I have a year 2000 996 with 18 inch wheel. front is 7.5 inches wide and the rear are 10 inches wide. I'm not happy with how my car tail wags when manuvering at speeds above 60 to 70 mph....it's scary....I think wider wheels
and lower profile tires would make the car handle better and be less scary at speed....I do have the X74 suspension package and that is a terrific improvement.
Any reccommendation on wheel size and tire sizes? this is a street car only....Thanks

 

Tires are key to handling.Try a Michelin PS2.

 

What kind of tires are you running?

There should be nothing scary at 60-70mph that would need anything over stock.

I would suggest finding some stock rims and tires and see what you get. No sense in spending a bunch on new wheels when that is most likely not the problem.

 

You should check to see if your wheels are bent or damaged first.

 

Sounds like you are in need of a good alignment as well. The car is a little squirrely but not at those speeds. Check your alignment specs and make sure its good. Tires won't make your car feel squirrely like you are describing.