Firestone

 

I forget the exact spec, but the ideal rake for these cars is something like 25-30mm difference with the rear being higher than the front obviously (confirm those numbers).. If you have the clearance, I would lower the front to get the rake in the right ballpark before raising the rear, but if you are clearance limited then adjust however you can to make it work.

 

25-30mm on a street car is not a good idea for many reasons!

996 full race/cup cars run around 21-25mm. Stock rake is around 5mm. I run 12-13mm on my stock bodied 996 NA race car and it is rock solid at up to 145mph, even when I get passed at that speed!

 

You're right, 20-25mm is the number I was looking for. That's why I said to search before someone tries setting up like that So many measurements and numbers run together when going from memory.

 

I just wanted to follow up on my experience below as I had the exact same problem as the OP.




I will tell you I had this feeling at 115+ MPH even after brand new OEM 19" 997 Turbo Wheels and brand new Bridgestone Potenzas installed.

I finally had a four wheel alignment done and all is perfect now.

The guy that did my alignment at NTB that had 20+ years of service experience said it was one of the worst he has seen in some time. It took him every bit of an hour, double checking everything and now it drives perfect. Best $89.99 I have spent in years....