Col d'Aubisque

Overview

The Col d'Aubisque is an hors catégorie ascent, the hardest tier there is before the numbering system even begins. It runs 18.4 km from a valley floor at 467 m up to a summit sitting at 1711 m. That is 1244 m of net elevation gain, and 1226 m of total ascent — the near-identical figures telling you this is a relentlessly upward road with almost no relief thrown back down at you. The average gradient of 6.76% sounds civilised, but average is a liar on a climb this long: sustained double-digit pitches lurk inside it, with a maximum of 12.37%.

How the Gradient Unfolds

Think of the Aubisque as a long, honest grind rather than a wall. Over 18.4 km, a 6.76% average means you are climbing for well over an hour for most riders, and the road rarely lets you coast. The signature of an HC climb is the gap between the average and the max: here that gap runs from 6.76% up to 12.37%, so the steepest sections are close to double the mean. Those ramps are where the climb bites — you settle into the 6-to-7% rhythm, then a pitch nearly doubles the load under your wheels and forces a decision about whether to grind or drop a gear. With only 18 m separating net gain from total ascent, there are no meaningful descents to recover on. What goes up, stays up.

Pacing Notes

The Aubisque is won or lost on discipline in the first third. With 1244 m still to climb once you clear the lower slopes, riders who chase the early gradient pay for it on the steep ramps later. Anchor your effort to your FTP and hold something in reserve for the 12.37% sections rather than the 6.76% average. A good rule on an HC climb is to sit a touch below threshold on the shallower stretches so you have headroom when the road kicks up. If you do not know your current threshold, run the numbers through the FTP estimator before you plan your target power — pacing 18.4 km blind is how you blow up at 1500 m. Keep your cadence steady and let the steep ramps raise your effort, not your ego.

Gearing

For 18.4 km averaging 6.76% with pitches to 12.37%, gear for the steep sections, not the average. A compact 34-tooth inner chainring paired with a 34×32 will get most fit riders over the top, but on an HC climb of this length the smart move is a 34×34 for extra insurance on the ramps. The lower ratio lets you spin the 12.37% grades instead of muscling them, which protects your legs across the full 1244 m of climbing. If you are carrying luggage or riding late in a big day, the 34×34 stops being a luxury and becomes the difference between riding and walking.

Summary

The Col d'Aubisque is a genuine HC test: long, steadily steep, and unforgiving across all 18.4 km. Pace it below threshold early, gear low for the ramps, and respect the 1244 m of climbing between you and the summit.

Length: 18.4 km
Average gradient: 6.76%
Max gradient: 12.37%
Start: 467 m
Summit: 1711 m
Net gain: 1244 m
Total ascent: 1226 m
Category: HC