Would anyone know the max tire size for this wheel? 18" AMG factory wheels. I think the current tire size is 255/35/18. I want to get some more cushion from the tires. Would a 255/40/18 fit? or 255/45/18 ? thanks for anyone who knows!

 

Check this:

For the front:
6.5� to 7.5� wide wheel: 205 tires: +43 offset minimum
7.0� to 8.0� wide wheel: 215 tires: +48 offset minimum
7.0� to 8.0� wide wheel: 225 tires: +53 offset minimum
7.5� to 8.5� wide wheel: 235 tires: +58 offset minimum
7.5� to 8.5� wide wheel: 245 tires: +63 offset minimum

For the rear:
7.5� to 8.5� wide wheel: 235 tires: +40 offset minimum
7.5� to 9.0� wide wheel: 245 tires: +45 offset minimum
8.0� to 9.5� wide wheel: 255 tires: +50 offset minimum
8.5� to 9.5� wide wheel: 265 tires: +55 offset minimum
9.0� to 10.0� wide wheel: 275 tires: +60 offset minimum
9.0� to 10.0� wide wheel: 285 tires: +65 offset minimum

Good Luck! post pics of your car here.

 

anyway, you can calculate by yourself. http://www.miata.net/garage/tirecalc.html