Reminisce

Hey guys,

I know this was posted before but i cant find a thread with the info I need. I have the stock premium GT 18" wheels on my 12 GT, and its time to buy new tires. I'd like to start tracking my car later this fall and looking to get just a little more meat out back. The stock tires are 235/50/18 and i was wondering if there is a 255 I can get on there comfortably? If so what sidewall size, and is this a good idea?
Thanks folks.

Old Mustang Guy

255x45x18 is great on the stock wheel. That's what I have.

Dave07997S

If the OEM wheel width is just 8" you don't want to go above a 235 width tire. Can you fit a wider 255 tire on the wheel, yes, but it won't be optimal. Especially if you want to start tracking the car. The sidewall on a 255 width tire won't be properly supported with just a 8" wide rim. The V6 PP Mustang runs a 19X8.5 to run a 255 width tire (which is the minimum width for a 255 tire). If you want to track the car get ahold of a set of 19x9" brembo package wheels and you can run a 255 width tire properly.

Another suggestion, get the rear wheels widened to a 9" width. Several reputable companies do this.

Dave

Old Mustang Guy

My handling improved with 255's on the stock wheel. I would hazard to guess that you would be quicker on a track with 18's due to less unstrung weight and less rolling resistance. You could always go with an 18x9 wheel if you feel the need.

Old Mustang Guy

Excuse me, unsprung weight.

bob

Dave has a point, installing a tire that doesn't meet the minimum rim width requirements can really effect its performance.

Besides not being recommended, the tire has a less than optimal footprint and as Dave mentioned the lateral stiffness of the tire is marginalized

A good example of this would be to take a phone book stand it straight up and press down on the book, with no deformation its plenty stiff, bend the book in the middle and press down on it and all that lateral strength is gone. Same thing happens to a tire and it affects cornering and steering response.

The less than optimal footprint pulls in the sidewall causing them to bulge, bending the edges of the tread area up. This reduces the contact patch and in turn places more stress toward the middle of the tire which can effect wear and wet weather performance.

Broadly speaking, run the minimum suggested width to increase comfort and run the maximum suggested width to increase performance or any range in between to blend these attributes.

Avoid running to narrow or to wide rims. At best this can cause irregular wear or handling, at worse it can contribute to tire failure which can lead to all sorts of nastiness.

Poco

Check BFG tire website, they list section width,overall diameters of tires and rim widths showing just exactly how wide a tire you can fit on that particular rim without compromising any safety issues. Its a great reference point.

Stevedotmil

TireRack also does this except with all the tires on the site.