Col du Lausfer

Overview

The Col du Lausfer is an HC climb — hors catégorie, the hardest rating on the scale before you drop down to categories 1, 2, 3 and 4. Everything about it is oversized. It runs 24.8 km from base to top, gaining 1685 m of net elevation as the road lifts you from 664 m all the way to a 2349 m summit. The average gradient sits at 6.81%, but that number hides a maximum pitch of 16.99%, so this is not a climb you settle into and forget. It is long enough to be a full endurance effort and steep enough in places to blow apart a poorly judged pace.

How the Gradient Unfolds

A 6.81% average across 24.8 km is deceptively civil on paper. The reality is a climb of two personalities. Long stretches sit near or just under the average, letting you find a rhythm — and then the road rears up toward that 16.99% ceiling, more than double the average. Those spikes are where the damage is done. With 1685 m of net gain but 1661 m of total ascent, the climb is almost entirely one-directional: there is essentially no free-rolling relief, no meaningful descents to recover your legs. Every metre of altitude you take on, you keep. Treat the mellow sections as your chance to bank energy before the next wall.

Pacing Notes

On a climb this long, pacing is the whole game. Your target should be a sustainable effort anchored to your FTP — over 24.8 km, going even slightly too hard early will cost you far more than it saves. Aim to hold the flatter grades comfortably below threshold so you have headroom when the gradient jumps toward 16.99%, where power spikes are unavoidable. If you do not know your threshold number, run it through the FTP estimator before you plan the day. Remember the summit sits at 2349 m: thinner air near the top will quietly shave watts off whatever you could produce at the 664 m base, so leave a little in reserve for the final kilometres.

Gearing

Gear for the steep pitches, not the average. With ramps reaching 16.99% at the end of a 24.8 km effort, you want a cassette that lets you keep cadence up when your legs are already deep into 1685 m of climbing. A compact 34-tooth chainring paired with a 34×32 is the sensible floor here for most riders. If you know you fade late, or you are carrying any extra weight, step up to a 34×34 — that extra sprocket is cheap insurance against grinding to a walking-pace slog on the worst ramps. Spinning a small gear will always beat mashing a big one on an HC climb.

Summary

The Col du Lausfer earns its HC billing honestly: 24.8 km of near-relentless climbing, a 6.81% average masking 16.99% ramps, and 1685 m of net gain to a high, thin-aired summit. Pace it patiently, gear it generously, and respect the length.

Length: 24.8 km
Average gradient: 6.81%
Max gradient: 16.99%
Start: 664 m
Summit: 2349 m
Net gain: 1685 m
Total ascent: 1661 m
Category: HC