I use this thing
http://www.rimsntires.com/specs.jsp
your running 275/55/20s i guessed at 9 inch wheel-31.9 diameter with a 10.8 footprint
compaired to a 275/45/22 on a 9 inch wheel- 31.8 diameter with a 10.8 footprint. hope the link and info helps i use this all the time.