I've seen wheel/tire vendors pairing 17x7 wheels with both 215/40/17 and 205/45/17 tires? which is correct? Thanks.

You'll probably find all the info you need on the Tread and Butter forum.
But to save you the trouble: 205/45-17.

You may find the info you're looking for in this thread:

http://www.scionlife.com/forums/viewtopic.php?t=31340

Both 205/45R17's and 215/40R17's will work equally well with out creating any problems!

Has anyone tried 225/45/17? There are alot of potholes in the Bay Area and trying to see if they would fit without lowering the Xb?

215/45R17s here with no problems. Speedo is exact too.

don't forget that rim width will have have an effect on the overall tire diameter. I have 215-40/17 on a 7.5 wide wheel. according to the police radar trailer that was on my street, the speedo was close enuff.

Rememeber, speedometers are only an approximation. Tire pressure and tread wear are also factors. The only true reading is by getting calibrated at a speedo shop.

IIRC, the speedo in my Crown Victoria was 2 mph faster than actual.

Wheel width, sizes, and offsets will all play a prat in the correct tire sizing on your car.

If you're gonna' run a 16x8" wheel, you'll want to stretcha little, and you'll be able to run a larger tire.

But for a 17x7 or something, 205's or 215's is plenty.

I ran a 17x10 (-20et-) on my Mk4 Jetta, with a 235/40-17.

The factory wheel sizes are 15x6.5 with a 35et and like a 195/65-15.

Just size it up, and be smart. You'll be just fine.