Puerto de Serranillos

Overview

Puerto de Serranillos is a Category 1 climb in Spain (ES), running 15.2 km from a start elevation of 646 m to a summit at 1,584 m. On paper that gives a net elevation gain of 938 m at an average gradient of 6.17% — a long, sustained ascent that sits firmly in endurance territory rather than a short, explosive effort.

The number that reframes the climb is total ascent: 1,516 m against a net gain of 938 m. That 578 m difference is climbing you do and then give back on descents and dips before the road rises again. The profile is not a clean ramp; it undulates. Practically, that means you will pay for more vertical metres than the net figure suggests, and the recovery sections come with their own tax when the road kicks back up.

How the Gradient Unfolds

A 6.17% average is a poor guide to what your legs will feel here. Averages fold the flat and downhill sections into the total, masking the pitches that actually hurt. On a climb with this much undulation, the steep ramps are steeper than the headline number, and the easier stretches are genuinely easy — the road is rarely at exactly 6%.

• Flatter and recovery sections where the gradient eases or briefly drops, letting you reset
• Repeated short climbs stacked through the profile, each demanding a fresh surge of effort
• A punishing steepest ramp reaching 23.57% — a wall that will force you out of the saddle if you are geared or paced wrong

Pacing Notes

The undulation makes even-speed pacing a trap. Chasing a constant km-per-hour forces huge power spikes on the steep ramps and wasted coasting on the descents. Instead, pace to a target sustainable power output and hold it through the rises, accepting that your speed will swing. On the shallow and downhill sections, keep the pressure on rather than freewheeling — that is where an even-effort rider gains time.

Before the ride, know your ceiling. Use the FTP estimator to set a realistic target, then ride the steep pitches just under it so the 23.57% wall does not blow your legs for the metres that follow.

Gearing

The steepest gradient governs your setup, and 23.57% demands respect. Run a compact (34-tooth inner) or sub-compact chainset paired with a wide-range cassette — a 34×32 or 34×34 low gear gives you the spin to survive the wall without grinding to a halt. Check your chainset and cassette before you leave; discovering you are over-geared halfway up a 23% ramp is not a mistake you can fix on the road.

Summary

• Length: 15.2 km
• Average gradient: 6.17%
• Maximum gradient: 23.57%
• Net elevation gain: 938 m
• Total ascent: 1,516 m
• Category: 1

Puerto de Serranillos rewards riders who read the profile rather than the average. Gear low, pace to power, and treat the extra 578 m of hidden climbing as the real challenge.