shastsmae

i was thinking about getting aftermarket wheels. my concern was will the bigger size throw the speedo off or will the car be slower? im going from the stock 17's to just 18; i would really prefer to get wheels over just a new set of tires. but if upgrading the wheels will slow me down i prally wont getem.....lmk, thanks

seanmcd

If you go UP a size with your wheel, you simply adjust your tire size to match the original circumference. Is that how you spell circumference? Becuase I don't think I've had to spell that since middle school or something...

Look for a wheel/tire calculator or search for "plus one" and tires and you will find some info. Or search around here. Also study up on OFFSET. You don't want your wheels sticking out too far. To me, by far the worst look on any car.

GreenMonster

Yeah, the speedo will be incorrect if you use a tire that is a different size from the OEM...

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

RaviNJCLs

iTrader: (4)

It's not going to slow you down, although the wheels may be heavier than stock, but I really wouldn't be too concerned about it. I had 19's on my car for the summer and the tire size was 235/35/19 and it did not throw off my speedometer at all. I think if you go with 225/40/18 you should be OK.