Colma Prabello

Overview

Colma Prabello is a climb that leaves no room for compromise. Over 9.6 km it averages a savage 10.7%, lifting you from a start elevation of 199 m to a summit at 1226 m. That is a net elevation gain of 1027 m, with 1012 m of total ascent packed into a road that almost never lets up. The category tells the whole story: HC, hors catégorie, the hardest rating on the scale before the numbers 1 through 4 begin. This is not a climb you drift up. It is one you survive, then remember.

How the Gradient Unfolds

A 10.7% average across 9.6 km is already the kind of figure that defines a rider's day, but averages hide the sting. The maximum gradient here reaches 21.28%, more than double the mean, which means the mellow stretches are few and the steep pitches are punishing. When a climb averages this high, there is precious little recovery terrain to hide in. Expect long walls where the road tilts into the teens and short, vicious kicks toward that 21.28% ceiling. The shape of Colma Prabello is relentless density: 1027 m of vertical gain compressed into under ten kilometres, so gravity is a constant companion rather than an occasional visitor.

Pacing Notes

On a climb this steep, pacing is everything. The single biggest mistake is chasing the early ramps and blowing past your threshold in the first kilometre, because there is no flat section ahead to bail you out. Anchor your effort to your FTP and treat the 10.7% average as a sustained-power problem rather than a series of sprints. On the 21.28% pitches, accept that your power will spike above threshold briefly — the key is settling back down immediately afterward rather than letting the effort snowball. If you do not know your numbers, run them through the FTP estimator before you commit, then build a target you can hold for the full 9.6 km. Climbing 1027 m at this gradient is a war of attrition, and patience in the opening third buys you a summit you can actually reach.

Gearing

Do not under-gear this one. With a 10.7% average and ramps to 21.28%, most riders will want the widest cassette they can bolt on. A compact 34-tooth chainring paired with a 34×32 low gear is a sensible floor, but on the steepest walls even that can leave your cadence crawling. If your derailleur allows it, step up to 34×34 for genuine breathing room on the 21.28% sections. The extra tooth or two of range is the difference between spinning and grinding to a halt across 1027 m of climbing. Bring easier gearing than you think you need.

Summary

Colma Prabello is a distilled HC challenge: short in distance, merciless in gradient, and unforgiving from bottom to top. Respect the 10.7% average, fear the 21.28% ramps, and gear low. Do that, and 1027 m of climbing become a summit worth the suffering.

Length: 9.6 km
Average gradient: 10.7%
Max gradient: 21.28%
Start: 199 m
Summit: 1226 m
Net gain: 1027 m
Total ascent: 1012 m
Category: HC