Coll de Boix

Overview

Coll de Boix is a category-1 climb that asks a genuine question of your legs. Over 13.9 km it averages 6.64%, lifting you from a start elevation of 447 m to a summit at 1369 m. That is 922 m of net elevation gain, with the recorded total ascent sitting at 912 m — a sign that this is a road that mostly points relentlessly upward rather than rolling. There are no easy category-1 climbs, and Boix earns its billing through length as much as steepness: nearly fourteen kilometres of sustained work with a maximum gradient of 17.27% lurking to catch anyone who has spent their matches too early.

How the Gradient Unfolds

Read the numbers and a shape emerges. An average of 6.64% across 13.9 km means the climb never really relents, but a max of 17.27% tells you the effort is not evenly distributed. Expect long stretches that hover close to the average — the kind of gradient you can settle into — punctuated by ramps that spike well into double digits. The gap between the 6.64% average and that 17.27% peak is where the climb bites: more than ten percentage points of swing means your power will surge and ease repeatedly. Treat the summit at 1369 m as the finish line and everything below it as a rhythm exercise interrupted by hard, deliberate accelerations.

Pacing Notes

On a climb this long, pacing is everything. The steady 6.64% average makes Boix an ideal test of sustained threshold effort, so anchor your ride to your FTP rather than chasing the steep ramps. Aim to hold a controlled percentage of threshold on the consistent sections and accept short surges above it on the 17.27% pitches — then settle straight back down. Nearly 14 km at effort will punish anyone who starts too hot in the opening kilometres. If you are unsure of your current number, run the FTP estimator before you commit to a target, then ride to that ceiling with discipline all the way to 1369 m.

Gearing

With 922 m of climbing packed into 13.9 km and pitches touching 17.27%, gearing is not the place to be brave. A compact 34-tooth inner chainring paired with a wide cassette is the sensible baseline. A 34×32 will get most fit riders up the sustained 6.64% stretches at a workable cadence, but the steepest ramps are where legs blow up — so if your cassette allows it, a 34×34 buys you a crucial extra escape gear for those 17.27% moments. Choose the easier ratio if you are climbing at endurance pace or carrying fatigue; spinning a low gear beats grinding to a halt on a wall.

Summary

Coll de Boix is a long, honest category-1 test: steady enough to reward smart pacing, steep enough in places to break a poorly judged effort. Anchor to threshold, gear low, and respect the length.

Length: 13.9 km
Average gradient: 6.64%
Max gradient: 17.27%
Start: 447 m
Summit: 1369 m
Net gain: 922 m
Total ascent: 912 m
Category: 1