Passo della Colla di Casaglia

Overview

Passo della Colla di Casaglia is a long, patient climb: 18.3 km of road that lifts you from a valley floor at 181 m to a summit at 863 m. That is a net gain of 682 m spread over the full distance, which works out to an average gradient of 3.72%. On paper that number reads gentle, and for much of the ascent it genuinely is — but the length is the real difficulty here. This is a category 2 climb, sitting in the middle of the scale below the fearsome hors catégorie (HC) and category 1 monsters, yet still demanding a sustained, honest effort rather than a short violent one.

How the Gradient Unfolds

The headline average of 3.72% hides the texture of the road. A total ascent of 666 m against a net gain of 682 m tells you the profile is not perfectly monotonic — there is a small amount of give-back, brief flatter or descending sections that let the road breathe between the harder pitches. The steepest recorded ramp hits 12.05%, more than three times the average, so you cannot simply lock into one rhythm and switch off. Expect long stretches close to that 3.72% mean, punctuated by steeper kicks that force you out of the saddle or down a couple of cogs. Because the summit sits at 863 m, the air thins only modestly, so the challenge stays muscular and cardiovascular rather than altitude-driven.

Pacing Notes

Over 18.3 km the smart approach is to ride to a target power rather than to feel. Anchor your effort to a percentage of your FTP — most riders can hold just below threshold for a climb of this duration, easing back on the flatter reprieves and accepting a short surge over the 12.05% ramp rather than blowing the whole effort to hold power there. If you are unsure of your number, run through the FTP estimator before you plan the ride so your pacing has a real target underneath it. Start conservatively: the 682 m of climbing rewards riders who arrive at the upper third with something left, not those who empty themselves in the opening kilometres.

Gearing

At 3.72% average you will not need bailout gears for most of the climb, but the 12.05% max is where a compact setup earns its keep. A 34-tooth inner ring paired with a 34×32 cassette is a sensible baseline for strong climbers, giving you a manageable low gear for the steepest ramp without spinning out on the flatter middle. If you tend to grind, or you are tackling this on tired legs at the end of a long day, step up to a 34×34 — the extra sprocket keeps your cadence high across the full 18.3 km and makes the steep pitches feel like an adjustment rather than an emergency.

Summary

Passo della Colla di Casaglia is a rhythm climb: long enough to test your patience and pacing, gentle enough on average to ride smoothly, with just enough steepness at 12.05% to keep you honest. Ride to power, gear for the ramps, and let the length do the rest.

Length: 18.3 km
Average gradient: 3.72%
Max gradient: 12.05%
Start: 181 m
Summit: 863 m
Net gain: 682 m
Total ascent: 666 m
Category: 2