+3 wheels

[wantboost]

About how off would my speedo be with 18 '' wheels on a car that had 15'' from the factory. Is there any to compensate for this on a 240?

[g-ridda]

its not all about wheel size wut was your tire size when u had 15s and wut is your tires size on the 18s

[babowc]

^ right on the dot.
take your wheel size + factory sidewall x2
and make it = to 18" wheels + whatever aspect ratio.

[Cliff]

easy way is just get you stock size tire and your new tire size and go to like the bfg website and look up the passenger car tire specs and it will tell you a pretty close # but either way it will not affect you more than a mph or 2...i upsized my tires by 4" from stock and it only changed it about 5 mph

[aaronfelipe]

Here you go bud,
Tire size calculator.
Aaron

[wantboost]

thank you all.

[Doppelgänger]

here, plug your stock size in and you new 18" tire size to see how much of a difference it will be

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

[Allstar3.8T]

My buddys civic is a +6", all you do is check the rotational diam. and total height of OEM tire new, and what you want. Stay w/ in .25" on total height and you will see no drastic changes if weight is similar.

[aaronfelipe]

thank you all.

We love you too,

[wantboost]

....... lol