Nope 40 series tires and wheels are 3.8" in diamiter...
40 series refers to the older tires and wheels that use the old style double bead. Where the 3.8 uses the Traxxas style or 1/8 buggy bead, that's the only difference. Traxxas/8th scale buggy bead is more simplified and easier to glue. The only 40 series (old bead style) stuff Pro-Line still has are the Tech 5 40 series wheels and Trenchers 40 series tires.
Trencher X 3.8's are substantially wider then Trencher 40 series...
Hope that makes sense OP lol.