Col Fussy

Overview

Col Fussy is a climb that does not negotiate. Over 21.4 km it averages a brutal 9.21%, hauling you from a start elevation of 344 m to a 2319 m summit. That is 1975 m of net elevation gain, with 1946 m of total ascent packed almost entirely into one relentless upward line. There is no rolling profile here to hide behind — the numbers describe a wall that simply keeps climbing.

Rated HC, or hors catégorie, this is the hardest classification on the scale, sitting above categories 1, 2, 3, and 4. An HC label is reserved for climbs that overwhelm the usual metrics, and a near-double-digit average sustained across more than twenty kilometres earns it comfortably.

How the Gradient Unfolds

The defining feature of Col Fussy is the gap between its average and its maximum. A 9.21% mean is already severe over 21.4 km, but the 23.87% max gradient tells you the road pitches to nearly a wall in places — more than 14 percentage points steeper than the average.

Because net gain (1975 m) sits above total ascent (1946 m), there is effectively no descending relief across the whole climb; every metre is spent going up. That means the steep ramps toward 23.87% are not offset by recovery flats. When the road kicks, you absorb it and keep grinding. Expect the gradient to swing hard around that 9.21% mean, with the cruelest sections demanding you stay seated and patient rather than trying to muscle over them.

Pacing Notes

On a climb this long and steep, pacing is everything. Anchor your effort to your FTP and hold a sustainable percentage of it rather than chasing the early slopes. At 9.21% average over 21.4 km, going too deep in the first few kilometres guarantees you blow before the 2319 m summit.

If you are unsure of your threshold, run the numbers through the FTP estimator before you commit to a target. Treat the 23.87% ramps as short over-threshold surges, then settle straight back to your climbing pace. With 1975 m of net gain ahead, discipline in the opening third pays off across the final push to the top.

Gearing

Do not under-gear this one. For most riders a compact 34-tooth inner ring paired with a wide cassette is the right call. A 34×32 is the sensible minimum for a fit rider comfortable spinning a steep 9.21% average, but given the 23.87% pitches and the sheer 21.4 km length, a 34×34 gives you the extra cadence to survive the worst ramps without wrecking your legs. If your setup allows anything larger at the back, take it — spinning up 1946 m of ascent beats grinding it.

Summary

Col Fussy is an uncompromising HC test: long, steep, and relentless from 344 m all the way to 2319 m. Respect the 9.21% average, brace for the 23.87% max, gear low, and pace to your threshold. Do that, and 1975 m of climbing becomes a summit worth earning.

Length: 21.4 km
Average gradient: 9.21%
Max gradient: 23.87%
Start: 344 m
Summit: 2319 m
Net gain: 1975 m
Total ascent: 1946 m
Category: HC