Fast240Z

I have P195/70R14 tires on my Z, so I'm assuming that means I have 14" rims. I was wondering how much wider I could go on my tires with my 14" rims I have now.

BoulderZ

I've seen a variety of specs/rules of thumb posted on that. The most common one I see is the "Not more than a half inch wider than the width of your wheel". Here's one site that says that and also has some great general wheel/tire sizement info (like calculating width by aspect ratio and other fun party games):
http://www.cloverleaf-auto.com/wheels_tires.htm
Dave

ezzzzzzz

Manufacturers typically state the a rim/wheel should not be less than 80% the width of the tire. When looking at tires the specifications will list minimum and maximum rim width for any given tire size.