Because of heavy traffic and slim shoulders, bicycle travel along Going-to-the-Sun Road [1] is restricted during the busy summer months. From June 15 to Labor Day, bikes are prohibited on the road between Apgar [2] and Sprague Creek Campground, and between Logan Creek and Logan Pass [3], 11 a.m.–4 p.m.
Logan Creek, at the base of the Loop, is about 10 miles from Sprague Creek Campground and about six miles from Avalanche Campground. Between Apgar and Logan Creek the road stays in the McDonald Creek Valley, climbing some but not dramatically. Shortly after it crosses Logan Creek, the road really takes off uphill.
Expect the ride between Logan Creek and Logan Pass to take three hours, and expect to feel more exhilarated than exhausted upon reaching the summit.
Cyclists who’d rather not dodge the cars on Going-to-the-Sun Road can bike the paved trail between Apgar and the park entrance. Also starting in Apgar, Camas Creek Road heads up toward the North Fork area, and it is paved for the first 12 miles.
Links:
[1] http://www.moon.com/destinations/montana/glacier-national-park/lake-mcdonald-valley/sights/going-the-sun-road
[2] http://www.moon.com/destinations/montana/glacier-national-park/lake-mcdonald-valley/sights/apgar
[3] http://www.moon.com/destinations/montana/glacier-national-park/logan-pass-st-mary/sights/logan-pass