I have one and it fits pretty snug around the stock tire. The molded section is the width of the tire and attached to that is a strechable canvas/nylon section which you have to pull over the tire and it ends up behind the circumference of the tire which is what holds it in place. A taller tire prob wouldn't fit (unless you ordered the 17" one for a 16" oversize tire. -maybe)
A wider tire may fit because the stretchy part would take up some of the extra width. You'd just have less to tuck behind the tire. It's a pretty snug fit and requires some tugging even with the stock tire. Does that make any sense?
