Col de la Charbonnière

Overview

Col de la Charbonnière earns its Category 1 rating honestly. The climb runs 10.6 km from a start elevation of 264 m to a summit at 968 m, accumulating 1,039 m of total ascent — slightly more than the raw elevation difference suggests, which means the road is not entirely kind on the way up. An average gradient of 6.67% is respectable but manageable; the 20.24% maximum gradient is the number that will define your day if you approach it without a plan.

How the Gradient Unfolds

At 6.67% average over 10.6 km, you are looking at sustained, honest climbing — not a false-flat slog, but not wall-to-wall suffering either. The gap between that average and the 20.24% maximum tells you everything: somewhere on this road there is a ramp that roughly triples the mean gradient. That kind of spike does not appear without warning in the terrain, but it can appear without warning in your legs if your opening kilometres are ridden too aggressively.

What to Expect in Phases

• Early kilometres: The start elevation of 264 m puts you in valley terrain. Expect the road to build progressively rather than bite immediately. Use this section to settle into a controlled effort — well below threshold if the maximum ramp is still ahead.
• Mid-climb: With 1,039 m of total ascent packed into 10.6 km, there is no extended flat relief. Gradient likely oscillates rather than holds perfectly steady, so monitor perceived effort rather than a fixed speed target.
• The steep ramp: At 20.24%, this section demands a gear you can actually turn. If you arrive here already deep in your FTP red zone, you will either stall or blow up before the summit at 968 m.

Pacing Notes

The single most common mistake on a climb with a wide gradient range is riding the average. On Col de la Charbonnière, 6.67% average disguises that peak of over 20%. Treat the climb in two modes:

1. Below the ramp: ride at a sustainable power — roughly 90–95% of FTP for trained climbers, less if you have not done a recent test (use the FTP estimator to confirm your current baseline).
2. On the steep section: shift down early, before cadence drops below 70 rpm. Grinding a big gear at 20% burns matches you cannot relight.

Heart rate will lag on short steep sections, so do not use HR alone to judge effort on the ramp. Power or cadence control is more reliable here.

Gearing Recommendations

With a maximum gradient of 20.24%, a compact or semi-compact chainset paired with an 11-32 or wider cassette is appropriate for most riders. On a standard 53/39 with an 11-28, the steepest section becomes a leg-strength problem rather than a pacing problem — survivable for strong riders, a walk risk for anyone who has already spent significant energy on the lower slopes.

If you are climbing Col de la Charbonnière as part of a longer day, gear conservatively. There is no shame in having a gear left at 20%.

Summary

Col de la Charbonnière is a complete Category 1 climb — long enough to accumulate serious fatigue, steep enough in its hardest section to crack a rider who has not paced the approach correctly. Respect the maximum gradient, arrive at it with fuel in the tank, and the summit is manageable.