the stock rims for my '97 A4 quattro were 16", and the stock tires were 205/55-16 are there any drawbacks to putting stock '02 A4 rims (15") with 205/65-15? or '06 A3(15") 205/65HR15? are there any adverse affects to worry about w the difference between the 55-15 to 65-16, or am i just being paranoid?

 

Go HERE: http://www.miata.net/garage/tirecalcold.html

You should be able to figure out what variations you can go with, size-wize... You want to stay as close as possible to the stock rolling (outside) diameter. As long as you keep it within 10-20mm of teh width, too, you should have no fitment issues. Best would be for you to talk to the guys down at your local tire store (asking a few key questions should allow you to determine if they know what they're talking about, or not. I like to open the ball with something easy for them to choke on, like: "Do you have "Z"-rated tires for my car?" Any answer OTHER than "Yes," or, "What size will you need" is cause for me to IMMEDIATLY walk awaay). after that quick verifyer you can start asking questions relevant to your needs.