I've been looking at U.S. car hauler low-deck flatbeds, so just FYI.
Max legal width is 102", many stay within 101.5"
Within the (usually removable) fenders, the bed width is usually at least 81"
Some manage to get to 83".
Which implies 9.5-10.5" width on each side, including the tire, fender width and airgap.