ok im really not understanding this tire to rim thing.
i tried searching here but cant really find an answer to my question.

the tire that comes on it is 215/45/18
from what i read it 215mm wide, 45 still dont know, and 18 rim opening size

but now i read on another post in here that someone thinks the widest tire could be 245. but what would the middle number be?
i would assume it would be 245/ xx / 18.

but how would you know what tire would fit what rim or vs versa.
like this tire. goodyear eagle F1 for example.
off the goodyr site i got this
Tire Size -----225/50ZR18
Service Description --95Y
Sidewall ------VSB
Approved Rim Width ---6.0-8.0
Meas. Rim Width ---7.00
Section Width ---9.2
Outside Diameter --- 26.9
Tread Width ----7.8
Max Load ------1521 @ 44

so does that mean the 225 tire will fit all rim widths from 6-8"

but then there is 225/40ZR18
huh???
sorry for sounding like a nob but i am :D lol

The easiest way to understand without going in techicalities and tire terminology..

The first number is the width of the tire. 215 is most suited for 7" wheels like the stock gts wheels. Then as you move to a wider wheel, 7.5", 8", etc.. you would want to look for wider wheels 225, 235, etc..

The second number is the side of the tire. So the point where it contacts the edge of the wheel/rim to it's tread. The bigger the number, the bigger/higher/taller the side of the tire will look.

The Z is a speed rating, and in this case I believe it's a rating saying that the tire is safe up to 150mph or higher than 150mph. Or maybe it was 155, vice versa. I don't really remember, but you will see ratings like Z, V, H, etc..

http://www.discounttire.com/dtcs/infoHome.do

Everything you could possibly need to know about tires and wheels.

awsome guys thanks,

looks like the widest tire we can use on the gts if im reading it right on the info link is 225.

you can fit a 235 series tire, but will have the same contact patch as the 225 would.
In other words, it ill give you the LOOK of a wider tire, but the traction of the smaller size tire.