Portezuelo del Cajón

Overview

Portezuelo del Cajón is a hors catégorie ascent that pairs brutal length with the added burden of altitude. Over 17.4 km the road climbs from 3184 m to a summit of 4482 m, a net gain of 1298 m at an average gradient of 7.48%. The total ascent measured along the route is 1270 m, meaning the profile is almost relentlessly upward with only the faintest respites. Even before you factor in gradient, starting at 3184 m and finishing above 4482 m puts this climb in rare company — the thin air alone reshapes how hard 7.48% feels.

How the Gradient Unfolds

The headline number is the 7.48% average, but averages hide the sting. With a maximum pitch of 11.7%, there are ramps here that bite well above the mean. The gap between the 1298 m net gain and the 1270 m of total ascent is tiny, which tells you the climb rarely gives elevation back — there are no meaningful descents to reset your legs. Expect a climb that settles into a sustained grind and then stiffens toward 11.7% on its steepest ramps. Because the road holds you close to the average for so long, the danger is starting too hot on the shallower opening and paying for it when the pitch kicks up.

Pacing Notes

At 17.4 km and 7.48% average, this is a threshold effort measured in the tens of minutes, not seconds. Ride it as a sustained tempo-to-threshold climb: settle just below your FTP on the steady sections and reserve headroom for the 11.7% ramps rather than blowing your matches early. Critically, altitude gates your power — climbing from 3184 m to 4482 m means available oxygen drops sharply, so the wattage that feels sustainable at sea level will overcook you here. Dial your target back and let the numbers guide you. If you don't know your threshold, use the FTP estimator to set a realistic ceiling before you commit to the full 17.4 km.

Gearing

Length plus altitude plus an 11.7% maximum makes gearing a first-order decision. A compact 34-tooth inner chainring is the baseline. Paired with a 34×32, most fit riders can hold cadence on the 7.48% average, but the 11.7% ramps at over 4000 m will punish anything too tall. If you have any doubt about your climbing legs or the thin air, go straight to a 34×34 — the extra tooth buys precious cadence when oxygen is scarce and the road refuses to ease. Between 34×32 and 34×34, err generous; spinning a slightly easier gear costs almost nothing and saves your legs across 17.4 km.

Summary

Portezuelo del Cajón is a true HC test: long, steep, and set at altitudes that amplify every watt of effort. Respect the 7.48% average, save something for the 11.7% pitches, gear low, and pace to the thin air.

Length: 17.4 km
Average gradient: 7.48%
Max gradient: 11.7%
Start: 3184 m
Summit: 4482 m
Net gain: 1298 m
Total ascent: 1270 m
Category: HC