Here's a list of the overall diameters of the various sizes of tires used on the 850:

195/60/15 = 61.50cm

205/50/16 = 61.14cm

205/45/17 = 61.63cm

215/40/17 = 60.38cm

215/45/17 = 62.53cm

And here is a list of the approximate circumfrences of the tires, or the distance covered with one revolution:

195/60/15 = 386.4158964cm

205/50/16 = 384.1539497cm

205/45/17 = 387.2327105cm

215/40/17 = 379.9378728cm

215/45/17 = 392.8875773cm

From what I have gathered on this board, all of these tires fit regarding rubbing except for the 214/45/17. It seems one or two people get away with this tire, but in general, at full lock, it rubs.

As for differences in circumfrence, what is considered an acceptable difference? And compared to which circumfrence?

When you think about it, the stock non-turbo and GLT low pressure turbo, as well as recommended snow/winter tire sizes for the base, GLT, Turbo, T5-R and R, is 195/60/15. And the Turbo, as well as some T5-R's and R's came with 205/50/16. And lastly, the some T5-R's and R's came with 205/45/17.

If you compare the three, there is more than a 3cm discrepincy between the smallest and the largest.

So what circumfrence do I use as a reference point in determining acceptable difference in circumfrence? And once again, what is considered an acceptable difference?