Collet del Bas

Overview

Collet del Bas is a category 1 ascent that asks for patience and honest legs. Over 13.6 km it climbs from 468 m at the base to a summit of 1370 m, a net gain of 902 m and a total ascent of 903 m once the small dips along the way are counted. The average gradient of 6.64% places it firmly in the "sustained tempo" bracket — not a wall, but never a rest either. With a maximum pitch of 16.21%, the climb has enough sharp punctuation to hurt anyone who arrives at the base already frayed. This is a climb where the summit is earned kilometre by kilometre rather than survived in one heroic effort.

How the Gradient Unfolds

The defining number here is the gap between the 6.64% average and the 16.21% maximum. That spread of nearly ten points tells you the road is not evenly graded: long stretches sit close to the average, while isolated ramps spike well above it. Spread across 13.6 km, the 902 m of net elevation means you are, on average, gaining roughly one metre of height for every fifteen you ride forward. Expect the profile to breathe — sections that let you settle into a rhythm, then a steepening that forces a gear change and a moment of concentration before the grade relents again. Reading the road ahead matters more here than raw power.

Pacing Notes

Treat Collet del Bas as an effort held just under threshold. On a climb this long, the temptation is to chase the early ramps; resist it. Anchor your pacing to your FTP and aim to sit a touch below it on the sustained 6.64% sections, keeping enough in reserve to absorb the pitches that climb toward 16.21% without blowing apart. If you do not know your current numbers, run them through the FTP estimator before you plan the day. The steep ramps are where most riders overspend — let your power drift slightly over threshold on those, then bring it back down the moment the road eases. Over 13.6 km, discipline in the first two-thirds is what leaves you with legs for the summit.

Gearing

Gearing should be chosen for the 16.21% maximum, not the 6.64% average — the ramps decide your comfort. For most riders a compact chainset paired with a wide-range cassette is the sensible baseline. A 34×32 will get strong climbers up the sustained sections while keeping cadence respectable, but on a climb of this length the extra range of a 34×34 buys real insurance for the steepest pitches late on, when fatigue has already accumulated. If you tend to grind rather than spin, or you are carrying loaded bags, size up rather than regret it half way. The goal is to keep your legs turning over the whole 13.6 km, not to muscle through in a gear that is a size too tall.

Summary

Collet del Bas rewards the rider who paces honestly, gears generously, and respects the difference between its steady average and its sharp maximum. Come in fresh, hold something back, and the 902 m of climbing arrives more smoothly than the numbers suggest.

Length: 13.6 km
Average gradient: 6.64%
Max gradient: 16.21%
Start: 468 m
Summit: 1370 m
Net gain: 902 m
Total ascent: 903 m
Category: 1