Col du Granon

Overview

The Col du Granon is short in distance and merciless in everything else. Across just 8 km the road climbs 1007 m of net elevation, from a 1391 m start to a 2398 m summit, at an average gradient of 12.58%. That average alone tells you almost everything you need to know: this is not a climb with a hard section buried inside an otherwise steady grind. It is hard from the base to the top, an HC ascent — hors catégorie, the toughest classification there is, above categories 1 through 4.

At 12.58% sustained over 8 km, the Granon sits among the steepest paved climbs a rider will ever attempt. The total ascent of 1173 m — slightly more than the net 1007 m — hints at the odd brief dip or flatter breath, but those moments are rare enough that you should not plan a recovery around them.

How the Gradient Unfolds

Think of the Granon as a near-continuous ramp rather than a climb with distinct phases. Starting at 1391 m and finishing at 2398 m, the road gains altitude at roughly the same punishing rate throughout. With an average of 12.58% and no meaningful respite, every kilometre demands the same effort as the last.

The gap between the 1173 m total ascent and the 1007 m net gain is small, which means very little of the climb gives elevation back. There is almost nowhere to freewheel and recover. What you climb, you keep. Treat the whole ascent as one long effort held just below your limit, because the mountain will not hand you a rest.

Pacing Notes

On a climb this steep and this even, pacing discipline is everything. The single biggest mistake is starting too hard on the lower ramps and paying for it long before 2398 m. Anchor your effort to your FTP and hold a wattage you know you can sustain for the full duration — on gradients near 12.58%, there is no coasting to bail you out of an overcooked start.

If you are not sure what power you can hold for a climb of this length, use the FTP estimator to set a realistic target before you arrive. Then ride to that number, not to the riders around you. On the Granon, a steady effort held honestly from 1391 m will beat a heroic surge every single time.

Gearing

Gear for survival, not for pride. A sustained 12.58% over 8 km punishes anyone who arrives undergeared, so bring the lowest ratios you can fit. A compact chainring paired with a wide cassette is the baseline: a 34×32 is the minimum I would consider, and even that will feel tall when the gradient bites.

For most riders, a 34×34 is the smarter choice, giving you a genuinely spinnable gear to protect your legs across the full 1007 m of climbing. If your bike and derailleur can accommodate something lower still, you will not regret it. Preserving cadence on a climb this steep is what keeps the whole 8 km survivable.

Summary

The Col du Granon is a pure test of climbing: 8 km, 12.58% average, 1007 m gained to a 2398 m summit. Gear low, pace to your FTP, and respect the mountain from the first metre.

Length: 8 km
Average gradient: 12.58%
Max gradient: n/a
Start: 1391 m
Summit: 2398 m
Net gain: 1007 m
Total ascent: 1173 m
Category: HC