Gregg,

If you would like to go with 325, somehow confirm that it won't damage the differential (there was a thread somewhere, maybe 6speedonline?). There is a tire calculator somewhere that I can't find now either, so following is 100% guess work on my part, as I don't know much about tires, or differential, and it's been a while since elementary math (someone corrects me if I am totally off the path).

Stock rear 305 30 19: Height of tire therefore 305mm x .3 = 91.5mm

Your planned rear tire 315 25 19: Height of tire 315 x 25 = 78.75mm

The stock tire is therefore about 13mm (.5 inch) bigger in radius. IOW your planned 325 replacement tire is SMALLER in diameter by 1 inch, and smaller in circumference by 3.1416 ( someone checks my math please) inches or so.

I vaguely recall from that old thread that the ratio of rear to front tire circumference has to remain around a certain range, or the differential will be damaged, and vaguely recall (not sure at all) that the poster was doing something similar to what you are doing.
Whether this 3 inch difference causes the ratio to exceed that range? I don't know.

Quote:
STRADALE said:

This is what I'm considering:

Michelin PS2's.
235/35/19 tires
315/25/19 tires

That way I don't have to make the tire swap from the stock wheels to the new wheels but the sensors are $98 each.