Collado de Izas

Overview

Collado de Izas is a long-haul category 1 climb that trades brute steepness for relentless duration. Across 24.8 km the road lifts you from a valley floor at 847 m to a summit of 2234 m — a net gain of 1387 m. The average gradient reads a moderate 5.59%, but that headline number is a poor description of the effort ahead. A climb this long, topping out above 2200 m, asks for patience, discipline, and a plan. The total ascent of 1365 m confirms that almost every metre is spent going up, with only trivial respite along the way.

How the Gradient Unfolds

The 5.59% average hides real variety. On a climb of 24.8 km, that mean is stitched together from gentle drags where the road barely tilts and vicious pitches where it reaches a maximum of 21.71% — steep enough to force you out of the saddle and onto your lowest gear. Expect the gradient to breathe: shallow sections let you settle into a rhythm, then a ramp arrives and the number on your head unit doubles or worse. Because net gain (1387 m) slightly exceeds total ascent (1365 m), there is essentially no descending to recover on; when the slope eases, it eases toward flat, not downhill. Ride the whole thing as one sustained climb rather than a series of separate efforts.

Pacing Notes

Duration is your real opponent here, so pacing beats power spikes. Anchor your effort to your FTP and aim to hold a steady sub-threshold percentage across the full 24.8 km — the summit at 2234 m means thinner air will quietly tax you in the final kilometres, so leave margin. If you do not know your threshold, run the numbers through the FTP estimator before you commit to a target. On the 21.71% pitches, accept that your power will surge; the goal is to keep those surges brief and return to your steady effort the moment the road relents. Fuel early and often — a climb this long punishes anyone who waits until they feel empty.

Gearing

Gear for the maximum, not the average. The 5.59% mean is comfortable on almost any setup, but the 21.71% ramps will overwhelm anything too tall late in a 24.8 km effort. A compact 34-tooth chainring is the sensible front choice. Pair it with at least a 34×32 for most riders; if you climb at lower cadence, weigh less power, or simply want insurance against those steepest pitches after 1300-plus metres of climbing, step up to a 34×34. The extra range costs nothing on the shallow stretches and buys you a spinnable gear exactly where the grade turns savage.

Summary

Collado de Izas is a test of stamina above all — a long, high category 1 climb whose gentle average masks brutal ramps. Come with low gears, a disciplined pacing plan, and enough fuel to reach the top strong.

Length: 24.8 km
Average gradient: 5.59%
Max gradient: 21.71%
Start: 847 m
Summit: 2234 m
Net gain: 1387 m
Total ascent: 1365 m
Category: 1