From memory this is what I recall and I feel confident enough to suggest it.
5.5" = 7:00 tire
6.0" = 7.50
6.5" = 8:25
7.0" = 9:00
7.5" = 10:00
You can confirm this at any of the major repop tire companies websites.
That info until a couple weeks ago was in the Accuride wheel catalog... then they updated the catalog
http://www.accuridewheels.com/pdf/ProductsWheelsCatalogComplete.pdfNow on page 47 it only shows rim width allowed for tire size for tubeless wheels not the old 20". Note that there is a preferred rim width and an alternate or two.
The allowed rim width for tire size comes from The Tire and Rim Association, Inc. published in "The Year Book" and it only cost $99....
http://www.us-tra.org/publications.html...There is a web site that has which rims are the widow makers and which are safe enough to deal with.
Here it is
http://www.stovebolt.com/techtips/wheels/" 5.5" wide, 9 x 22.5 fit nicely."
I'm certain if you check with the Tire & Rim Association that will not be recommended.
I believe Ed's wheels are actually 5.25" wide between the lips, they're the very same wheels I'm running on my truck, and I also have 9R22.5 tires on them.
A 9R22.5 tire is supposed to be on a 6", 6.75" or 7.5" rim, not a 5.25".
Here are a few shots of them on a 5.25" rim.
http://rides.webshots.com/photo/2317319550080251109EeoORchttp://rides.webshots.com/photo/2493413700080251109bWLBHLI mounted them myself with absolutely no trouble, they slipped on as easy as could be. Looks like they have sufficient clearance between the duals and I expect loaded they will still.
Again, I know it's not recommended but it can work and 9R22.5 is the smallest 22.5" tire available these days.
Grigg