Col de la Croix des Combes

Overview

Col de la Croix des Combes is a genuine hors catégorie ascent, and the raw shape of it explains why. Over 21.5 km the road climbs from 415 m at the base to 1906 m at the summit, a net gain of 1491 m. The average gradient reads 6.94%, but that single figure hides a lot: the total ascent of 1552 m is higher than the net gain, which tells you the climb is not perfectly smooth — there are dips and false flats that give back some altitude before demanding you earn it again. At HC, this is the hardest category on the road, and it deserves respect from the first pedal stroke.

How the Gradient Unfolds

The headline number to fear is the 29.07% max gradient. That is far beyond a sustainable effort for almost any rider, and it means somewhere on this mountain there is a wall you simply survive rather than ride cleanly. The gap between the 6.94% average and that spike is enormous, so expect the climb to swing between long steady stretches and short savage kicks. Because total ascent (1552 m) exceeds net gain (1491 m) by 61 m, you will lose a little height at points — welcome recovery, but also a reminder that every descent must be re-climbed. Over 21.5 km, that irregular rhythm is what makes pacing so difficult.

Pacing Notes

At 21.5 km, this is a climb measured in tens of minutes, not seconds, so pacing discipline matters more than raw power. Anchor your effort to your FTP and try to hold the steady 6.94% sections just under threshold, leaving headroom for the ramps toward that 29.07% max where your power will briefly spike whether you like it or not. If you do not know your threshold, run the numbers through the FTP estimator before you commit to a target. The riders who blow up here are the ones who treat the early kilometres like the average and ignore that 1491 m of climbing is still ahead. Start conservatively, and let the mountain come to you.

Gearing

Do not under-gear this one. With a 29.07% max gradient and 1491 m to grind out over 21.5 km, you want the lowest ratio you can realistically fit. A compact 34-tooth chainring paired with a wide cassette is the sensible baseline: a 34×32 will get most trained riders up the sustained 6.94% sections, but for the wall and for the back half when fatigue bites, a 34×34 gives you the extra margin to keep spinning rather than grinding to a stall. If your bike accepts it, err toward the easier gear — you will never regret having it on an HC climb of this length.

Summary

Col de la Croix des Combes is a long, uneven HC test: 21.5 km, a 6.94% average that masks a 29.07% max, and 1491 m of vertical from base to summit. Pace it off your threshold, gear low, and treat every false-flat recovery as borrowed time before the next ramp.

Length: 21.5 km
Average gradient: 6.94%
Max gradient: 29.07%
Start: 415 m
Summit: 1906 m
Net gain: 1491 m
Total ascent: 1552 m
Category: HC