Portjoch

Overview

Portjoch is a genuine hors catégorie climb, and the numbers make no attempt to soften that verdict. Over 11.7 km the road lifts you from a start elevation of 785 m to a summit at 2043 m, a net elevation gain of 1258 m. The average gradient is a ferocious 10.77%, which is steep enough to be punishing even before you meet the pitch that spikes to 25.41%. This is not a climb you ride into by accident — it is one you plan around, fuel for, and respect from the first pedal stroke.

How the Gradient Unfolds

An average of 10.77% across 11.7 km tells you there is very little relief here. On most climbs a double-digit average is padded by a few flat recovery sections; here the road simply keeps tilting. The total ascent of 1196 m sits just below the 1258 m net gain, a small difference that confirms there is almost no downhill or false-flat to reset your legs. The defining feature is the 25.41% maximum — more than double the average — so expect at least one wall where the gradient more than doubles and cadence collapses. Everything between those ramps still hovers well into the teens, meaning the "easy" parts are merely less brutal, never truly easy.

Pacing Notes

On a climb this relentless, discipline beats bravado. With 1258 m to gain over 11.7 km, an even effort just below threshold will get you to 2043 m far faster than surging early and blowing up on the 25.41% wall. Anchor your pacing to your FTP: on the sustained sections at 10.77% you want to hold a power you can defend for the full climb, then accept that the steepest pitches will briefly push you over it — that is unavoidable, not a mistake. If you are unsure of your number, run the FTP estimator before you commit, because guessing wrong here is the difference between a strong summit and a walk. Fuel early; the effort from 785 m upward is long enough that under-fuelling shows late.

Gearing

Do not underestimate what 10.77% average with a 25.41% spike demands from your drivetrain. For most riders a compact 34-tooth chainring paired with a wide cassette is the minimum sensible setup. A 34×32 will get many trained riders up the sustained slopes, but on the 25.41% ramp it can leave you grinding at a cadence low enough to threaten balance and knees. If you have any doubt about your climbing legs, fit a 34×34 — that extra sprocket buys you the spin you will crave when the road stands up. Over 11.7 km and 1258 m of gain, easier gearing is not a weakness; it is what keeps you seated and turning.

Summary

Portjoch rewards patience, honest pacing, and a cassette with room to spare. Respect the 25.41% wall, hold your effort steady across the 10.77% average, and the summit at 2043 m is entirely achievable.

Length: 11.7 km
Average gradient: 10.77%
Max gradient: 25.41%
Start: 785 m
Summit: 2043 m
Net gain: 1258 m
Total ascent: 1196 m
Category: HC