How would one calculate wheel sizes when switching to different configurations? For example, say stock is 225 50 16, and one wants to go to 205 for winter? Do you multiply the 225 by 50% to get the amount of side wall? Therefore, to go into 205 one would get 205 55 60? eg. 205x55% is 112.5mm.

Also, if going from 225 50 16 to 225 50 17 there would be an extra inch in diameter, therefore the speedo will be off.

I have 225 50 17 on my car (non-CLS) and want to get something better for winter. IF I stay the same size I know the tire will be expensive for one, and 225 is wide for winter. Going to 205 55 16 would be the best idea?

 

This should help. Check this post I started a while back. It has three or four tire size calculators on it.

http://www.acura-cl.com/forums/showt...threadid=37876