Reaching the summit via Le Bourg-d’Oisans (south) is known as one of the most beautiful climbs in the Alps
To start with the longest. You will reach the summit by starting from Le Bourg-d’Oisans (south). This side is known as one of the most beautiful climbs in the Alps, also this is the first climb of the legendary cycling event Marmotte Granfondo Alpes. Basically you climb most of Col du Glandon, as Col de la Croix de Fer is on the shoulder of this climb. You will climb all the way up to Le Chalet du Glandon before making a right to the Iron Cross. The full distance is 32km against an average of 4%. It goes up and down, the road winds through forest and open high meadows, the gradient changes from steep to relatively easy going in the space of a few kilometers.
When you start from La Chambre, you will ride the hardest. It includes the northern climb of Col du Glandon. You have a killer last two kilometers exceeding 10% with stretches of 12%. To reach the summit you need to battle against an average gradient of 7% for 22.7km.
The more steady climb can be accessed from Saint Jean de Maurienne. Especially the last 5 or 6 kilometers are stunning leading you to the summit via a hair-pinned road. In total you have to overcome a distance of 29.5km against an average of 5.5%.