The last time I was at Glacier NP, they were more than very strict about the 21’ length restriction with my 22’6” Class B motorhome. It was late September when most of the Park was already closed (no shuttle busses or Red Jammers), and the absolutely humorless ranger at the St. Mary's entrance station to Going to the Sun Road was extremely direct and pointed in telling me that I was limited to going no farther than the Rising Sun Boat Ramp. As I drove the 15 minutes there, I found an NPS police car driving right behind me; somehow I had the feeling the ranger at the entrance station sent this officer to make sure I didn’t drive my motorhome over Logan's Pass.
It was quite frustrating to me, especially since I know the NPS Sprinter shuttles the exact same size as mine go over Logan's Pass several times per day during the busy season. My guess is that they don’t want longer vehicles competing for the limited and shorter parking spaces along the roadway, and I guess they have to draw the line somewhere. However, I do resent the lack of seasonal discretion this ranger seemed to exercise.
Rock Doc
2014 Pleasureway Plateau TS in 2013 Sprinter 3500