Col du Saix

Overview

The Col du Saix is one of those climbs where the numbers do the talking, and every one of them is intimidating. Over 10.8 km it averages 9.02%, dragging you from a valley floor at 411 m up to a summit of 1387 m. That is 976 m of net elevation gain, with 952 m of total ascent packed into a climb that barely relents. Classified HC — hors catégorie, the hardest rating on the scale above categories 1 through 4 — the Saix earns the label honestly. A sub-1% difference between net gain and total ascent tells you almost the whole road tilts upward; there is nowhere to coast and recover.

How the Gradient Unfolds

An average of 9.02% is punishing on its own, but averages hide the teeth. With a maximum pitch of 32.2%, the Saix hurls ramps at you that are more than three and a half times steeper than its own mean. Those spikes are what break a rhythm. Because the difference between the 976 m net gain and the 952 m total ascent is so small, there are effectively no false flats or descents to exploit — the climb simply keeps rising for the full 10.8 km. Expect long stretches sitting near or above the 9% average, punctuated by savage kicks that push toward that 32.2% figure. Reading the road ahead and shifting early matters more here than on almost any other profile.

Pacing Notes

On a climb this steep and this long, discipline early is everything. Anchor your effort to your FTP rather than to how you feel in the opening kilometre, where fresh legs tempt you into a pace the remaining 10.8 km will not forgive. Aim to hold a steady, sustainable power on the 9.02% base gradient and accept that the ramps toward 32.2% will spike your effort well above threshold — let those surges pass, then settle back down rather than trying to hold that intensity. If you are unsure of your threshold number, run it through the FTP estimator before you commit to a target for the day. Getting your pacing anchor right is the difference between cresting the 1387 m summit strong and cracking with kilometres still to climb.

Gearing

Do not under-gear this one. With a 9.02% average sustained across 976 m of climbing and pitches touching 32.2%, generous ratios are not a luxury — they are survival. A compact 34-tooth chainring paired with a 34×32 cassette is the sensible minimum for strong riders, but on the steepest ramps even that will have you grinding at low cadence. Most riders will be far happier with a 34×34, giving you a genuine bailout gear to spin through the worst pitches while keeping your legs and back intact for the full 10.8 km. When in doubt, take the easier gear; the Saix rewards cadence over grit.

Summary

The Col du Saix is a true HC test: relentless, steep, and unforgiving from 411 m to 1387 m. Respect the gradient, gear low, pace to your threshold, and it becomes one of the most satisfying summits you can earn.

Length: 10.8 km
Average gradient: 9.02%
Max gradient: 32.2%
Start: 411 m
Summit: 1387 m
Net gain: 976 m
Total ascent: 952 m
Category: HC