Abra del Acay

Overview

Abra del Acay is a climb defined by the sky it reaches into. Over 23.1 km it lifts you from an already lofty 3919 m to a summit of 4951 m — a net gain of 1032 m at a modest-sounding average of 4.47%. On paper that gradient reads gentle, the kind of slope you might spin over without a second thought. In practice, every one of those 23.1 kilometres is ridden in thin air where oxygen is scarce and recovery is slow. This is a Category 1 climb not because the road rears up, but because it simply refuses to end, and it does so higher than almost anywhere a bike is ridden.

How the Gradient Unfolds

The story here is one of relentless consistency rather than dramatic ramps. With a 4.47% average spread across 23.1 km, the road tilts up at a rhythm you can settle into — but it rarely offers a true break. The maximum pitch touches 10.17%, more than double the average, so there are stretches that bite. The gap between total ascent of 1024 m and net gain of 1032 m tells you the profile is almost purely upward: there is essentially no descending or false flat to coast through. What goes up here stays up. Expect long, steady drags punctuated by the occasional steeper kick toward that 10.17% ceiling.

Pacing Notes

At this altitude, your usual power numbers lie to you. The thin air above 3919 m robs you of the top end, so pacing by feel and by your FTP becomes essential — but treat that threshold figure as a ceiling you rarely approach, not a target. Because the climb runs a full 23.1 km, going out even slightly too hard compounds badly; there is no flat to recover on and no oxygen to bail you out. Ride the lower half well within yourself and save something for the final push to 4951 m. If you are unsure of your threshold before committing to a climb this long, run the numbers through the FTP estimator first and build your target watts from there.

Gearing

Even though 4.47% average is not steep, the altitude effectively makes every gradient feel harder, so gear as if the climb were tougher than the math suggests. A compact 34-tooth chainring paired with a wide cassette is the sensible foundation. A 34×32 will get most riders over Abra del Acay, but given the 23.1 km length and the 10.17% maximum arriving when you are already oxygen-starved, a 34×34 buys you a spinnable escape gear that protects your legs and your breathing. When in doubt at this height, choose the easier ratio — cadence is your ally against thin air.

Summary

Abra del Acay is an endurance and altitude test dressed up as a moderate climb. The gradient never overwhelms, but the combination of 23.1 km of continuous ascent and a summit near 4951 m makes it a genuine Category 1 challenge. Pace it patiently, gear it generously, and respect the air.

Length: 23.1 km
Average gradient: 4.47%
Max gradient: 10.17%
Start: 3919 m
Summit: 4951 m
Net gain: 1032 m
Total ascent: 1024 m
Category: 1