There is some info for you in this tech tip http://www.stovebolt.com/techtips/wheels/

In the Accuride wheel catalog you'll find some great charts on wheel and tire interchange from tube to tubeless as well as minimum dual spacing for different tire sizes. Also what size spacer rings are needed. And even what rim widths are recommended and acceptable for different tires.
http://www.accuridewheels.com/completeversion.pdf

Doesn't concern your project, but while 20" and 22" cast spoke hubs are the most common size there are smaller ones used on trailers and old pickup trucks (Diamond T and Mack for two examples). There may even be larger ones out there on equipment and really big trucks?
Edit Yep, saw some 25" Dayton's on a Pacific heavy haul truck moving a 120 ton transformer near me yesterday: here are pictures http://rides.webshots.com/album/575013958ljWmXE

Grigg

Last edited by Grigg; 10/09/2009 1:19 PM.
•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-