I don't think you can run a tridem in the states no matter the weight, NY and MI if you are properly licensed but I don't think the rest of the states recognize the spread.......I could be wrong but........
Michigan cuts your drives back to 32,000 when your trailer axles exceed 34,000. Remember a tridem in Michigan is only good for 39,000 (13,000 per axle) If you have a 60" spacing MOST US jurisdictions will give you 40,000 or more.
I run tridems in the US all the time. There are a lot of the states if you are licensed for the weight you can run 90,000 LBS gross with a tridem. If you are hauling a single pc load you can permit a tridem to 60,000 LBS and some states will even let you permit it to 70,000 LBS. I license to the max in most states and some of them I am licensed to 200,000 LBS gross weight.
Yes you can, some states recognize extra weight as well. Even in most of the other states you can run 48' tridems but have to abide by gross weights and also by axle pairings. Michigan and California are two that come to mind re 53' where you may have an issue...I've been out of this for a bit...anybody add to this?
Michigan had an issue with 53' tridems years ago but they resolved that. The only thing that I can think of as far as California would be with their 40' 6" kingpin to centre of last axle requirement it would make a terribly short inner bridge measurement.