Col de la Chenau

Overview

The Col de la Chenau is a hors catégorie (HC) climb, the hardest classification a road ascent can carry, and its numbers explain why. Over 26.5 km it lifts you from a start elevation of 388 m to a summit of 2102 m, a net elevation gain of 1714 m. The average gradient reads a deceptively civilised 6.47%, but the total ascent of 1887 m — well above the net gain — tells you the road is not a single clean ramp. It rolls, dips, and rears back up, and buried within it is a max gradient of 39.34% that will stop all but the strongest riders in their tracks. This is a full mountain effort: more than an hour and a half of climbing for most, an exercise in patience as much as power.

How the Gradient Unfolds

The gap between the 6.47% average and the 1887 m total ascent is the story here. If the road climbed at a constant grade, total ascent and net gain (1714 m) would be nearly identical; instead there is 173 m of extra vertical baked in, meaning the profile gives back terrain and forces you to reclaim it. Expect the honest average to be split between long sustained stretches and short, brutal spikes. The 39.34% max is an outlier — a ramp so steep it barely qualifies as rideable — but it warns you that this climb hides teeth. Treat the average as a floor, not a promise. On a 26.5 km ascent gaining 1714 m, even a "moderate" kilometre can sit well into double-digit percentages.

Pacing Notes

On a climb this long, pacing is everything. Ride the first two-thirds conservatively — the summit at 2102 m is a long way off, and blowing up on a 26.5 km HC climb means a very slow, very lonely finish. A steady effort anchored to your FTP is the right frame: aim to hold a sustainable percentage of it and resist chasing the steep ramps, where surging costs far more energy than it saves. If you do not know your threshold, run the numbers through the FTP estimator before you commit to a target. The 39.34% pitch is not a pacing zone — it is a survival zone. Shift down early, keep the cadence turning, and get over it without redlining.

Gearing

Come prepared to spin. For a 1714 m gain averaging 6.47% with pitches into the high double digits, a compact chainring paired with a wide-range cassette is the sane choice. A 34×32 is a reasonable minimum for strong climbers, but on the steepest ramps most riders will be grateful for a 34×34 — the extra sprocket buys precious cadence when the road tilts toward that 39.34% wall. If your bike accepts an even larger cassette, take it. Over 26.5 km there is no prize for grinding a gear too big; protect your legs early and you will still be pedalling at the top.

Summary

The Col de la Chenau is a genuine hors catégorie test: long, uneven, and punctuated by a gradient spike few climbs can match. Pace it patiently, gear it generously, and respect the distance from 388 m to 2102 m.

Length: 26.5 km
Average gradient: 6.47%
Max gradient: 39.34%
Start: 388 m
Summit: 2102 m
Net gain: 1714 m
Total ascent: 1887 m
Category: HC