Col d'Ars

Overview

Col d'Ars is a hors catégorie climb that earns its rating without any need for embellishment. Over 19.5 km the road gains 1765 m net, lifting you from a start elevation of 590 m to a 2355 m summit. The average gradient of 9.06% is the number that should command your respect: an HC label is often about length, but here it is about relentless, sustained steepness held over nearly twenty kilometres. With a total ascent of 1724 m across the effort, there is almost no reprieve — what you climb, you keep.

How the Gradient Unfolds

The defining feature of Col d'Ars is not a single wall but the refusal of the road to ease. A 9.06% average over 19.5 km means that if the climb were uniform, you would face that pitch from the first pedal stroke to the last. It is not uniform — the max gradient of 21.44% tells you there are ramps that more than double the average, and every ramp above the mean must be balanced by a shallower stretch elsewhere. Those shallower sections are your only recovery, and on a climb this steep they rarely fall below the point where you can truly rest. The 1765 m of net gain arriving over 1724 m of total ascent confirms how little descending punctuates the profile: this road goes up and stays up.

Pacing Notes

On a climb of this magnitude, pacing is survival. The 9.06% average will pull you toward your limit involuntarily on the steep pitches, so the discipline lies in holding back on the shallower ground rather than pushing on the walls. Ride to your FTP and treat the 21.44% ramps as brief overshoots you accept, not efforts you chase. Because the summit sits at 2355 m, expect thinner air in the final kilometres to shave a little from your sustainable power — bank effort early rather than late. If you are unsure of your number, run the FTP estimator before you commit to a target, then subtract a margin for the altitude and the sheer duration of 19.5 km of climbing.

Gearing

Gear for the walls, not the average. A compact 34-tooth chainring paired with a 32-tooth cassette (34×32) is the sensible floor for Col d'Ars, and even that will feel marginal when the road tips toward 21.44%. Most riders will be far happier with 34×34, which gives you the low end to keep the cranks turning through the steepest ramps without grinding to a standstill. On a 19.5 km climb averaging 9.06%, a cadence you can hold for over an hour matters more than a gear you can only survive for a minute — choose the easier ratio and spin.

Summary

Col d'Ars is a genuine test: long, unremittingly steep, and topping out high enough that altitude joins the fight. Respect the average, gear for the max, and pace for the full 19.5 km.

Length: 19.5 km
Average gradient: 9.06%
Max gradient: 21.44%
Start: 590 m
Summit: 2355 m
Net gain: 1765 m
Total ascent: 1724 m
Category: HC