Alto Guanacas

Overview

Alto Guanacas is an hors catégorie (HC) climb in Colombia that asks a serious question of your legs: 20.1 km of sustained uphill at an average gradient of 7.16%, hauling you from a start elevation of 1107 m to a summit at 2548 m. That is 1441 m of net elevation gain, with 1402 m of total ascent — meaning the road climbs almost relentlessly, giving back very little on the way up. With a maximum gradient of 15.46%, this is a climb that combines the length of a mountain pass with pitches steep enough to break your rhythm if you are careless. HC is the hardest category on the scale (ahead of 1, 2, 3, and 4), and Alto Guanacas earns the label honestly through raw duration and vertical.

How the Gradient Unfolds

The defining trait here is consistency. Across 20.1 km, the difference between the net gain of 1441 m and the total ascent of 1402 m is negligible — the road barely descends, so you are climbing essentially the entire way. At 7.16% average, expect long stretches where the gradient sits close to that figure and rarely lets you coast. The 15.46% maximum is more than double the average, so the pain is not evenly distributed: there are ramps where the road kicks well beyond a sustainable pace, likely clustered rather than spread out. Between them, the climb settles back toward its 7% baseline, which is demanding but repeatable. Read the road ahead and treat the steep sections as isolated efforts, not the new normal.

Pacing Notes

On a climb this long, pacing is everything. A 20.1 km effort at 7.16% will take most riders well over an hour, so anchor your intensity to your FTP rather than how you feel in the first kilometre. Sitting just below threshold on the steady sections leaves headroom to absorb the 15.46% ramps without redlining. If you do not know your threshold, run your recent numbers through the FTP estimator before you commit to a pace. The goal across 1441 m of climbing is to arrive at the steep pitches with something in reserve — go out too hard on the lower slopes and the back half of the ascent will punish you.

Gearing

For an HC climb of this length and steepness, gear low and gear generously. A compact 34-tooth chainring is the sensible front. Pairing 34×32 gives most riders enough range to spin the 7.16% average comfortably, but on the 15.46% maximum pitches — after more than an hour of climbing toward 2548 m — that ratio can feel tall. If you have the option, fit 34×34 for extra security on the steepest ramps and the fatigued final kilometres. The lower gear lets you protect cadence and save your knees over 1402 m of ascent. When in doubt on a climb like this, err toward the easier ratio.

Summary

Alto Guanacas is a true HC test: long, steep, and almost uninterrupted, with a summit at high altitude and a maximum pitch that demands respect. Pace to your threshold, gear low, and let the 20.1 km come to you.

Length: 20.1 km
Average gradient: 7.16%
Max gradient: 15.46%
Start: 1107 m
Summit: 2548 m
Net gain: 1441 m
Total ascent: 1402 m
Category: HC