i ordered 225/50/18 on an 18x7.5 +40 offset wheel.

im lowered on s-techs (1.4 all around)

should i have a smaller sidewall? what would you recommend?

Smaller sidewall for sure! 225/50 would be way to big even on a 17 inch rim, on a 18 that is huge. use this and see http://www.miata.net/garage/tirecalc.html

and your miles on the ODO will go up alot more becuase when your going 55 mph your speedo will read 60

225/40/18 would be a better match, closer to stock.

[/QUOTE]225/40/18 would be a better match, closer to stock.[/QUOTE]

Yea that^

For race or everyday use?

sorry buddy, you need to try again. Those tires will be very large.

EDIT: quick explanation: see my official wheel and tire sizing guide for a quick explanation of that middle number in the tire size. It's not a straight up measurement of sidewall height.

yea well i didnt order them directly. i work at a detail shop, and my boss ordered them. we called back and told them to switch it to 40 and they did. squared away.