Col du Basset

Overview

The Col du Basset is a hors catégorie climb, the hardest rating on the road, and it earns the label through sheer accumulation. Over 19.7 km the road lifts you from 753 m to a 2120 m summit, a net gain of 1367 m at an average gradient of 6.93%. The total ascent registers at 1326 m, meaning almost every metre of the climb is spent going up rather than dipping and recovering. This is a long, sustained effort where the challenge is less about a single savage ramp and more about holding a hard tempo for the better part of an hour. That said, the pitch tucked into these numbers is not gentle: a maximum gradient of 27.13% waits somewhere on the way up, and it will redefine your sense of what "average" means.

How the Gradient Unfolds

A 6.93% average across 19.7 km is a demanding baseline, but the spread between that average and the 27.13% maximum tells the real story. With net gain (1367 m) sitting above total ascent (1326 m), the climb is relentlessly upward, so the flatter stretches that would let you spin and breathe are rare. Expect long sections hovering near or above the average, punctuated by at least one severe ramp climbing toward that 27.13% peak. On a climb this length, the steep pitch does disproportionate damage: hit it with a full tank and you recover; hit it already fatigued and the remaining kilometres to 2120 m turn into damage control. Read the road, and treat every eased gradient as a chance to reset your breathing.

Pacing Notes

Pace this one off your sustainable power, not your ego. Your FTP is the anchor: on an HC climb of 19.7 km you will be at or just under threshold for a long time, so aim to sit comfortably below FTP on the sustained 6.93% sections and reserve a matchbook for the 27.13% wall. Going into the red early, before you have banked altitude toward the 1367 m gain, is the classic way to blow up. If you do not know your number, use the FTP estimator to set realistic targets before you start. On the steepest ramp, let cadence drop and power spike briefly rather than grinding to a stall — then settle straight back to your climbing tempo.

Gearing

For 19.7 km averaging 6.93% with a 27.13% maximum, gear for the wall, not the average. A compact 34-tooth chainring paired with a wide-range cassette is the sensible baseline: a 34×32 will handle the sustained gradient, but on a pitch approaching 27.13% you will be grateful for 34×34 or easier. If your legs or bike allow, going beyond 34×34 to a 36- or 40-tooth sprocket keeps your cadence alive on the steepest ramp and protects your knees over 1367 m of climbing. The goal is to spin the hard bits, not survive them at 40 rpm.

Summary

The Col du Basset is a true HC test: long, high, and steep in the places that count. Hold a disciplined tempo across the 19.7 km, respect the 27.13% ramp, and gear low enough to keep spinning all the way to 2120 m.

Length: 19.7 km
Average gradient: 6.93%
Max gradient: 27.13%
Start: 753 m
Summit: 2120 m
Net gain: 1367 m
Total ascent: 1326 m
Category: HC