Portes de l'Hiver

Overview

Portes de l'Hiver is an hors catégorie (HC) monster, the hardest tier a climb can carry. It runs for 27.4 km, lifting you from a valley floor at 412 m to a summit at 2184 m. That is a net elevation gain of 1772 m, but the road does not climb in a clean line — the total ascent of 1952 m tells you there are dips and recoveries folded in, roughly 180 m of climbing you effectively do twice. The headline average of 6.47% sounds humane. The 27.9% max gradient tells the truer story: this climb has teeth, and it bites when you least expect it.

How the Gradient Unfolds

Averages flatten drama, and 6.47% over 27.4 km hides a lot. The gap between the 1952 m of total ascent and the 1772 m of net gain means the profile is not monotonic — expect false flats and short descents that interrupt any rhythm you build. Those breaks are a gift and a trap: they let you breathe, but they also break your cadence and cool your legs before the next wall. And the walls are real. A 27.9% pitch is well over four times the average, the kind of ramp where the road tilts up like a drawbridge and your front wheel feels light. Treat the early kilometres as deceptively steady and save something for the sections where the gradient spikes far above that 6.47% mean.

Pacing Notes

On a climb this long, pacing is everything. Twenty-seven-plus kilometres at threshold is not a realistic ask for most riders, so anchor your effort to your FTP and ride the lower slopes a touch under it, banking energy for the steep pitches. If you do not know your number, get a working estimate first with the FTP estimator — guessing high here is how you blow up before the summit. The smartest approach is to hold steady power through the false flats rather than chasing them, then accept that the 27.9% ramps will briefly push you into the red no matter how disciplined you are. Absorb those spikes, settle back down, and let the 1772 m of gain come to you one climb at a time.

Gearing

Gear for the worst pitch, not the average. With a 27.9% max and 27.4 km in your legs before you even reach the hardest ramps, you want the widest range you can run. A compact 34-tooth chainring paired with a 34×32 cassette is a sensible floor for strong climbers; anything less and the steep sections force you out of the saddle to grind. If you have the derailleur capacity, go to 34×34 — that extra cog buys you cadence and spares your knees over 1952 m of total ascent. Nobody has ever regretted an easier gear at 2184 m.

Summary

Portes de l'Hiver earns its HC rating: long, uneven, and capped by pitches steep enough to stop you dead. Respect the distance, gear low, and pace off your threshold from the bottom.

Length: 27.4 km
Average gradient: 6.47%
Max gradient: 27.9%
Start: 412 m
Summit: 2184 m
Net gain: 1772 m
Total ascent: 1952 m
Category: HC