Bolt Pattern, Tire Question

We've discussed this before. The bolt pattern is the same as the 99-04: 5 x 114mm (5-1/2")

The offset (back spacing) is higher than the old Mustangs. I is 45mm on the GT - 39mm on the V6.

Mustang GT tires P235/55WR17

P = Passenger car tire

235 on the tire designation is the tread width in mm.

55 is the aspect ratio. It means that the sidewall height is 55% of the tread width (129 mm in this example)

W = Speed rating of the tire

R = Radial

17 is obviously the wheel diameter in inches.

Don't ask me to explain why wheels are still in inches and tires are in mm.

I belive that the wheel width on the GT is 8".

If you change tires and wheels, usually you want to maintain the same tire outter diameter. So if you go to 18" wheels and tires you would want to go to a lower aspect ratio tire. For example the optional 18" tires for the '05 Mustang (if we ever see them) are P255/45ZR18 They have approximately the same diamteter as the 17" tires.

As far as wheel width goes, usually to take full advantage of wider tires, you will need a wider wheel. If you go to 235 to 255 tires you would want a wheel at least 1/2" wider but no wider than +1"

For more information go to an internet retailer like tirerack.com