Col de Lys

Overview

Col de Lys is a long, sustained category 1 climb that asks for patience more than punch. Over 18.1 km the road lifts you from a start elevation of 374 m to a summit at 1571 m — a net gain of 1197 m, with 1179 m of that arriving as pure ascent. The average gradient of 6.63% sounds moderate on paper, but at nearly 18.1 km in length it adds up to a genuine mountain effort. This is the kind of ascent where the clock, not the incline, becomes the real adversary. Only category HC climbs rank harder, and Col de Lys sits comfortably at the top of category 1.

How the Gradient Unfolds

The headline number is the 6.63% average, but averages hide the story. With a maximum gradient of 19.52%, this climb clearly banks steep, punishing pitches somewhere along its 18.1 km — nearly triple the average slope. Expect the effort to swing: stretches near or below the 6.63% mean where you can find rhythm, broken by ramps that spike toward that 19.52% ceiling and force you out of the saddle. Because the total ascent (1179 m) sits just under the net gain (1197 m), the profile is almost relentlessly upward, with little in the way of descending relief to recover on. Read the road ahead and save something for the walls.

Pacing Notes

On a climb this long, discipline wins. Set your effort to your sustainable threshold rather than chasing the steep sections, because 18.1 km leaves no room to bury yourself early. Anchor your pacing to your FTP: riding the shallower grades a touch below threshold buys you the headroom to survive the ramps toward 19.52% without blowing up. If you are unsure of your number, run the FTP estimator first, then translate that into a target power band for the full 1197 m of climbing. Fuel and drink on the easier pitches — the steep ones will not give you the chance.

Gearing

With ramps reaching 19.52% stacked onto 18.1 km of climbing, gearing is not the place to be brave. A compact 34-tooth chainring paired with a wide cassette is the sensible baseline. If you climb strongly and hold power well, a 34×32 will get most riders over the top with a little in reserve. But given the length and the near-20% maximum, most riders will be glad of a 34×34 — the extra sprocket keeps your cadence alive on the steepest walls and protects your legs across the full 1197 m of gain. When in doubt on a climb this sustained, choose the easier ratio.

Summary

Col de Lys is a long-haul category 1 test: 18.1 km of near-continuous climbing averaging 6.63%, with a sting of 19.52% and 1197 m separating start from summit. Pace it to threshold, gear it generously, and let the numbers — not the ego — set the tempo.

Length: 18.1 km
Average gradient: 6.63%
Max gradient: 19.52%
Start: 374 m
Summit: 1571 m
Net gain: 1197 m
Total ascent: 1179 m
Category: 1