Will this fit?

[WhiplashGo]

Have 235/50/18 Pirelli tires on stock rims. Want to swap tires using same rims to Bridgestone Potenza RE-71R 245/45/18. Will these fit? 27.3" Pirelli, 26.7" RE-71R diameter. Width is 9.3" Pirelli, 9.6" RE-71R width. Tirerack says not any size RE-71R will fit 15' Mustang GT (Base GT) 18" rim. Is width the issue? Also, RE-71R 225/50/18 = 26.9" diameter, 8.9" wide shouldn't this fit as well.

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[sigintel]

Excellent question!
RE-71R is a handling oriented tire so I assume you dont want to have sloppy transition response: turn in, slalom, catching near spins after trail braking into a clover leaf too hot... Lol.

Jamming the widest tread on that will "fit" is more for looks if it causes the tread to roll towards the sidewall. Some moderate oversize is done by those looking to sacrific lateral handling for better stop light traction from a dig. You can run lower pressure and elongate contact patch for straightline grip.

Stay with in the mfg rim width spec so the tire can perform as designed.
Then try and stay within 0.5" overal diameter.
Sanity check load rating versus stock tires.
Double check speed rating.

245/45R18 was likely intended by Bridgestone to compete as an aftermarket Mustang base GT fitment:
8" rim width
26.7"OD is close to 27.2"
Load rating 97? = 730?kg = 1609lbs?
Speed rating W = 168mph

Yup, They built that tire just for you.

You could go 40 sidewall; however, you sacrifice street impact survivability, lower your gearing, harsher ride, and lower lateral grip on rough streets and cloverleafs with expansion joints etc. or anywhere compliance in the contact patch gives you advantage.

 

[jbailer]

You'll be fine, it is just slightly wider and a little shorter so your speedometer be off by just over 1 mph at 60 mph.

 

[Need4SpeedMotors]

Your good no issues with that tire size.

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