgement until I see an actual picture of the offending cracks in the offending rotor. My 993 and any other 911 I have ever seen (GT3 included) with crossdrilled rotors develops small cracks very quickly.

3. Lets all complain about the soft windshield in our cars. Sounds like fun. Might be worth a separate thread on the GT3 forum.

DTR.

Jack

DTR: I agree that developing small cracks over time is to be expected, but 6mm cracks after only 800 track miles does seem excessive to me -- I assumed the cause was heat buildup. I could have been misinformed by my Porsche tech, but I've been told that when the "tiny" cracks exceed 7mm and/or are connecting the cross drilled holes, Porsche recommends rotor replacement. Your thoughts/comments are always appreciated.

Dirt Track Racer

Okay Jack. But as I said above, the original post that started all this guessing states that:

Until the PCA DE Instructor shows me pictures that the cracks are connecting the holes or are any larger than the normal cross drilled cracks, I am not going to worry about the brakes on the GT3.

And I thought I already addressed your heat concerns by reminding you that the following day was expected to be 35 degrees. I don't live at VIR, but I live on the east coast and know that this time of year temperature swings of 50 degrees from day to day are rare.

DTR