Alto de los Valles

Overview

Alto de los Valles is a genuine hors catégorie (HC) test — the hardest rung on the cycling difficulty ladder, sitting above categories 1 through 4. It runs 21.6 km from a valley floor at 1097 m all the way up to a summit at 2505 m, a net gain of 1408 m. The average gradient of 6.53% sounds civil on paper, but at this length and with a summit above 2500 m, thinning air compounds every pedal stroke. This is a climb measured in patience as much as power.

How the Gradient Unfolds

The headline number is 6.53% averaged across all 21.6 km, but averages hide the story. The total ascent of 1389 m against a net gain of 1408 m tells you the road climbs almost relentlessly — there is very little descending or false-flat recovery folded into the profile. What breaks the rhythm are the ramps. The gradient spikes as high as 17.01%, more than two and a half times the average, so stretches that sit well above the mean are inevitable. Expect the climb to alternate between sustained mid-single-digit grinding and sharp kicks that force you out of the saddle. Because the ascent is so consistent, you rarely get a flat section to shake out your legs before the next steep pitch arrives.

Pacing Notes

On a climb this long, discipline beats bravado. Anchor your effort to your FTP and treat the early kilometres as a governor, not a stage to attack. A useful rule for HC efforts is to hold slightly below threshold on the average grades so you have headroom for the 17.01% ramps, which will briefly spike your power far above target whether you like it or not. Riders who go out hard in the first few kilometres almost always pay for it in the final third, where the summit's altitude above 2505 m saps whatever reserves remain. If you are unsure of your threshold, run the numbers through the FTP estimator before you plan your pacing so your zones reflect reality rather than optimism.

Gearing

Do not underestimate the gearing you need here. With a 17.01% max gradient stacked on top of 21.6 km of climbing, you want a generous bailout cog. A compact 34-tooth chainring paired with a 34×32 cassette is a sensible baseline for strong climbers, giving you a low gear to spin the steep ramps without cross-loading your knees. If you are a lighter power rider, carrying luggage, or simply value cadence over grinding, size up to a 34×34. That extra tooth makes the difference between spinning and slogging when the road tilts toward its steepest pitches near the top, where altitude has already eroded your output.

Summary

Alto de los Valles is a summit-finish HC climb that rewards even pacing, patient gearing, and respect for altitude. Get your effort right early and the 6.53% average is manageable; get greedy and the final kilometres will find you out.

Length: 21.6 km
Average gradient: 6.53%
Max gradient: 17.01%
Start: 1097 m
Summit: 2505 m
Net gain: 1408 m
Total ascent: 1389 m
Category: HC