is 225 the only width tire that will fit the stock 16x8 wheel?

 

No, you can also run 245/45 16 tires.

 

what about smaller sizes?

 

The narrowest tire u can put on an 8" wide wheel is 205, but a 215/50 or 55 would probably be best.

 

Why the hell would you want to go narrower?
Please don't reply for cost reasons.......

Putting aside other reasons, I think a narrower tire would look horrendous as the 225 sidewall is already pretty much vertical.