Col de Combe Blanche

Overview

Col de Combe Blanche is a long, patient climb rather than a violent one. Over 23.3 km it lifts you from a valley floor at 382 m to a summit of 1403 m, a net gain of 1021 m. The average gradient reads a modest 4.38%, which on paper looks almost benign — but distance is the real difficulty here. A category 1 rating is earned not by any single wall but by the sheer sustained effort of pedalling uphill for the better part of an hour. The total ascent of 1016 m sits just below the net figure, telling you the road climbs almost relentlessly with only trivial relief along the way.

How the Gradient Unfolds

The headline number to respect is the 13.16% maximum. That is nearly three times the average, so the climb is far from uniform. Expect the road to breathe: long stretches near or below the 4.38% mean that let you settle into rhythm, punctuated by steeper ramps that spike toward that double-digit maximum. Because net gain (1021 m) and total ascent (1016 m) differ by only 5 m, there is virtually no descending to recover on — every metre you lose you must immediately reclaim. The shape rewards riders who can hold a steady output and absorb the steep pitches without panic, then ease back onto the gentler grades to recover on the bike.

Pacing Notes

On a climb this long, discipline beats ambition. Your target effort should sit around threshold or just below — roughly your FTP if you intend to ride the whole 23.3 km near your limit, and comfortably under it if the summit is only a checkpoint. The classic error is torching your reserves on an early ramp toward the 13.16% max and paying for it across the remaining kilometres. If you do not know your threshold power, run the numbers through the FTP estimator before you commit to a pace. Meter your effort against the 4.38% average, spend a little extra on the steep sections, and claw it back on the shallower grades.

Gearing

Distance amplifies fatigue, so give yourself an easier gear than the 4.38% average suggests. A compact 34-tooth chainring paired with a 34×32 cassette covers most riders comfortably on the sustained middle grades. For the ramps that climb toward the 13.16% maximum, or if you are carrying fatigue from earlier in a ride, step up to a 34×34. That extra sprocket keeps your cadence alive on the steep pitches and protects your legs across the full 23.3 km rather than forcing you to grind.

Summary

Col de Combe Blanche is a test of sustained effort: long, steady, and unforgiving in its refusal to give anything back. Pace it against the average, respect the steep ramps, gear low, and the summit at 1403 m is well within reach.

Length: 23.3 km
Average gradient: 4.38%
Max gradient: 13.16%
Start: 382 m
Summit: 1403 m
Net gain: 1021 m
Total ascent: 1016 m
Category: 1