I need a little input before I order the wheels that I want online. I have the stock wheels still on my 2014 GT base. I believe they are sized at 18x8. Will my stock tires fit on wheels that are 18x9 or will I need new tires for this wheel size. Thank you!

I believe the stock tires are 235/50/r18

 

In this case, the stock tire is 235mm, which is 9.25(ish) inches wide on the tread. The sidewall pooches out a little, but not much, and it's about 1.25 overall wider than the rim. You'd divide that in half, which is .625inch. Considering the pooch of the sidewall, the tire's widest part is about .75 inch on either side of the actual rim width.

So if you then put a 9" wide rim on the car, and used those tires, what would happen is that the sidewall will be more 'straight' up and down. It would almost be in line (guesstimate) and would be perfectly fine. However it may look a little... odd.

Consider this picture (linked because huge.) 2010 GT500 Convertible.

Look at the front wheel, then the back. The back can be considered 'what you have now.' The front would be 'what you'd wind up with'. The reason is that the stock GT500 wheels, at 18 x 9.5", carry 255/45-18s up front, and 285/40-18s in the back, so it's a good representation of the two looks you'll wind up with.

If you're cool with the front wheel's look all 'round, but with a taller sidewall, then you'll be just fine. Looks wise anyway. It may or may not induce a difference in turning, traction, etc. Won't really know until you try it though, but I expect it'd be fine overall.

Hope that helps!

 

Pirelli says 6.5-8.5 for that size which basically means they might have a little problem getting them to air up but after that you should be fine.

 

The answer is yes unless you like to live dangerously. Always stay within the manufacturer recommendation for the only four things keeping you from crashing.

 

Although my response really relates the 'wheel rash' thread elsewhere, it also seems appropos here.

I'm still running the stock Pirelli's. My '14 GT came with the 19 X 8.5 factory upgrade 5 spoke painted wheels but I replaced them with a slightly wider Boss 302S 19 X 9".

The upside was that the deeper offset and width helped fill up the wheel wells without need for spacers. The downside was that just a 1/2" difference in width caused the condition similar to what you illustrated with the Shelby front tires. As a result the wheel lip is flush with the sidewall, and damage has occured to the wheels from just the slightest brushes with curbs. It's far easier to remove scuffs on the tire sidewall than it is to repair gouges on the wheel.

A wider tire would have prevented this.

 

After reading the responses I have decided I will hold off on purchasing new wheels for now until I need new tires as well. No sense in buying new tires until I need them in my opinion. That's probably the best way to do it. Thanks for all the intelligent input, it really helped me make my decision.