Col Basset

Overview

Col Basset is a genuine high-mountain objective: 29 km long, averaging 5.49%, and rated HC (hors catégorie), the hardest category above 1, 2, 3 and 4. It begins at 823 m and finishes at 2413 m, a summit high enough that thinning air becomes part of the challenge. The net elevation gain is 1590 m, while the total ascent measures 1592 m — the tiny 2 m difference tells you this is essentially a relentless, one-way climb with barely a metre given back along the way.

How the Gradient Unfolds

The headline average of 5.49% understates the character of this ascent. A climb this long rarely holds a single steady grade, and Col Basset is proof: the max gradient hits 29.6%, a wall roughly five and a half times steeper than the average. That spread between 5.49% and 29.6% is the whole story here. Expect long stretches that sit comfortably below the average — sections where you can find a rhythm — punctuated by sharp ramps that spike far into double digits. Because the total ascent (1592 m) so nearly matches the net gain (1590 m), there are effectively no descents to recover on. Every kilometre you climb is a kilometre banked, but also a kilometre without respite.

Pacing Notes

Over 29 km and 1590 m of gain, pacing is everything. Ride the first two-thirds well within yourself — the summit at 2413 m is where the climb is decided, not the lower slopes. Anchor your effort to a percentage of your FTP rather than to how you feel early on, because the opening kilometres at or below 5.49% can flatter you into going too hard. If you do not know your number, the FTP estimator will give you a working figure to plan around. Save headroom for the 29.6% max ramp: on a pitch that steep, staying seated and spinning is often impossible, and a brief, controlled surge out of the saddle costs less than grinding to a near-standstill. Above 2000 m, altitude quietly trims your ceiling, so the power you can sustain near the top will be lower than the same effort felt at 823 m.

Gearing

Gear for the wall, not the average. A 29.6% max gradient will overwhelm any setup built only for the 5.49% mean, so bring your easiest realistic ratios. For most riders a compact 34-tooth front with a 34×32 low gear is the sensible starting point on an HC climb of this length. If your legs or the day are anything less than perfect over 1590 m of gain, drop to 34×34 — the extra sprocket is cheap insurance on the steepest ramps and keeps your cadence high enough to protect your legs for the full 29 km.

Summary

Col Basset asks for patience, discipline and honest gearing. Nearly 29 km of near-continuous climbing to 2413 m, with a savage maximum pitch, makes it a true HC test rewarded by its high summit.

Length: 29 km
Average gradient: 5.49%
Max gradient: 29.6%
Start: 823 m
Summit: 2413 m
Net gain: 1590 m
Total ascent: 1592 m
Category: HC