My wife and I have been through on Going to the Sun roa 2-3 times on motorcycles.  Once was the weekend of the National Parks service 100th anniversary and entrance was free----that was a bad time!  Very crowded.  The last couple times, a few years ago, my wife was on her trike and I was on my Road Glide and we took turns.  I drove her trike the first time through and she road  passenger so she could look around without wrecking and then when we got to the west side, she drove the trike back east and I rode passenger so I could look around without wrecking! lol

    First time we went there, there was a thunderstorm and a land slide near Logan pass and the road was closed there--happened just as we got to the park.  Never opened back up while we were there so we went around the south side of the park and road back east from the west side to Logan Pass again.

   We went in late August, early September after all the schools were back in session so crowds weren't terrible.