Colma del Bosco

Overview

Colma del Bosco is one of those climbs that leaves no room to hide. Over 7.8 km it averages 10.28%, a figure that would be a peak gradient on many lesser roads and here is simply the baseline. From a start elevation of 424 m the climb hauls you up to a 1230 m summit, a net gain of 806 m across a total ascent of 772 m. The steepest pitch bites at 19.88%. Add it all up and you have a fully-fledged HC ascent — hors catégorie, the hardest rating there is, sitting above categories 1 through 4. There is nothing casual about it.

How the Gradient Unfolds

The defining trait of Colma del Bosco is relentlessness. A 10.28% average over 7.8 km means there is no genuine recovery built into the road — where a friendlier climb hands you a flat shelf to spin out your legs, this one keeps the pressure constant. The gap between the 10.28% average and the 19.88% maximum tells you the story: the hardest ramps roughly double the average, so when the gradient spikes you feel it as an abrupt, near-1-in-5 wall rather than a gentle stiffening. That the net elevation gain (806 m) exceeds the total ascent (772 m) confirms the road climbs almost monotonically, with negligible descending to break the rhythm. Expect the pitch to sharpen and ease in waves, but never to let go entirely.

Pacing Notes

On a climb this steep and sustained, pacing is everything. The 7.8 km at 10.28% will likely take most riders well beyond a short threshold effort, so anchoring your pace to your FTP is the smart move. Ride the shallower opening sections a touch below FTP to bank a reserve, then accept that the 19.88% ramps will punch you briefly over threshold no matter how disciplined you are — that is unavoidable, so plan for it rather than panic. If you do not know your current number, estimate it first with the FTP estimator and set a realistic ceiling. The mistake here is going out hard on the lower slopes; with 806 m of climbing ahead, an early overreach compounds badly.

Gearing

Do not under-gear this one. With a 10.28% average and pitches to 19.88%, you want the lowest ratio you can sensibly fit. A compact 34-tooth chainring paired with a 34×32 cassette is the practical minimum for strong climbers, giving a near 1:1 ratio to grind the steady sections. Most riders will be far happier with 34×34, which buys real breathing room on the 19.88% ramps and lets you keep a survivable cadence rather than lurching in a mash. If your setup allows anything lower still, use it — spinning a small gear beats muscling a big one over 7.8 km this steep.

Summary

Colma del Bosco is a short but uncompromising HC climb: steep from the outset, steeper at its worst, and unforgiving of a poor pace. Respect the gradient, gear low, and let your FTP govern the effort.

Length: 7.8 km
Average gradient: 10.28%
Max gradient: 19.88%
Start: 424 m
Summit: 1230 m
Net gain: 806 m
Total ascent: 772 m
Category: HC