Pas de Chaudin

Overview

Pas de Chaudin is a hors catégorie (HC) climb — the hardest rating on the road — and its numbers explain why. Over 17.8 km it averages 8.79%, dragging you from a start elevation of 803 m to a summit at 2370 m. That is 1567 m of net elevation gain, with a total ascent of 1508 m once the small pieces of respite are subtracted. There is no gentle warm-up here: an average approaching 9% held across nearly 18 km means the climb asks a serious, sustained effort from the first pedal stroke to the last.

How the Gradient Unfolds

The defining feature of Pas de Chaudin is consistency of difficulty rather than a single wall. With a net gain of 1567 m spread over 17.8 km, the road climbs roughly 88 m for every kilometre travelled — steep enough that the gradient rarely eases below a demanding pitch. Because the total ascent (1508 m) sits just below the net gain (1567 m), you can expect almost no genuine descending or flat recovery inside the climb; nearly every metre travelled is a metre gained. Practically, that means the 8.79% average behaves like a floor as much as a mean. Where a climb with false flats lets you spin and recover, Chaudin keeps the pressure on, so the back half — as you push through the thin air above 2000 m toward the 2370 m summit — is where the accumulated fatigue bites hardest.

Pacing Notes

On a climb this long and this steep, pacing discipline decides your day. Anchor your effort to a percentage of your FTP: for most riders, a sustained climb of roughly 17.8 km falls into a threshold-adjacent zone, so starting a touch below FTP protects you against blowing up in the final kilometres near the summit. If you don't know your threshold, run the numbers through the FTP estimator before you commit. Aim to reach the halfway point feeling like you are holding back slightly — the altitude gain toward 2370 m will erode your ceiling, and negative-splitting an 8.79% average is far kinder than fading. Keep cadence up and effort even; surges are expensive when there's no flat to recover on.

Gearing

For a 17.8 km climb averaging 8.79%, gear low and gear generously — spinning preserves the legs across such a long sustained effort. A compact 34-tooth chainring paired with a wide cassette is the sensible baseline. A 34×32 is workable for strong climbers who can hold a solid cadence at threshold, but on a gradient this relentless most riders will be grateful for a 34×34, which gives you an easier ratio to keep the pedals turning when fatigue sets in on the upper slopes toward the 2370 m summit. If your bike accepts an even larger sprocket, don't be proud about using it.

Summary

Pas de Chaudin is a true HC test: long, unwaveringly steep, and topping out in high, thin air. Pace it conservatively, gear it low, and respect the sustained 8.79% — the climb rewards patience and punishes bravado.

Length: 17.8 km
Average gradient: 8.79%
Max gradient: n/a
Start: 803 m
Summit: 2370 m
Net gain: 1567 m
Total ascent: 1508 m
Category: HC