Col de Sageroux

Overview

Col de Sageroux is not a climb you ease into — it is a sustained wall. Over 13.1 km it averages a savage 12.13%, and that number alone tells you almost everything: there is no flat, no recovery, no false valley to catch your breath. From a start elevation of 668 m, the road claws its way to a summit of 2254 m, a net gain of 1586 m packed into a distance most riders would consider a warm-up on gentler terrain. It earns its HC — hors catégorie — rating without argument. This is a climb measured not in kilometres but in survival.

How the Gradient Unfolds

A 12.13% average is punishing on its own, but averages hide the teeth. The max gradient here hits 33.18% — a ramp so steep that on many bikes it is barely rideable seated, and on some, barely rideable at all. Expect the gradient to swing hard around that mean: long double-digit stretches broken by pitches that spike toward the maximum. With a net gain of 1586 m and a total ascent of 1544 m, the road climbs relentlessly upward with almost no descending to inflate the distance — nearly every metre travelled is a metre gained. Plan your effort assuming the worst ramps arrive when your legs are already deep in the red.

Pacing Notes

On a climb this steep, pacing is less about holding a target speed and more about protecting your power ceiling. Ride the first kilometres well below your FTP — the 12.13% average will drag your effort upward on its own, and the pitches toward 33.18% will force short, unavoidable surges over threshold. If you spend those matches early, the upper slopes will end your day. If you do not know your threshold, run the numbers first with the FTP estimator so you can anchor your effort to real data rather than optimism. Break the 13.1 km into mental segments and treat each steep ramp as its own problem, settling back below threshold the moment the road eases.

Gearing

Gear for the maximum, not the average. On a 12.13% mean with spikes to 33.18%, most riders will want the largest cassette they can fit. A compact 34-tooth chainring paired with a 34×32 is the practical minimum here, and even that will have you grinding on the steepest pitches. If your derailleur and hanger allow it, go to a 34×34 for real headroom — the extra cog is the difference between spinning and stalling when the road tilts toward its worst. On a 1586 m ascent, a cadence you can actually sustain matters more than gear ratios that look fast on paper.

Summary

Col de Sageroux is a genuine HC test: short in distance, enormous in vertical, and unrelenting in gradient. Come with low gears, a conservative plan, and respect for what 12.13% over 13.1 km does to the legs.

Length: 13.1 km
Average gradient: 12.13%
Max gradient: 33.18%
Start: 668 m
Summit: 2254 m
Net gain: 1586 m
Total ascent: 1544 m
Category: HC