Col Dazalou

Overview

Col Dazalou is a long haul. At 29.8 km with an average gradient of 4.79%, it earns a category-1 rating — one rung below hors catégorie, and still far harder than most riders bargain for. You start at 595 m and finish at 2022 m, a net gain of 1427 m. The total ascent of 1369 m sits just below the net figure, which tells you the road climbs almost relentlessly upward with only the faintest respite along the way. This is a climb defined by duration rather than sheer steepness: the challenge is holding a rhythm for the better part of an hour or more, not surviving a single wall.

How the Gradient Unfolds

The headline number — 4.79% average — is gentle on paper, but averages flatten the truth of a climb this long. Spread across 29.8 km, that mean gradient hides ramps that bite to 14.96%, more than three times the average. Because the total ascent (1369 m) is only slightly under the net gain (1427 m), there is very little descending mixed in; the road simply tilts up, eases, and tilts up again. Expect long stretches near the average that lull you into comfort, then sharper kicks toward the max that force you out of the saddle. Riders who ration effort across the full 29.8 km fare best.

Pacing Notes

On a climb of this length, pacing is everything. The smartest approach is to ride the shallow sections at a controlled effort and save headroom for the ramps toward 14.96%. Anchor your effort to your FTP: aim to sit just below threshold on the average-gradient stretches so the steep pitches don't blow you apart. Over 1427 m of climbing, a few percent too hard early compounds into a very long final third. If you don't know your threshold, plug your numbers into the FTP estimator before you go, then set a wattage ceiling and hold to it through the easier grades.

Gearing

Gear for the ramps, not the average. A 34×32 bottom gear is a sensible baseline for the 4.79% mean, but the 14.96% max is where a shortfall hurts. For most riders tackling all 29.8 km, a 34×34 is the wiser choice — that extra sprocket lets you spin the steep pitches at a cadence your legs can sustain over 1427 m of gain rather than grinding them at low RPM. If your knees or fitness are in question, err toward 34×34; you can always ride an easy gear hard, but you can't invent one you didn't bring.

Summary

Col Dazalou rewards patience and punishes bravado. It is long, steady, and occasionally steep, a category-1 test where holding your rhythm from 595 m to 2022 m matters more than any single ramp. Come with the right gearing, a disciplined effort, and respect for the distance.

Length: 29.8 km
Average gradient: 4.79%
Max gradient: 14.96%
Start: 595 m
Summit: 2022 m
Net gain: 1427 m
Total ascent: 1369 m
Category: 1