RCW 46.44.041
Maximum gross weights—Wheelbase and axle factors.
No vehicle or combination of vehicles shall operate upon the public highways of this state with a gross load on any single axle in excess of twenty thousand pounds, or upon any group of axles in excess of that set forth in the following table, except that two consecutive sets of tandem axles may carry a gross load of thirty-four thousand pounds each, if the overall distance between the first and last axles of such consecutive sets of tandem axles is thirty-six feet or more.
Just for a point, WA State is pretty clear here. The tires are what matters to them LEGALLY.
