MarcD147

it was recently suggested to me that it is possible to use Cayenne rotors on a 996 cup. mostly to save money. I assume others have tried this so I am looking for feedback/guidance and some details

it wasn't clear to me what modification was required to do this
is this PCA GT3C legal?
how durable are they?
what is the expected cost benefit?

Viperbob1

There is a definite $$ incentive as you can get some ATE rotors with grooves for just over $100. Now the downside is they are heavier than the GT3 ones. They are durable and legal as they are single piece rotors. You are going to give up performance due to the weight. Most racers look to remove unsprung/rotational weight, not increase it

MarcD147

thanks Bob for the quick reply !!

fstockcarrera

They work great. You will need to drill the drive pin holes to fit the cup center lock pins.

Steve113

I have them they work great

Viperbob1

Yes on the rotor for the used on the Cups, the lugholes need to be increased 1mm. Not very much and easy to do with a handrill SLOWLY. Ideally you want a press and a way to make sure larger holes are perfectly centered.

bauerjab

What diameter drill bit do you need? Thx.

dwe8922

I run them and they last a long time. They're heavier.....

I started running the Deman rotors, which I understand are cayenne rotors. I cut off one of the mounting plates, and attach it to the ATE rotor with vise grips to give a guide for enlarging the holes. Then I drill it with a press. You also have to drill for the countersunk mounting screws if you want to use them.

Im curious to try the lighter Girodisc rotors though.....

James P

You will need a 16.5mm drill bit & best to use a drill press

Viperbob1

The lighter GIRO Disc does make a big difference in both acceleration and braking... GTC3 does not allow for 2 piece floating rotors, but you can simply use the small bolts and bolt the hats to the annulus.

bauerjab

Bob, Was wondering what you meant my "big difference." Steve K has track records at LRP and NJMP. Bob. S has run 156s at the Glen. Both say the Cayenne rotors are fine. Thanks in advance.

fstockcarrera

John the least of our worries are the front rotors weight. Academically Bob is correct but practically they are not holding you back at the Glen. Steve drives
at a level us mere mortals could only dream.

bauerjab

That is exactly my point. No dispute that less unsprung weight, less rotatational inertia, etc. would be better - at least theoretically. But, as a practical matter, what is the "big difference." I doubt there is any practical "big difference" for people not racing at the highest professional level. But maybe there is and I am willing to learn something. For me, the "big difference" would be "less brake...more gas..."