Colle Arpeyssaou

Overview

Colle Arpeyssaou is a genuine hors catégorie (HC) test, the kind of climb that rewrites your idea of what a long day in the mountains feels like. Over 21.8 km it drags you from a valley floor at 588 m all the way to a summit at 2347 m, a net elevation gain of 1759 m. The average gradient sits at a punishing 8.08%, and unlike gentler HC climbs that hide their difficulty behind flat spells, this one keeps the pressure on almost from the first pedal stroke to the last.

That average is the number to respect. Sustaining 8.08% for over 21 kilometres is not a matter of one hard section you can survive and recover from — it is a full hour or more of climbing where the road simply refuses to relent.

How the Gradient Unfolds

With 1759 m of net gain spread across 21.8 km and a total ascent of 1746 m, the climb is remarkably consistent rather than spiky. There is no long false flat to reset your legs on, and the small gap between net gain and total ascent tells you there is virtually no descending along the way — everything you climb, you keep.

Think of it as three near-equal thirds, each roughly 7 km long, each holding close to the 8.08% average. The first third establishes your rhythm from 588 m. The middle stretches deep into the climb as the altitude begins to bite. The final third pushes toward the 2347 m summit, where thinning air makes the same gradient feel meaningfully harder than the numbers alone suggest.

Pacing Notes

On a climb this long and this steep, discipline beats bravado. Your FTP is the anchor for the whole effort: aim to settle just below it and hold there, because going into the red early on an 8.08% wall that lasts 21.8 km is a mistake you cannot claw back.

If you are not sure what your threshold power is, run the numbers through the FTP estimator before you commit to a target. A rider pacing at a sustainable percentage of threshold will reach 2347 m far fresher than one who chases the early ramps. Budget for the top third being the hardest — thinning air at altitude quietly steals watts, so hold a little in reserve for the drag to the summit.

Gearing

This is not a climb to be over-geared on. With 8.08% sustained for the better part of 21.8 km, you want spin, not grind. A compact 34-tooth inner chainring is the sensible starting point, paired with a wide-range cassette.

A 34×32 will get most fit riders up it, but on the steeper pitches late in the climb, when your legs are already 1759 m of gain into the day, you will be grateful for more. If your derailleur allows it, a 34×34 gives you that extra cushion to keep the cadence turning without blowing your pacing. Err toward the easier ratio — you can always leave a gear unused.

Summary

Colle Arpeyssaou is an HC climb that earns its rating honestly: long, steep, and unrelenting from 588 m to 2347 m. Pace to your threshold, gear low, and respect the altitude, and its 1759 m of vertical becomes one of the most satisfying summits you can reach.

Length: 21.8 km
Average gradient: 8.08%
Max gradient: n/a
Start: 588 m
Summit: 2347 m
Net gain: 1759 m
Total ascent: 1746 m
Category: HC