Alto del Oso

Overview

Alto del Oso is a category 1 climb that asks a real question of your legs: 16 km of continuous uphill, rising from 715 m at the base to a summit of 1626 m. That is 911 m of net elevation gain, with 892 m of total ascent — a sign that this is a road that climbs and keeps climbing, with almost none of the false-flat recovery you get on lesser ascents. The average gradient sits at 5.69%, a number that reads as moderate but hides real teeth: the steepest ramp touches 10.81%. On paper this is a long tempo effort; in the legs it is a sustained hour-plus grind where consistency beats bravado.

How the Gradient Unfolds

The headline number, 5.69% over 16 km, describes a climb with a genuinely serious middle rather than a token drag. With a maximum of 10.81%, the hardest pitch is nearly double the average, so expect the road to breathe: stretches close to the mean punctuated by steeper walls that spike toward that 10.81% figure. The gap between the 911 m net gain and the 892 m of measured ascent is small, telling you there is very little downhill or flat to break the rhythm — what goes up mostly stays up. Practically, that means the climb rewards riders who can hold a steady output while shifting body weight and cadence through the pitches, rather than those who surge and stall.

Pacing Notes

For a climb this long, pacing is everything. Anchor your effort to your FTP and hold a percentage of it you can sustain for the full 16 km — this is not a punchy 3 km effort where you can afford to go into the red early. The steeper ramps toward 10.81% are where riders bleed watts by over-reacting; instead, let cadence drop slightly and keep power steady across them. If you do not know your threshold, run the numbers first with the FTP estimator so you are pacing to data, not feel. Aim to arrive at the base of the steepest section with something left, because the 911 m of climbing is a slow accumulation of fatigue that punishes anyone who spends their matches in the first few kilometres.

Gearing

Given the 16 km length and pitches to 10.81%, gear conservatively — spinning saves your legs over this duration. A compact 34-tooth front with a wide cassette is the sensible baseline. A 34×32 is enough for many trained riders to stay on top of the 5.69% average and survive the ramps, but if you tire on long efforts or ride at endurance level, a 34×34 buys you crucial cadence on the steepest 10.81% sections. Err toward the easier ratio: on a climb gaining 911 m, the ability to keep the pedals turning matters far more than a slightly higher top gear you will never use.

Summary

Alto del Oso is a classic long category 1 climb — steady enough to pace, steep enough to hurt. Respect the 16 km, gear for the 10.81% ramps, and meter your effort against the full 911 m of climbing.

Length: 16 km
Average gradient: 5.69%
Max gradient: 10.81%
Start: 715 m
Summit: 1626 m
Net gain: 911 m
Total ascent: 892 m
Category: 1