Alto Boquerón del Carmen

Overview

Alto Boquerón del Carmen is a genuine hors catégorie (HC) climb — the hardest classification there is, sitting above categories 1, 2, 3 and 4. It runs for 31.6 km at an average gradient of 6.07%, starting at 2002 m and finishing at 3919 m. That is a net elevation gain of 1917 m, but the total ascent is 2088 m, which tells you the road does not climb in a single clean line: there are 171 m of rolling relief hidden inside the profile. Add the thin air of a summit close to 3919 m and you have a climb that punishes both fitness and patience.

How the Gradient Unfolds

An average of 6.07% over 31.6 km sounds steady, but the gap between the net gain of 1917 m and the total ascent of 2088 m confirms the grade is uneven. Expect stretches that sit near the average, softer sections that let the road breathe, and sharp ramps that spike toward the maximum gradient of 16.12% — nearly three times the average. Those steep pitches are where the climb bites. Because the summit sits at 3919 m, every effort near the top costs more than the same effort would lower down; the gradient on paper stays the same, but your legs feel the altitude tax on the final kilometres.

Pacing Notes

On a climb this long, discipline beats bravado. Your target power should sit around your FTP — the threshold you can hold for roughly an hour — but with 31.6 km ahead, riding slightly under threshold for the bulk of the climb is smarter than chasing the average gradient early. Bank effort for the 16.12% ramps rather than the 6.07% sections; the steep pitches are where surges are unavoidable and where over-cooking it earliest will cost you most. If you are not sure where your threshold sits, run the numbers through the FTP estimator before you go, then set a ceiling and hold it. Remember the altitude: from 2002 m to 3919 m your sustainable power drops as you climb, so a pacing plan built at sea level will feel optimistic near the top.

Gearing

At 31.6 km averaging 6.07% with ramps hitting 16.12%, gearing is not a place to be brave. A compact 34-tooth front paired with a wide-range cassette is the sensible baseline. A 34×32 will get most strong riders up the steady sections, but on the 16.12% pitches — especially after 2000-plus metres of climbing and at altitude — a 34×34 gives you the extra cadence room to spin rather than grind. If your setup allows an even larger sprocket, take it. Preserving your knees and your cadence over 2088 m of total ascent matters more than saving a few grams.

Summary

Alto Boquerón del Carmen is a long, high-altitude HC test: 31.6 km of climbing, a steady-looking 6.07% average hiding 16.12% ramps, and a summit at 3919 m that makes the final metres the hardest. Pace to your threshold, gear low, and respect the thin air.

Length: 31.6 km
Average gradient: 6.07%
Max gradient: 16.12%
Start: 2002 m
Summit: 3919 m
Net gain: 1917 m
Total ascent: 2088 m
Category: HC