Collado del Boi

Overview

Collado del Boi is a category 2 climb that trades knockout steepness for honest length. Over 11.1 km it lifts you from 418 m to a 1056 m summit, a net gain of 638 m at an average gradient of 5.77%. That average sits squarely in the range where a climb is long enough to hurt but rarely steep enough to force you off the saddle — the difficulty is measured in minutes, not in single vicious ramps. With a max gradient of 9.21%, the hardest pitches are firm rather than brutal, so the challenge is holding a steady effort while the road keeps ticking upward for the better part of eleven kilometres.

How the Gradient Unfolds

The headline number, 5.77%, describes the whole climb but not any single moment of it. Notice that the net elevation gain (638 m) runs slightly ahead of the total ascent figure of 611 m — a reminder that the recorded profile is close to relentlessly uphill, with only minor flatter breaks rather than genuine descending. The gap between the 5.77% average and the 9.21% maximum tells you where the effort lives: expect long stretches close to the mean punctuated by steeper pitches that pull well above it. When the gradient bites toward that 9.21% ceiling, it does so in bursts, then eases back to a rhythm you can settle into. Treat the average as your baseline and the steep sections as tax you pay and recover from.

Pacing Notes

On a climb of this shape, discipline beats aggression. Anchor your effort to your FTP and hold a sustainable power target rather than chasing the steep ramps. Because the climb runs long, going a few percent too hard early on the lower slopes will cost you far more than it saves near the 1056 m summit. If you are unsure of your current numbers, run them through the FTP estimator before you plan a target, then aim to ride the 5.77% sections just under threshold and absorb the surges toward 9.21% without redlining. Let your effort stay smooth even as the gradient does not.

Gearing

With 638 m to climb at a gentle-to-moderate grade, most riders will be comfortable on standard climbing gearing. A compact chainset paired with a wide cassette is the sensible default: a 34×32 low gear will spin the majority of the 5.77% sections at a healthy cadence, and it gives you enough range to sit and turn the pedals through the steeper pitches. If you prefer to protect your knees on the ramps that push toward 9.21%, or you are carrying fatigue late in a ride, a 34×34 buys you a little extra headroom for the same effort. Either choice keeps you seated and rhythmic, which is exactly how this climb rewards you.

Summary

Collado del Boi is a long, fair category 2 test — 11.1 km of steady uphill work with just enough steep punctuation to keep you honest. Pace it to your threshold, gear it to spin, and the 638 m of gain arrives without drama.

Length: 11.1 km
Average gradient: 5.77%
Max gradient: 9.21%
Start: 418 m
Summit: 1056 m
Net gain: 638 m
Total ascent: 611 m
Category: 2