This is one of my favourite winter Alpine loops. I usually do it in the opposite (clockwise) direction (up the east side of Col des Glières – details and video here).
Both sides are beautiful, steep climbs with plenty of hairpins and great mountain views.
Both sides are paved, and in summer could be done by road bike – although the east side is very bumpy. But to join the two sides requires 2 kms across a gravel road (for this ride I took a groomed snow-shoe trail)
The ride was plenty cold – and I was without water as it fairly quickly froze. But I had plenty of spare layers and the sun was out so no worries.
The Bottom of the east side: