Col des Brosses cycling climb profile
Col des Brosses is a long, controlled climb rather than a pure leg-breaker. The headline number is 19 km at 3.08%, starting at 389 m and topping out at 975 m. That gives it a net elevation gain of 586 m, with 616 m of total ascent.
Those figures matter because they describe a climb that rewards discipline more than aggression. The average gradient is modest, but the maximum gradient of 9.2% means the road is not simply a smooth, even drag from bottom to summit. The gap between net gain and total ascent also points to variation in the profile. In practical terms, expect a climb where the effort can feel deceptively easy at times, then suddenly require real torque when the pitch lifts.
How the gradient unfolds
From the bottom, the main feature is duration. A 19 km climb gives you enough time to make pacing mistakes, even when the average gradient sits just above 3%. The danger is not that the climb is consistently steep. It is that the easier sections can invite you to ride above sustainable pressure, leaving you short when the sharper ramps arrive.
The 9.2% maximum gradient changes how you should read the climb. On paper, Col des Brosses looks like a rolling aerobic ascent. On the bike, any ramp near that maximum will feel much harder than the average suggests, especially if you have been treating the earlier kilometres like free speed. The correct mindset is to ride the whole climb as a variable-gradient effort, not as a steady tempo road.
The summit at 975 m comes after a meaningful but not extreme vertical gain. That makes the climb a good test of pacing economy. The riders who go best here will keep the pressure smooth on the lower-gradient sections, stay seated where possible, and avoid surging every time the road kicks up.
Pacing and gearing notes
Use the first part of the climb to settle into an aerobic rhythm below threshold. If you know your /glossary/ftp, this is the type of ascent where riding slightly under that ceiling early can save the ride later. The average gradient may tempt a bigger gear, but that can become costly once the road tilts toward the 9.2% maximum.
Gearing should be chosen for the steepest ramps, not the average. You do not need to over-gear a climb like this to go fast. A setup that lets you keep cadence under control when the gradient bites will usually beat one that forces repeated low-cadence spikes.
For training, Col des Brosses is well suited to sustained tempo work, over-under efforts, or controlled threshold pacing. If you are estimating target power before the ride, use /tools/ftp-estimator as a reference, then ride the climb with restraint until the final section is clearly within reach.