I may have an opportunity to get a really decent price on the 2010 GT500 Convertible wheels (M-1007DC1895) which are the 18 x 9.5 wheels.

And are sweet.

Now, this means that my current 17x8.5 wheels are going to go bye bye, as are their stock 235/55 17 tires.

I've tried to figure it out... really I have. I've gotten so much confusing info from it, well, I've decided to let you guys talk me outta the tree.

I have no less than 4 different 'valid' tires that can go on those 18x9.5 rims. They are:
255/45 18, Front original for 2010 GT500 Convertible(?)
285/40 18, Rear original same GT500(?)
255/45 18, 1 mentioned suggestion for 18x9.5 for 4 corner S197 fitting.
275/40 18, other mentioned suggestion for 4 corners, S197.

Remembering that stock 17s are 235/55/17, these are all within percentage points of keeping the MPH the same-ish.

So... if it's a great deal, I'm gonna go ahead and take the plunge on the rims. But the rubber is the problem...

I figure the 285s are out unless I want staggered, and I do not.

The 255s seem awfully not-wide for the 9.5" rims, being about 10" wide themselves at the mid sidewalls.

Therefore the 275 seems to be the 'right' tire? But seems as if it'll be more prone to rubbing, without some sort of modification to the steering stops or a spacer?

I thank you all very much indeed for helpin' me get unconfused. And so does Awesome, I think she's virtually chompin at the bit for noo shooz.

 

I'm running 255 on 9.5" rims on the front , and your right they're just about at the limit , but I've had no problems with them ...

 

I'm running 255/45/18 up front and 285/40/18 in the rear with 2009 GT500 rims and it looks great. Not really staggered but gives the S197 an awesome stance. Here's some pictures if it helps.

 

Good choice on the rims as they are crazy cheap! I even bought an extra pair for my drag radials.

I went with the staggered tire tire set-up... 285/40 rear, 255/45 front.

 

Staggered 255 - 285 here 2008 GT500 wheels (18 x 9.5).. no issues other then the GY F1's they come with are **** for grip.

 

I run 255's on my GT500 wheels (18x9.5) on all four corners with no problems. But when I need tires I'm going with 275's on all fours because they'd be a better fit on the 9.5" wheel.

 

Yea these Goodyear F1 don't grip for anything. Defiantly getting nittos when the time comes for new tires. Or maybe toyo proxi. Idk which ones are better

 

275/40R18's will be a tad onthe short side at around 26.7"

3/10ths of an inch might not sound like much, but on a stock height car it might be noticable.

Also check the load rating and make sure the tires can handle it (just match the load index which is part of the alpha numeric sequence indicating the speed rating as well), you may have to find an extra load tire in that size but that is not only good from a load index standpoint but if for some reason you decide to make a banzai run out in the middle of nowhere you can be confident that from a speed standpoint at least the tires wont do something unintended.

A word on using 255/45R18's though, since an 18 x 9.5" rim is the upper limit for a 255/45R18 it offer the most responsive tire since there will be the least amount of deflection in the tire.

A 275 and 285 series tire will start to approach the lower limit for these tire sizes and conversely offer less overall response but a more probably comfortable ride.

Lateral road holding may or may not be better in any case since rim width can effect this and is not nessecarily a pure function of tire size.

 

I appreciate it. Makes sense