Coll de Gossem

Overview

Coll de Gossem is a long, gently graded category 3 climb that trades savage steepness for sheer duration. Over 16.5 km the road lifts you from a start elevation of 270 m to a 781 m summit, delivering 511 m of net elevation gain at an average gradient of just 3.1%. The total ascent recorded along the way is 493 m, a hint that the profile is not a single unbroken rise but a road that occasionally levels or dips before climbing again. This is a rhythm climb: the kind of ascent where the challenge is holding a steady effort for the better part of an hour rather than surviving a wall.

How the Gradient Unfolds

With a 3.1% average spread across 16.5 km, most of Gossem sits in shallow, big-ring-friendly territory. But the max gradient of 8.45% tells you the road is not uniform. Expect long stretches noticeably gentler than the average, punctuated by a handful of steeper ramps that bite toward 8.45%. Because the net gain (511 m) exceeds the total ascent figure (493 m) reported for the recorded track, the climb reads as consistently upward with only minor relief — there is little in the way of genuine descent to recover on. Treat the shallow sections as your chance to build speed and the pitches near 8.45% as brief, manageable interruptions.

Pacing Notes

On a climb this long and this shallow, pacing is everything. Because the gradient rarely forces your hand, it is easy to ride the early kilometres too hard and pay for it later. Anchor your effort to your FTP and aim to sit just below threshold across the full 16.5 km, letting the steeper ramps toward 8.45% push you briefly above without redlining. If you do not know your threshold, run the numbers through the FTP estimator before you plan a target power or heart-rate band. The goal is a metronomic effort from 270 m all the way to 781 m — steady, repeatable, and unbroken.

Gearing

The modest 3.1% average means most riders will spin comfortably in the middle of the cassette, but the 8.45% pitches and the sheer length of the effort still reward a forgiving low gear. A compact 34-tooth chainring paired with a wide-range cassette is ideal. A 34×32 will cover the majority of Gossem and keep your cadence high on the steeper ramps. If you prefer to preserve your legs across all 16.5 km, or you are carrying fatigue, drop to a 34×34 — the extra rescue gear costs nothing on the flatter stretches and keeps the harder pitches sustainable.

Summary

Coll de Gossem is an endurance climb dressed as an easy one: long, shallow, and relentless, with just enough gradient near 8.45% to keep you honest. Pace it to your threshold, gear for comfort, and enjoy 16.5 km of steady climbing to the 781 m summit.

Length: 16.5 km
Average gradient: 3.1%
Max gradient: 8.45%
Start: 270 m
Summit: 781 m
Net gain: 511 m
Total ascent: 493 m
Category: 3