Welcome to iRV2 . and the Newmar family.
Back in the day , Newmar used the Dutch Star name on both gas and diesel pusher coaches , so mentioning your chassis manufacturer ; or setting up a signature line with the info; is important to get the correct info for your coach .
Tire sizing info SHOULD , be on the decal with GVWR info in the area of the drivers seat ; ( mine is floor level on the wall left of the seat , by the seat belt retractor) if that decal has been removed , then finding the info from a member with the same coach on the same chassis will help get the factory tire size.