Would 265/35 tires be ok to put on 18 x 8.5 wheels? Any problem with the speedometer reading? Thanks

 

The tire size thing is pretty simple math...

Stock:

235/55-17, so 235mm wide / 25.4 mm/in * .55 aspect ratio * 2 + 17 rim = total tire height. = 27.55" tall

265/35-18, so 265mm wide / 25.4 mm/in * .55 aspect ratio * 2 + 18 rim = new total tire height = 25.57" tall

You could calculate the circumferense (2*pi*radius or pi*diamter), but that is linear, so you can just as easily calculte the speed difference with total tire heights:

(Old height - New height)/Old height = -0.06896 (-6.896%).

So, at an indicated 60mph, you would actually be going 55.86 mph. And the GT looks like it needs bigger tires, not smaller to look right...

 

Understood, thanks! I'll take 255/45-18

 

That's what I put on my GT. I think they look good. You can even have your friendly Ford tech recalibrate your computer to comp for the size like I did. I love freebies!