Alto del Trueno

Overview

Alto del Trueno is a category-1 climb that stretches 15.4 km from a start elevation of 963 m to a summit at 1871 m. On paper the 5.88% average gradient reads as steady and civilized, but the numbers hide the real story. Net elevation gain lands at 908 m, while total ascent measures 880 m — a small difference that tells you the road is not a single unbroken wall but a surface with brief lulls where the grade eases before climbing again. This is a long climb where patience matters as much as power.

How the Gradient Unfolds

The 5.88% average is a useful anchor, but it flattens out a road that clearly refuses to be uniform. With a max gradient of 21.41%, there is at least one pitch here that nearly quadruples the average — the kind of ramp that spikes your heart rate and forces you out of the saddle whether you planned to stand or not. Because total ascent (880 m) sits just below net gain (908 m), you can expect the climb to trend relentlessly upward with only the faintest recovery sections. Treat every kilometer as if the next corner could hide that 21.41% wall, because over 15.4 km the punishing sections will find you when your legs are least ready for them.

Pacing Notes

On a climb this long, discipline beats ambition. Anchor your effort to your FTP and resist the urge to chase the early gradient. A climb of 15.4 km at 5.88% will keep you working for a long time, so ride the lower ramps a touch below threshold and bank that reserve for the 21.41% pitch, where surging is unavoidable and expensive. If you do not know your threshold, run your recent efforts through the FTP estimator before your ride so you can set realistic power targets rather than guessing on the road. The goal is to arrive at the steepest ramp with enough headroom to survive it without blowing apart for the kilometers that remain to the 1871 m summit.

Gearing

With 908 m of climbing packed into 15.4 km and a 21.41% maximum gradient, gearing is not a luxury here — it is the difference between spinning and grinding to a stop. A compact 34-tooth chainring is the sensible front choice. Pair it with at least a 34×32 for the sustained 5.88% work, but if you have any doubt about your climbing legs, size up to 34×34 to keep cadence alive on that 21.41% ramp. The lower ratio costs you nothing on the shallow sections and buys you everything when the road stands up.

Summary

Alto del Trueno rewards riders who respect its length before its steepness. Meter out your effort across the 15.4 km, save something for the 21.41% wall, and let low gearing carry you the final stretch to 1871 m.

Length: 15.4 km
Average gradient: 5.88%
Max gradient: 21.41%
Start: 963 m
Summit: 1871 m
Net gain: 908 m
Total ascent: 880 m
Category: 1