Alto de Carrasposo

Overview

Alto de Carrasposo is a hors catégorie climb that gives you nowhere to hide. Over 12.5 km it averages a punishing 12.17%, dragging you from a start elevation of 1921 m to a summit of 3442 m. That is a net elevation gain of 1521 m, with 1589 m of total ascent once the small dips and recoveries along the way are counted. The difference between those two figures — 68 m — tells you this is a relentlessly upward road, not a rolling one. There is very little false flat to bank a rest on.

At 3442 m the summit sits high enough that thin air becomes a real factor. The HC rating here is fully earned: length, gradient, and altitude all compound.

How the Gradient Unfolds

A 12.17% average across 12.5 km is severe on its own, but the max gradient of 35.18% is what defines the climb's character. Ramps of that steepness are not sustained walls — they are short, brutal pitches that spike well above the mean and force sudden surges of effort. Expect the road to oscillate: stretches near the 12% average punctuated by kicks that lurch toward the low-to-mid 30s.

With only 68 m separating total ascent from net gain, there are no meaningful descents to reset your legs. Every metre of the 1521 m gain is paid for going up. Treat the steepest ramps as the crux and everything else as the place to recover just enough to survive the next one.

Pacing Notes

On a climb this long and steep, pacing is everything. Anchor your effort to your FTP and resist the temptation to chase the early ramps — 12.5 km at 12.17% will expose any overcooked start. On the 35.18% pitches your power will spike above threshold whether you like it or not, so build a buffer on the shallower sections by staying comfortably below FTP there.

Altitude matters: at 3442 m your sustainable power drops, so the FTP you rode in the valley is not the FTP you will hold near the summit. Plan for a fading ceiling over the final kilometres. If you are unsure of your number, run the FTP estimator before you commit to a target and pace conservatively for the last third.

Gearing

Do not under-gear this one. With a 12.17% average and ramps to 35.18%, most riders will want the widest range they can fit. A compact 34-tooth chainring paired with a 34×32 is a sensible floor, but given the sustained pitch and the altitude sapping your power near 3442 m, a 34×34 is the safer choice for keeping your cadence out of the danger zone on the steepest ramps. If your setup allows an even larger cassette or a sub-compact ring, take it — spinning a low gear at 3442 m beats grinding to a standstill on a 35% wall.

Summary

Alto de Carrasposo is an uncompromising HC ascent: 12.5 km, a 12.17% average, and 35.18% at its worst, climbing from 1921 m to 3442 m for a net gain of 1521 m. Pace to your FTP, gear low, and respect the altitude.

Length: 12.5 km
Average gradient: 12.17%
Max gradient: 35.18%
Start: 1921 m
Summit: 3442 m
Net gain: 1521 m
Total ascent: 1589 m
Category: HC