Alto de Chia

Overview

Alto de Chia is a hors catégorie climb, the hardest rung on the classification ladder, and it earns the label the honest way: through sheer duration. Over 21.1 km the road lifts you 1365 m, from a start elevation of 1483 m to a summit at 2848 m. The average gradient is 6.48%, which sounds civil on paper but hides both the length and the altitude. By the top you are riding at nearly 2848 m, where thinner air quietly steals watts you did not know you were spending.

This is a climb of patience. There is no single wall that defines it; instead, the challenge is the accumulation of steady effort across a distance most riders would consider a full ride on its own.

How the Gradient Unfolds

At 6.48% average across 21.1 km, Alto de Chia sits in that punishing middle band, steep enough to demand real work, shallow enough that you never coast. But the average smooths over the sharp edges. The maximum gradient hits 15.58%, more than double the average, so somewhere on this ascent the road roughly doubles in pitch and asks for a violent change of rhythm.

Expect the profile to breathe: stretches near the 6.48% mean, softer segments that let you recover, and pinches climbing toward that 15.58% ceiling. The gap between the 6.48% average and the 15.58% peak is the story here, that 9.1-point swing is where pacing discipline is won or lost.

Pacing Notes

On a climb this long, pacing is everything. The total ascent of 1363 m and net gain of 1365 m mean you are working continuously for well over an hour for most riders, so ride to your sustainable ceiling, not your ego. Anchor your effort to your FTP: on the sustained 6.48% sections, hold a power you could defend for the full 21.1 km, and bank a little in reserve for the 15.58% ramps.

If you are unsure where your ceiling sits, run the numbers through the FTP estimator before you commit. Then let altitude respect itself, as you climb toward 2848 m, the same power will simply feel harder, so plan to give back a fraction near the top rather than blowing apart chasing a flatland number.

Gearing

For a 21.1 km HC ascent averaging 6.48% with ramps to 15.58%, gear for the worst pitch, not the average. A compact 34-tooth inner chainring is the sensible starting point. Pair it with at least a 34×32, which keeps your cadence alive on the sustained middle sections.

But given the 15.58% maximum and the altitude penalty near 2848 m, most riders will be happier with a 34×34. That extra sprocket is cheap insurance: it lets you spin rather than grind through the steepest ramp, preserving your legs for the long haul above. When a climb is this long, the wider ratio almost always pays for itself.

Summary

Alto de Chia is a distance-and-altitude test rather than a wall: 21.1 km of near-relentless 6.48% climbing, spiked by a 15.58% maximum, topping out in thin air at 2848 m. Gear generously, pace to your ceiling, and respect the length.

Length: 21.1 km
Average gradient: 6.48%
Max gradient: 15.58%
Start: 1483 m
Summit: 2848 m
Net gain: 1365 m
Total ascent: 1363 m
Category: HC