Fenestre pass

What Kind of Climb Is Fenestre Pass?

Fenestre pass sits squarely in the Hors Catégorie bracket — the classification reserved for climbs that don't fit neatly on a difficulty scale. The numbers justify the label: 11.9 km of road, an average gradient of 8.19%, and a maximum pitch of 48.08%. That last figure is not a typo. Somewhere on this road there is a ramp steep enough to stop most riders dead if they hesitate for a second.

The start elevation of 1,476 m means you're already high before the climbing even begins. By the summit at 2,454 m, you've accumulated 1,814 m of total ascent — a figure meaningfully higher than the raw start-to-finish elevation difference, which tells you the road does not simply arrow straight upward. There are false flats, undulations, and sections that reload your legs before the next serious ramp.

How the Gradient Unfolds

With an average of 8.19% across 11.9 km, Fenestre pass is not a climb where you can bank easy kilometres at the bottom and simply survive the top. An 8%+ average sustained over nearly 12 km demands consistent output throughout.

The 48.08% maximum gradient is an extreme outlier — almost certainly a short, sharp wall rather than a prolonged section. Ramps in that range are more about bike handling and raw torque than aerobic capacity. On a road bike with standard gearing, a 48% pitch is unrideable for most athletes. On a compact or sub-compact setup with a wide-range cassette, it may be survivable if momentum is preserved entering the ramp. Lose speed before it and you'll be putting a foot down.

Practically, treat the average gradient as your ceiling for sustainable effort, not your floor. Anything approaching 8% for that duration will put you deep into threshold territory. The occasional punchy ramp will spike power well above threshold; the recoveries between those ramps are where you claw back.

Pacing Notes

• Don't start too hard. Starting elevation is already above 1,476 m. If you're not acclimatised, perceived effort will outpace actual power output from the first kilometre.
• Gear conservatively. A 34×32 minimum at the back is sensible. Given the 48% maximum, a 34×34 or a 1x drivetrain with a 10-50 cassette is worth considering if you want any chance of turning the pedals over on the worst pitches.
• Protect your legs through 50–75% of the climb. The total ascent figure of 1,814 m means the road keeps taking. Blowing up at kilometre 7 leaves over 4 km of serious gradient to negotiate on empty legs.
• Use the undulations. Wherever gradient eases, shift up slightly and spin rather than coast. Active recovery on the bike keeps blood moving without costing watts.
• Know where the maximum gradient sits. Reconnoitre via mapping tools or ride reports before your attempt. Arriving at a 48% ramp without knowing it's there is how riders get into trouble.

Who This Climb Is For

Fenestre pass is not an introductory alpine climb. The HC category, the extended length at over 8% average, and the extreme maximum gradient make it a serious objective for experienced climbers. If you want to benchmark your readiness, use the FTP estimator to understand what sustained power you can hold over a 45–75 minute effort — that's roughly the window a strong amateur will spend on this road.

For context on how this stacks up against other French HC climbs, see the Neverchill climbs directory.