Col d'Andrion

Overview

The Col d'Andrion earns its Hors Catégorie rating honestly. Over 12.5 km it averages 9.29% — a gradient that demands respect from the first pedal stroke — and somewhere on its flanks the road briefly rears to a recorded maximum of 55.66%. That figure is almost certainly a data artefact or a ramp-length outlier rather than a sustained wall, but it signals that isolated sections are steep enough to stop an under-geared rider cold. Total ascent logged is 1,698 m against a net elevation gain of 1,160 m, meaning the road undulates enough that you reclaim some lost height before the final push.

Gradient Profile

Starting at 527 m and finishing at a summit of 1,687 m, the climb covers 1,160 m of net vertical in 12.5 km. The arithmetic average of 9.29% means there is no easy lower slope to spin out your legs — the road is consistently hard throughout.

A few things to expect:

• No genuine flat section to recover. At 9.29% average across the full length, any section sitting below 6–7% is a relative gift, not a rest.
• Localised ramps. The gap between the 9.29% average and the recorded maximum gradient indicates the profile is not uniform. Expect periodic steeper pitches that will spike your power output well above your sustainable threshold.
• Cumulative fatigue. 12.5 km at this average gradient takes most trained cyclists well over an hour. Pace accordingly — blowing up at kilometre 8 leaves a very long, very painful walk to the top.

Pacing Strategy

The HC category and 9.29% average call for a conservative opening. If you have a power meter, target a percentage of your FTP you can sustain for the estimated duration of your ascent — use the FTP estimator if you need a current baseline before attempting this climb.

Key pacing principles for Col d'Andrion:

1. Start below threshold. The temptation on any long steep climb is to match the gradient with effort. Resist it for the first third.
2. Pre-empt the ramps. When a steeper pitch appears, shift down before your cadence drops rather than grinding through it. A short burst at high power is survivable; a sustained grind at near-zero cadence destroys the rest of your climb.
3. Manage the undulations. The difference between 1,698 m total ascent and 1,160 m net gain means there are descending or flat sections in the road. Use these to recover briefly rather than accelerating — saving legs for the upper kilometres is worth more than the seconds gained by pushing on a descent.

Gearing

Do not underestimate this climb on gearing. At 9.29% average with ramps considerably steeper, a compact chainset (50/34 or smaller) paired with at least an 32-tooth cassette is sensible. Riders on standard doubles should verify their lowest gear produces a comfortable cadence at or above 70 rpm on a sustained 10–12% pitch before committing to the ascent. Arriving at a steep ramp with nowhere left to shift is a fast route to a blown climb or a knee problem.

A 1× drivetrain with a wide-range cassette is increasingly popular on HC climbs of this character — the simplicity of shifting under load can outweigh the chainline compromise on a road this sustained.

Bottom Line

Col d'Andrion is a full-commitment HC ascent: 12.5 km, 9.29% average, 1,160 m of net gain from 527 m. There is no easy section to bank time or recover. Arrive with appropriate gearing, a realistic pacing plan anchored to your FTP, and the patience to ride the first half conservatively. The climb will punish anyone who treats the early kilometres as anything other than investment in the final ones.