[wayner]

I run a 245/40/17 on the front. (275/40/17 rear)

In a 245. when I compared the 40 to a 45 the numbers looked like this:
40 front = 24.71
45 front = 25.68

If you step up to a 255 like NY65912 suggested, check the diameter, likely sticking close to 25"

I know many guys who run a 315 on the rear run a 255 up front.
Not all manufacturers have the same combinations either.


Nito NT01 comes in a 255/40ZR17 24.92"
Hoosier R6 only comes in a 45 but diameter is larger 255/45/17 26.20"


For reference, Nito lists these for their NT01 (the last number is the diameter)

255/40ZR17 24.92

235/40ZR17 24.40
245/45ZR17 25.55
255/40ZR17 24.92
275/40ZR17 25.55
P315/35ZR17 25.43