Col d'Ollomont

Overview

The Col d'Ollomont is an HC climb — hors catégorie, the hardest rung on the scale before you even reach category 1. The numbers explain the rating without any embellishment: 18.2 km of climbing at a 7.37% average gradient, lifting you from a start elevation of 588 m to a summit at 1927 m. That is 1339 m of net elevation gain, with 1311 m of total ascent logged along the way. Nearly the entire climb is spent going up, and rarely gently.

How the Gradient Unfolds

A 7.37% average across 18.2 km is the headline, but averages flatten out the story. On a climb this long, the mean gradient is best read as a promise of relentlessness rather than a single fixed pitch. Because the total ascent of 1311 m sits just below the net gain of 1339 m, there is almost no descending or false-flat relief mixed in — what you climb, you keep. Expect long stretches hovering around that 7.37% figure, interrupted by ramps that pull harder and short passages that ease off just enough to let you reset. Plan your effort around the assumption that the road is always tilting upward, and treat any softer section as a bonus rather than a scheduled rest.

Pacing Notes

On a sustained 18.2 km at 7.37%, pacing is everything — this is a climb ridden by the numbers, not by feel. Anchor your effort to your FTP and hold a steady, repeatable output rather than surging on the steeper ramps. A common approach is to target a percentage of threshold you know you can sustain for the full duration of the ascent, which on a climb of this length will be measured in tens of minutes, not a handful. If you are unsure where your threshold sits, run the numbers through the FTP estimator before you commit, then ride the first few kilometres deliberately conservatively. The 1339 m of climbing ahead punishes an early overcook far more than a cautious opening.

Gearing

For an HC climb this long and this steep, gear for the summit, not the start. A compact 34-tooth inner ring paired with a wide-range cassette is the sensible baseline. A 34×32 will get most fit riders up the steady 7.37% sections, but on an 18.2 km grind at this average — with ramps that bite harder than the mean — a 34×34 gives you the extra bailout to keep your cadence up and your legs turning over when fatigue sets in near the 1927 m summit. If your bike accepts it, the 34×34 is the safer choice; carrying spare gear over 1339 m of vertical costs you nothing and buys you a lot.

Summary

The Col d'Ollomont is a proper HC test: 18.2 km at a 7.37% average, 1339 m of net gain from 588 m to 1927 m, with almost no respite built into the total ascent. Pace it by your threshold, gear for the top, and respect the length.

Length: 18.2 km
Average gradient: 7.37%
Max gradient: n/a
Start: 588 m
Summit: 1927 m
Net gain: 1339 m
Total ascent: 1311 m
Category: HC