Col de Bonnecombe

What to Expect from the Col de Bonnecombe

The Col de Bonnecombe sits in France at a start elevation of 1,009 m, climbing 349 m of total ascent to a summit at 1,341 m. At 5.8 km long with a 5.71% average gradient, it falls into Category 3 — steady enough to demand respect on tired legs, short enough to be ridden aggressively if you have something to prove.

The average gradient makes this look manageable on paper, but the 16.42% maximum gradient tells a different story. Somewhere on this climb, the road kicks hard. That gap between the mean and the peak — nearly 11 percentage points — signals a profile that is not smooth or linear. Expect at least one section that bears no resemblance to the overall average.

How the Gradient Unfolds

With a 5.71% mean across 5.8 km, the bulk of this climb is in the moderate range. Riders comfortable pushing a steady threshold pace on FTP-calibrated efforts will find much of the ascent controllable. The danger is the sharp ramp hiding within that average.

The 16.42% maximum is steep enough to stall riders who arrive at it over-geared or already deep in the red. On gradients above 15%, cadence drops fast unless you have the gearing to match. A short, brutal pitch at that angle can cost 30–60 seconds and spike heart rate into a zone that takes several minutes to recover from — even if the gradient relents immediately after.

Pacing Approach

• Start conservatively. The start elevation of 1,009 m is high enough that some riders will feel mild altitude effects, particularly if coming from lower ground. Don't overcook the opening kilometre.
• Target effort, not speed. On a climb with this much gradient variance, speed is a misleading metric. Ride to a power or perceived exertion target instead. If you need a baseline, use the FTP estimator before the day.
• Anticipate the steep section. If you're carrying data from a previous ride or a GPS route file, identify where the 16% pitch sits and approach it with reserve. Shift down a gear earlier than feels necessary — once the gradient hits, there's no smooth gear change to be made.
• Recovery after the ramp. If the steep pitch comes mid-climb, use any easier gradient that follows to lower your heart rate before the summit push rather than pressing immediately.

Gearing Notes

For a climb averaging 5.71% over 5.8 km, most road setups with a compact chainset (50/34) and an 11-28 or 11-32 cassette will get riders through the sustained sections without issue. The 16.42% maximum is the constraint. On that gradient, even a 34/28 combination puts out significant torque demand. Riders who struggle on steep pitches should consider a 34/32 or a wide-range cassette if their drivetrain allows it.

The climb is short enough — 349 m of total ascent — that muscular fatigue from grinding a harder gear for one severe pitch is a real consideration, especially if Bonnecombe appears mid-route rather than as a standalone effort.

Summary

The Col de Bonnecombe is not a long sufferfest, but it is not a throwaway Category 3, either. The combination of a moderate average and a near-17% maximum demands attentiveness. Ride it even-handed, respect the spike, and there's no reason it should blow up a day's effort.