Colláu

Overview

Colláu is a long category 2 climb that rewards patience and punishes overconfidence. Across 17.9 km it averages a modest 4.39%, lifting you from a 773 m start to a 1561 m summit — a net elevation gain of 788 m. On paper those numbers read as a steady tempo effort, the kind of climb you can settle into and grind out. The catch is the 20.9% max gradient, a wall steep enough to reshape how you plan the entire ascent. With a total ascent of 840 m, there is also a small amount of up-and-down mixed in, so the profile is not a single clean incline. Treat the average as a lie you tell yourself at the bottom, and the maximum as the truth waiting somewhere above.

How the Gradient Unfolds

The 4.39% average is a blended figure across nearly 18 km, which means large stretches sit well below it to make room for the pitches that spike far above. That gap between 4.39% and 20.9% is the defining feature of Colláu. Expect shallow, almost rolling sections where you can breathe, spin, and eat — punctuated by ramps that force you out of the saddle and into damage control. The difference between the 840 m total ascent and the 788 m net gain confirms there are brief downhills or false flats that break the rhythm, so you rarely find one sustained cadence for long. Read the road ahead constantly: the danger is arriving at a 20.9% wall carrying too much speed-debt and no gears in reserve.

Pacing Notes

On a climb this long, discipline early is everything. Hold your effort just under threshold on the gentle kilometres and save your matches for the steep ramps, where power demand can double in a heartbeat. Anchor your pacing to your FTP: aim to sit comfortably below it on the 4.39% stretches so you have headroom to surge over the 20.9% pitches without blowing apart. If you don't know your current number, run the FTP estimator before you ride so your targets reflect real fitness rather than optimism. Because the summit sits at 1561 m, factor in thinner air near the top — the last portion of the 788 m gain will feel harder than the raw gradient suggests.

Gearing

Gear for the wall, not the average. A 20.9% max on a climb approaching 18 km makes low-range gearing non-negotiable if you want to keep pedalling instead of paper-boying across the road. A compact 34-tooth chainring paired with a 34×32 low is a sensible minimum for most riders, giving you a survivable cadence on the steepest ramps. If you have the fitness of a diesel rather than a sprinter, or you simply want insurance for a long day, go one step further to 34×34. That extra sprocket costs almost nothing on the shallow sections and buys real relief when the gradient hits its ceiling.

Summary

Colláu is a deceptive category 2: long, mostly moderate, and hiding real teeth in its steepest pitch. Pace the easy kilometres conservatively, gear low, and respect the 20.9% ramp, and the 788 m of climbing to 1561 m becomes a satisfying day rather than a survival exercise.

Length: 17.9 km
Average gradient: 4.39%
Max gradient: 20.9%
Start: 773 m
Summit: 1561 m
Net gain: 788 m
Total ascent: 840 m
Category: 2