Col de la Croix de Fer

Overview

The Col de la Croix de Fer is a hors catégorie (HC) climb, the hardest rung on the categorisation ladder before the numbered climbs — 1, 2, 3, and 4 — begin. It stretches 28.8 km from a start elevation of 484 m to a summit at 2061 m. That gives a net elevation gain of 1577 m at an average gradient of 5.48%. The number that tells the real story, though, is the total ascent: 1634 m. Because the road climbs 1634 m while only netting 1577 m, you know the profile isn't a clean ramp. There are dips built in — sections where you give back a little altitude before clawing it back again.

How the Gradient Unfolds

At almost 29 km, this is an endurance climb rather than an explosive one. A 5.48% average across that distance is deceptive: the 57 m gap between total ascent (1634 m) and net gain (1577 m) means the climb rolls. Wherever the road tips downward or flattens, the pitches that follow must be steeper than the average to keep the overall figure at 5.48%. Expect stretches noticeably above the mean, separated by false flats and short descents that break your rhythm rather than your legs. Reading the climb as a single steady effort is a mistake — treat it as a sequence of sustained blocks stacked back to back over 28.8 km.

Pacing Notes

Over a climb this long, pacing discipline decides everything. Anchor your effort to your FTP and hold a wattage you can sustain for well over an hour — the summit at 2061 m is a long way from the 484 m start. If you don't know your number, run the FTP estimator before you commit to a target. On the rolling sections, resist surging into every rise; let the downhills and flats be genuine recovery so the 1634 m of total climbing doesn't drain you before the top. Steady is fast here.

Gearing

For 28.8 km at 5.48% with steeper-than-average ramps mixed in, gear for the long haul, not the flats. A compact chainring paired with a wide-range cassette is the sensible baseline. A 34×32 will get most fit riders up the sustained pitches, but on a climb that racks up 1634 m of ascent, a 34×34 buys you a lower cadence-saving bailout for the steepest kicks and tired legs late on. Err toward the easier ratio — spinning 34×34 costs nothing on the mellow sections and rescues you on the hard ones.

Summary

The Croix de Fer is a patience climb: 28.8 km, an HC rating, and a rolling profile that hides genuinely steep pitches inside a modest 5.48% average. Pace to your FTP, gear low, and respect the full 1634 m of climbing to 2061 m.

Length: 28.8 km
Average gradient: 5.48%
Max gradient: n/a
Start: 484 m
Summit: 2061 m
Net gain: 1577 m
Total ascent: 1634 m
Category: HC