Collado Aratzarte

Overview

Collado Aratzarte is a long, sustained category 1 ascent that rewards patience over punch. It runs for 18.7 km, starting at 247 m and topping out at 1273 m, for a net elevation gain of 1026 m. The road climbs 5.48% on average, which sounds gentle until you factor in the length: nearly nineteen kilometres of continuous uphill effort is a serious undertaking whatever your fitness. With a total ascent of 1020 m recorded across its profile, this is a climb where the summit elevation of 1273 m has to be earned methodically, kilometre by kilometre.

How the Gradient Unfolds

Do not be lulled by the 5.48% average. That figure is the smoothed-out story of the climb, but the road is not uniform. Peak gradients reach 19.41%, almost four times the average, which tells you the ascent hides steep ramps between shallower stretches. A climb that gains 1026 m over 18.7 km but spikes to nearly 20% is one that trades easier flanks for sharp, leg-loading pitches. Expect to shift often: sections well below the average give you room to recover, then the gradient stiffens without much warning. Reading the road ahead and anticipating those ramps is the difference between a controlled climb and a blow-up.

Pacing Notes

On a climb this long, pacing is everything. The single biggest mistake is chasing the early kilometres and paying for it near the 1273 m summit. Anchor your effort to your FTP and aim to ride the sustained portions just under threshold, leaving headroom to absorb the 19.41% spikes without going deep into the red. Over 18.7 km, a small overpace compounds badly. If you are unsure of your numbers, run them through the FTP estimator before you go, then set a wattage ceiling you can hold for the full duration. Treat the steep ramps as brief surges above your target, then settle straight back to your climbing rhythm once the gradient eases.

Gearing

For a 1020 m ascent averaging 5.48% with pitches to 19.41%, gearing generously is not a luxury, it is a survival strategy. A compact 34-tooth chainring paired with a 34×32 cassette is a sensible baseline for strong climbers, giving a low enough ratio to spin the sustained sections without grinding. But given how steep the 19.41% ramps get, most riders will thank themselves for a 34×34. That extra sprocket lets you keep a fluid cadence on the worst pitches instead of muscling the pedals over, which preserves your legs across all 18.7 km. When in doubt on a climb this long and this spiky, take the easier gear.

Summary

Collado Aratzarte is a proper endurance climb: long enough to test your pacing, steep enough in places to test your gearing, and consistent enough to reward a rider who holds their rhythm from 247 m to the top. Respect the length, gear for the spikes, and it becomes one of the most satisfying category 1 efforts you can log.

Length: 18.7 km
Average gradient: 5.48%
Max gradient: 19.41%
Start: 247 m
Summit: 1273 m
Net gain: 1026 m
Total ascent: 1020 m
Category: 1