Col du Prion

Overview

The Col du Prion is a long, deceptively gentle climb: 15.2 km of road that carries you from a valley floor at 465 m up to a summit at 922 m. On paper that is a net gain of 457 m at an average of just 3.01%, a gradient shallow enough to look almost flat in profile. In practice, a climb of this length rewards patience far more than power. It sits in category 3 — hard enough to earn a classification, but a world away from the sustained walls of a hors catégorie ascent. This is a climb of rhythm, where the challenge is measured in minutes rather than lung-searing pitches.

How the Gradient Unfolds

Do not let the 3.01% average lull you. The maximum gradient touches 10.96%, and the gap between that number and the average tells the whole story: this road is uneven. Long shallow drags — some barely tilting upward — are punctuated by short, sharper ramps that briefly bite into double digits. With a net gain of 457 m spread over 15.2 km but a total ascent of only 443 m, there is almost no false-flat descending to recover on; nearly every metre of upward drift counts toward the climb. Expect to feel comfortable for long stretches, then suddenly find yourself out of the saddle as the road kicks toward that 10.96% peak.

Pacing Notes

A climb this long is won or lost by holding a steady, sustainable effort. Anchor your pace to your FTP and resist the temptation to attack the shallow opening kilometres — you will need that reserve when the gradient spikes. Aim to sit just below threshold on the flatter drags, then allow a controlled surge over the steeper ramps rather than blowing your effort trying to hold a fixed speed. If you are unsure of your numbers, run them through the FTP estimator before you ride so you can set realistic power or heart-rate targets for the full 15.2 km. Consistency beats heroics here.

Gearing

Because the average is modest, you can climb the Col du Prion on standard road gearing without drama. A compact chainring paired with a 34×32 lowest gear is plenty for the shallow majority of the climb and will let you spin comfortably even where the road tilts toward 10.96%. If you prefer to keep your cadence high on the steeper ramps — or you are riding this at the end of a long day — a 34×34 gives you that extra bail-out cog and keeps your knees happy over the full 15.2 km. Either setup works; the deciding factor is your own comfort at low cadence rather than the climb demanding anything exotic.

Summary

The Col du Prion is a long, rhythmic category 3 climb that rewards even pacing and punishes over-eagerness on its shallow opening. Settle in, hold your effort, and let the summit at 922 m come to you.

Length: 15.2 km
Average gradient: 3.01%
Max gradient: 10.96%
Start: 465 m
Summit: 922 m
Net gain: 457 m
Total ascent: 443 m
Category: 3