Pas de la Bosse

Overview

Pas de la Bosse is a category 1 climb that stretches for 17.1 km, a length that puts it firmly among the long-haul efforts where patience matters as much as power. It begins at 795 m and tops out at 1813 m, delivering a net elevation gain of 1018 m over the ascent. The average gradient sits at 5.97%, a figure that reads as moderate on paper but rarely feels that way in the legs once you are deep into the climb. With a total ascent of 979 m recorded across its rolling profile, this is a climb that rewards riders who can settle into a rhythm and hold it.

How the Gradient Unfolds

The headline average of 5.97% hides a lot of variation. A max gradient of 31.72% tells you this climb has at least one savage pitch that will spike your heart rate and force you out of the saddle. Ramps like that are wildly steeper than the average, which means the road must also ease off in places to keep the overall figure where it is. Expect the profile to breathe: stretches near or below the 5.97% mean where you can recover, punctuated by sharp kicks that undo any complacency. The gap between the 979 m of total ascent and the 1018 m of net gain is small, so this is a climb that mostly points relentlessly upward rather than giving back much descending along the way.

Pacing Notes

On a 17.1 km climb, going out too hard is the classic error. Anchor your effort to your sustainable threshold rather than the feel of the early slopes. Riders who know their FTP can hold a steady percentage of it across the full length and avoid blowing up on the steep ramps. If you have not tested recently, the FTP estimator will give you a working number to pace against. Treat the 31.72% pitch as a moment to survive, not a place to attack — spin what you can, keep the effort controlled, and resume your rhythm once the road relents. With 1018 m of net gain ahead, discipline in the first half buys you the legs to finish strong.

Gearing

Given the sustained 5.97% average and that brutal 31.72% maximum, gear conservatively. A compact chainset with a wide-range cassette is the sensible baseline here. A 34×32 will get most fit riders up the steady sections without grinding, but the steepest ramp really argues for a 34×34, which gives you the extra spinning room to keep cadence up when the gradient bites. On a climb this long, protecting your knees and holding a smooth cadence over the full 17.1 km matters more than saving a few grams — err toward the easier ratio.

Summary

Pas de la Bosse is a long, category 1 test that demands respect for its length and its single vicious pitch. Pace it patiently, gear it generously, and the 1018 m of vertical will come.

Length: 17.1 km
Average gradient: 5.97%
Max gradient: 31.72%
Start: 795 m
Summit: 1813 m
Net gain: 1018 m
Total ascent: 979 m
Category: 1