Col d'Argentière

Overview

The Col d'Argentière is a long-haul category 1 climb that trades brutal steepness for sheer duration. Over 30.5 km it lifts you from a valley floor at 483 m to a summit of 1723 m — a net gain of 1240 m. The average gradient reads a modest 4.07%, but that headline number hides the real character of the climb: at this length, even a gentle-looking slope becomes a sustained test of patience, rhythm, and fuelling. This is a climb you settle into rather than attack.

How the Gradient Unfolds

Do the arithmetic and the shape becomes clear. A 4.07% average across 30.5 km is the definition of a "false flat that never ends" — long enough that a small percentage translates into a big total. The net gain of 1240 m is slightly larger than the total ascent figure of 1218 m, a 22 m difference that tells you the road is not a pure monotonic climb: there are short reprieves or minor dips where you briefly stop gaining height. The sting is the 10.18% maximum, more than double the average. Expect the ascent to alternate between long shallow drags where you can hold a steady tempo and sharper ramps that punch well above the mean before easing off again. Managing the difference between the 4.07% you plan for and the 10.18% you occasionally hit is the whole game here.

Pacing Notes

On a climb this long, discipline beats bravado. The smart approach is to ride the shallow sections just below threshold and reserve your matches for the steeper ramps toward 10.18%. Anchor your effort to your FTP: aim to sit comfortably under it on the long 4% drags so you have headroom when the gradient bites. If you do not know your current number, run the numbers through the FTP estimator before you commit to a target. With 1240 m of vertical to absorb, going out too hard in the first third is the classic error — the climb rewards riders who arrive at the steep pitches with legs still intact.

Gearing

Duration plus double-digit ramps means you want gearing that lets you spin, not grind. A compact 34-tooth inner chainring is the sensible starting point. Paired with a 34×32, most riders will keep a workable cadence on the 4.07% majority of the climb and survive the 10.18% pitches. If you are carrying fatigue, riding at a heavier weight, or simply prefer to protect your knees over 30.5 km, drop to a 34×34 for that extra bailout gear on the steepest ramps. The longer the climb, the more you will value a low gear you never quite need over a gear that runs out under you.

Summary

The Col d'Argentière is an endurance climb first and a gradient challenge second: 30.5 km, 1240 m of net gain, and a summit at 1723 m demand patience far more than raw power. Pace the 4.07% average conservatively, save something for the 10.18% ramps, and gear low. Get those three right and this category 1 giant becomes a long, satisfying rhythm rather than a battle.

Length: 30.5 km
Average gradient: 4.07%
Max gradient: 10.18%
Start: 483 m
Summit: 1723 m
Net gain: 1240 m
Total ascent: 1218 m
Category: 1