Alto de Cusirí

Overview

Alto de Cusirí is one of those climbs that redefines what your legs think they can endure. At 39 km long, it is a genuine hors catégorie test — the HC label reserved for climbs that sit beyond ordinary classification. From a base at 1457 m, the road grinds upward to a summit of 3473 m, a net elevation gain of 2016 m. The average gradient of 5.17% sounds almost civilized on paper, but stretched across 39 km it becomes a war of attrition. Add in a total ascent of 2110 m — more than the net figure, thanks to brief reprieves that force you to climb the same metres twice — and you have an effort measured in hours, not minutes.

How the Gradient Unfolds

Do not be seduced by the 5.17% average. Averages smooth over the story, and Cusirí's story is one of wild variance. The maximum pitch hits 15.23%, nearly triple the mean, which tells you the climb is not a metronome but a series of surges and lulls. The gap between the 2110 m of total ascent and the 2016 m of net gain reveals 94 m of climbing that gets given back somewhere along the way — small descents or false flats that let the road rear up again afterward. Expect long sustained ramps interrupted by steep kicks that spike toward that 15.23% ceiling. Reading the road ahead matters here: every visible pitch is a decision about whether to hold power or absorb the ramp.

Pacing Notes

On a climb this long, discipline beats bravado. The single most useful number you can bring is your FTP — your threshold power anchors every pacing decision across 39 km. Ride the shallower sections a touch below threshold to bank energy for the ramps toward 15.23%, where surging is unavoidable. If you do not know your threshold yet, run the numbers through the FTP estimator before you commit to a target. Remember too that the summit sits at 3473 m: thinner air late in the climb will quietly erode your ceiling, so a wattage that feels sustainable at the 1457 m base will feel heavier near the top. Pace for the whole 2016 m of gain, not the first hour.

Gearing

With 39 km at 5.17% average and spikes to 15.23%, gear for survival, not pride. A compact 34-tooth chainring is the baseline. Pair it with at least a 34×32 to keep a spinnable cadence on the sustained middle sections. But given the 15.23% pitches arriving deep into 2110 m of accumulated ascent, a 34×34 is the smarter insurance — that extra range is what keeps your knees intact and your cadence alive when fatigue and altitude compound. Choose the easier setup and you will rarely regret it on a climb this long.

Summary

Alto de Cusirí is a full-day objective: 39 km of climbing, 2016 m of net gain, and a summit at 3473 m thin enough to matter. Respect the 15.23% pitches, gear low, pace to your threshold, and let the mountain come to you.

Length: 39 km
Average gradient: 5.17%
Max gradient: 15.23%
Start: 1457 m
Summit: 3473 m
Net gain: 2016 m
Total ascent: 2110 m
Category: HC