Col du Grand Barme

Overview

The Col du Grand Barme is an HC (hors catégorie) monster, the hardest classification on the road. Over 24 km it hauls you from a start elevation of 592 m all the way to a 2263 m summit, a net elevation gain of 1671 m. The average gradient reads 6.97%, but that single figure hides a brutal truth: somewhere on this mountain the road tilts to 33.43%, a wall steep enough to stall all but the strongest riders. With 1633 m of total ascent packed into the profile, there is almost nowhere to hide.

How the Gradient Unfolds

Do not be fooled by the 6.97% average. A climb this long with a max of 33.43% is defined by its variance. The near-identical net gain of 1671 m and total ascent of 1633 m tell you the road climbs almost the entire way with barely any descending relief, so any easy stretch is bought back later with something far steeper. Expect long sustained ramps around the average, punctuated by pitches that spike well into the teens and beyond, culminating in that 33.43% maximum that will punish anyone who has spent their matches early. Break the 24 km into thirds and treat each one as its own effort; the shape here rewards patience and punishes ego.

Pacing Notes

On a climb this size, pacing is everything. Anchor your effort to your FTP and hold well below threshold for the opening kilometres — the summit at 2263 m is a long way off, and the steepest gradients arrive when your legs are already loaded. If you do not know your current threshold, run the numbers through the FTP estimator before you commit to a target. On the 33.43% pitch, forget power targets entirely: it becomes a traction-and-cadence survival problem, so approach it with momentum and a gear in reserve. Over 1671 m of climbing, riding two or three percent too hard early costs you dearly near the top.

Gearing

For an HC climb topping out at 33.43%, gear low and gear again. A compact 34-tooth chainring paired with a 34×32 cassette is the sensible baseline for the sustained sections around 6.97%, and most riders will want to go further. On the steepest ramps a 34×34 setup gives you the extra spin you need to keep the pedals turning without grinding to a halt. If your bike accepts an even wider range, take it — 24 km with a 33.43% wall is no place to be over-geared. Protecting your cadence protects your legs for the full 1671 m.

Summary

The Col du Grand Barme earns its HC label without argument: 24 km of climbing, an average of 6.97%, a summit at 2263 m, and a 33.43% maximum that redefines what "hard" means. Respect the distance, gear low, pace from the bottom, and the 1671 m of net gain becomes an achievement rather than a wrecking.

Length: 24 km
Average gradient: 6.97%
Max gradient: 33.43%
Start: 592 m
Summit: 2263 m
Net gain: 1671 m
Total ascent: 1633 m
Category: HC