what would be the best performing tire size for the S4 GXL wheels(15x6). should I just stick with the stock 205/60, or wider, or skinnier(sp?) since the wheels are only 6" wide? after reading a post a few days ago, it made me think that a 195/60 tire might work better on a 6" wheel, and previously, I was going to try and stick the widest tire possible on these wheels. what should I get for the best performance?

BTW, I don't want to mess up my speedo too much.
thanks

 

I don't really have any suggestions as this is something I am researching now as well. However, here's a link to a tool that will give you an idea of how bad/close the tire size may hose up your speedo:

http://www.miata.net/garage/tirecalc.html

 

Stick with the 205/60 on the stock 15x6 rim.

Despite what many have posted, a 205/ 50, 55, or 60-15, is designed for 5.5 inch wide rim to a 7.0 inch rim. While a 6.5 inch rim would be ideal, the 6 inch rim is well within all tire manufactures size. To top that off, Mazda would have not made almost 100,000 FCs with 205/60-15 if they didn't think that was the best combination at the time for that car.

And frankly I am of the old school thought of get the most rubber that realistically will fit on the rim, for the best traction. Sidewalls on modern tires easily control the flex of slightly oversized or slightly undersized wheels. The exception to that statement would be using drag tires or other semi-pro and pro race applications.