O.K. I have wheels on my golf cart too, but not spinners. George has seen them, and wanted to steal them in Illinois, until he found out they were 10's. (I guess I'll have to post pics of that too!)
Anyway, the difference between 18's and 16's is night and day. I started in a outlaw group and all we ran was 18's. Made the switch to USLMRA rules and 16" tires. HOLD ON! Get a 16x7.5x8 on a 8"x8" wheel, that tire will be square. Not that round 18 on a stock wheel.
Been there done that! 18's Suck!
Paul