you may be spot on with your comment about the availability of the 245s over the 255s. i'm hoping to decrease understeer, so i'm gonna run the 255s when my wheels get here.

 

Me too. My tires probably will give me another 2000 miles at most, then I'm going to a 255 in the front. Even though the choices are slim in that size, there are still quite a few great tire options:
S-03
BFG KD
BFG KDW
etc...

 

I'm hoping to get a 2005 Track in a couple of months. One of the first things I want to do is swap out the rubber; I'm thinking about the S0-3's.

As we all know, the Track rims are 18x8" front and 18x8.5" rear.

Using DTD's caculator, I receieved the following:

Front

225/45/18 --> 245/40/18

Totals are in inches Tire 1 Tire 2 Difference
Sidewall Height: 3.99 3.86 .-13
Section Width: 8.86 9.65 .79
Overall Diameter: 25.97 25.72 -.25
Circumference: 81.59 80.79 -.80
Revs per mile: 800.92 808.71 7.79

Speedo reads: 65 Actual Speed: 64.37 (-.63 mph)


Rear

245/45/18 --> 275/40/18

Totals are in inches Tire 1 Tire 2 Difference
Sidewall Height: 4.34 4.33 .-01
Section Width: 9.65 10.83 1.18
Overall Diameter: 26.68 26.66 -.02
Circumference: 83.82 83.76 -.06
Revs per mile: 779.61 780.20 .59

Speedo reads: 65 Actual Speed: 64.95 (-.05 mph)

These seem to be the best matches when upgrading. According to Tire Rack's specs, the 245/40 will fit on an 8" wide rim but the 275/40 is designed for 9"-11". Is that running the rear too thin?

 

your rears will look like donuts. ask dealer if you can trade your stock wheels for some wider nismos. also, read everything you can on this site about wheel and tire sizes.