Col d'Arriel

Overview

Col d'Arriel is a hors catégorie climb that earns its rating the honest way — through sheer length. At 31.2 km from base to summit, it is the kind of ascent you settle into rather than attack, a effort measured in tens of minutes rather than a handful. From a start elevation of 627 m the road threads upward to a summit of 2259 m, a net gain of 1632 m over the full distance. The average gradient reads a deceptively mild 5.22%, but that number hides the story: with a maximum pitch of 17.7%, the climb is anything but uniform. Anyone treating the average as a promise will be caught out by the ramps.

How the Gradient Unfolds

The 5.22% mean is best understood as a blend of easier valley kilometres and much steeper walls stacked on top of them. Total ascent registers at 1577 m against a net gain of 1632 m, and that small gap between the two tells you the profile is not perfectly monotonic — there are stretches that ease or nearly level before the road tilts up again, meaning the true climbing sections must be steeper than the overall average to reach 2259 m. Expect long ramping middle grades punctuated by the 17.7% maximum, most likely on the shorter, sharper pitches. Treat the climb as a series of stepped efforts rather than one continuous slope: the flatter links are your only chance to recover before the gradient bites back.

Pacing Notes

Over 31.2 km, discipline beats ambition every time. Anchor your effort to a sustainable percentage of your FTP — for a climb this long, most riders will want to hold a controlled tempo well below threshold, banking energy for the 17.7% spikes rather than burning it early. If you don't know your threshold, run the numbers through the FTP estimator before you go, then translate that figure into a target power you can defend for well over an hour. On the steep ramps, let cadence drop and power surge briefly, then reel it back in on the shallower sections. The 1632 m of vertical will punish anyone who redlines in the opening kilometres.

Gearing

Gear for the walls, not the average. The 5.22% mean is comfortable enough, but the 17.7% maximum is where compact-and-hope falls apart on tired legs after 31.2 km. A compact 34-tooth inner paired with a wide cassette is the sensible baseline: a 34×32 will get most fit riders over the steepest pitches, while a 34×34 buys you the extra margin that makes the difference late in a 1632 m ascent. If your knees or your legs are in doubt, size up — the bailout ratio you never use costs nothing, and the one you wish you had costs everything.

Summary

Col d'Arriel is a patience climb: 31.2 km, a steady-looking 5.22% average, and a summit at 2259 m that only rewards riders who respect the 17.7% ramps and the full 1632 m of vertical. Pace it low, gear it wide, and let the mountain come to you.

Length: 31.2 km
Average gradient: 5.22%
Max gradient: 17.7%
Start: 627 m
Summit: 2259 m
Net gain: 1632 m
Total ascent: 1577 m
Category: HC