I just got a new set of 18x9.5 Chrome C5 wheels. I need to get tires. I was thinking of getting 245-40-18's in all four corners. This would retain the same tire diameter as my current 245-50-16's. Does anyone have opinions on the 245-40s? Is this enough meat for a good ride and for good performance? and should I go with a bigger tire in the back than in the front? I want to get BFGoodrich KD's. Any opinions on these type of tries?

 

with 9.5" rims you shouldnt run anything smaller than 275s unless you want the lip of the rim to hang out farther than the tire, which i think looks terrible. If i was running those size rims i would go 275 or 285/35/18

 

But if i put 275-35s on those rims will the tires be too wide in the front? Will the front tires rub onsharp turns or would I be ok? I do not want to do any fender mods if at all possible.

 

there are alot of people running 275/40/17s on 17x9.5 inch rims up front without problems. Id rather have alittle bit of rubbing than a tire that way too small for the rim

 

depends on what size adapter you choose to run but you should be running 275's.

use this...

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

245's on a 9.5

 

Well my adapters are 2 in. in the front and 1.5 in. in the rear. So 275-35s are the way to go? and In all four corners?

 

well what is the offset of the wheels then?

 

I don't know what the offset is. They are new C5 wheels from f-body motorsports.

 

well i suggest you find out before you put adapters on them.