Puerto de Gereñu

Overview

Puerto de Gereñu is a 5.6 km category 3 climb that lifts you from 605 m at its base to 873 m at the summit. On paper that is a net gain of 268 m over an average gradient of 4.77% — the kind of number that reads as steady rather than savage. But the total ascent of 253 m tells you the road is not perfectly monotonic: there are brief flatter breaths that let the profile relax before it resumes its work. This is a climb you can ride at tempo from bottom to top, provided you respect the one section that bites hard.

How the Gradient Unfolds

The defining feature of Puerto de Gereñu is the gap between its average of 4.77% and its maximum of 12.09%. That spread of more than 7 percentage points means the difficulty is not evenly spread. Most of the 5.6 km sits comfortably below the average — long ramps in the 3–5% range where you can hold a rhythm and even carry speed. The 12.09% pitch is the exception, a short, sharp wall that spikes the effort and demands you shift down before it arrives. Because the net gain (268 m) exceeds the total ascent (253 m) figure only slightly, you know the descents and false flats are minimal; almost every metre gained is a metre you keep. Read the climb as a long, honest grind with one genuine kicker.

Pacing Notes

Because the climb is short at 5.6 km, you can afford to ride slightly above your all-day pace without blowing up. Aim to sit just under your FTP on the shallow sections, then accept a surge over the 12.09% ramp — hold that power for the minute or so it lasts, then settle back. The danger on a climb like this is going too hard early on the flatter lower slopes and having nothing left when the gradient jumps. If you do not know your threshold number, use the FTP estimator to set realistic targets before you attack. With only 268 m of vertical to clear, the whole effort is over quickly, so a controlled negative split — easing in, finishing strong over the top — usually nets the best time.

Gearing

For a climb averaging 4.77% you do not need extreme gearing, but the 12.09% maximum is where under-gearing hurts. A compact 34-tooth chainring paired with a 34×32 cassette gives most riders enough range to spin the steep pitch without grinding. If you carry less climbing power or want to keep cadence high over that wall, step up to a 34×34. Either setup lets you stay seated and steady through the hard section while leaving plenty of range for the tempo stretches. The goal is to reach the steep ramp with a gear in reserve, not to shift into your last cog at the base.

Summary

Puerto de Gereñu rewards a smart, rhythmic effort: hold tempo across the gentle majority, save something for the 12.09% kicker, and you will crest the 873 m summit with time to spare. It is short, honest, and just spicy enough to keep you honest.

Length: 5.6 km
Average gradient: 4.77%
Max gradient: 12.09%
Start: 605 m
Summit: 873 m
Net gain: 268 m
Total ascent: 253 m
Category: 3