Hi,
I think I rode there at the very beginning of July and it was after awhile since the lolo pass was opened, so there was no snow on the road, except on the cliffs and mountain slopes. It was doable, weather wise, but there were lots of traffic. Since lolo pass is closed to cyclists from 11am to 5pm, I started rolling at 6am and by the time it was nine, I was near two thirds of the distance, and riding with heavy traffic. I was pretty annoyed with them not because any of them actually pushed me to the edge, but because it was just mentally exhausting to constantly have traffics behind you, trying to pass you, and at couple points, I literally felt that the air pollution was so bad, I could smell the busy city street, which was a bizarre..
And then when I got to the top, I met 7 other cyclists and one of them told me, if you climb the going to the sun road right after the lolo pass was opened, there's absolutely no traffic and it's just magnificent, minus it would be pretty cold when going down hill. Since I gave the ride only 5 out of the 10 experience, due to the bizarre traffics, it sounded pretty awesome, not having traffics at all. Really, the scenery is amazing(that I give 9 out of 10 stars), you might wanna consider doing it around that time. Call the Glacier National park visitor center and find out when the Lolo pass is opened to cyclists but not to auto traffics. Think it was due to snow residue on the road, which cyclists can go through with caution, but cars can't.
Again, think through it, cars are real pain in the butt when you trying to go uphill and you can't speed up, and they constantly push you to the side. Although most of the road have enough room for them to pass by you, there are some sections where you are at the spot where 15 cars are waiting for you behind you and all of them just having fun going up the hill without moving one finger is just annoying scene to look at.
My experience is negative because of cars, but hope yours isn't. Hope this helped.
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