Portes de Culet

Overview

Portes de Culet is a hors catégorie climb, the hardest classification on the scale that runs HC, 1, 2, 3, 4. It stretches 17.1 km and averages 8.2%, lifting you from a start elevation of 384 m to a summit at 1788 m. That is 1404 m of net elevation gain and 1383 m of total ascent — figures that mark this out as a genuine mountain effort rather than a rolling test. There is no easing into it: an 8.2% average sustained across 17.1 km means the road tips consistently upward, and the 12.09% maximum gradient tells you the steepest ramps demand real punch.

How the Gradient Unfolds

The shape of Portes de Culet is defined by consistency. With net gain (1404 m) and total ascent (1383 m) almost identical, there is virtually no descending or false flat to break the rhythm — nearly every metre you climb, you keep. Over 17.1 km at 8.2%, the climb never truly relents, and the gap between the 8.2% average and the 12.09% maximum shows that the hardest sections rise roughly 3.89 percentage points above the norm. Expect the gradient to hover near average for long stretches, then bite harder on the steepest ramps toward that 12.09% ceiling. This is a climb where pacing discipline matters more than explosive attacks.

Pacing Notes

On a climb this long and this steep, your FTP is the number that governs whether you reach the 1788 m summit in control or in trouble. At 17.1 km and 8.2%, most riders will be on the road for well over an hour, so target an intensity you can hold for the full duration rather than the first few kilometres. Ride the opening third slightly under threshold, bank the rhythm, and save a small reserve for the 12.09% pitches. If you are unsure of your threshold, run the numbers through the FTP estimator before you commit — going out too hard on 1404 m of climbing is punishing to recover from.

Gearing

An 8.2% average over 17.1 km with ramps to 12.09% is exactly the profile that rewards low gearing. A compact 34-tooth inner chainring is the sensible starting point. Pair it with a 34×32 as a minimum for riders with strong legs and a steady cadence, but for most, a 34×34 is the smarter choice — that extra sprocket keeps your cadence spinning on the steepest sections rather than grinding, which protects your legs across a climb that gains 1404 m. If your bike accepts it, err toward the 34×34; you rarely regret having one more gear on an HC ascent.

Summary

Portes de Culet is a true HC climb that asks for patience, low gearing, and a well-judged effort. Its near-perfect consistency — 1404 m of net gain against 1383 m of total ascent — means the reward comes not from surviving a single ramp but from holding your rhythm across all 17.1 km to the 1788 m summit.

Length: 17.1 km
Average gradient: 8.2%
Max gradient: 12.09%
Start: 384 m
Summit: 1788 m
Net gain: 1404 m
Total ascent: 1383 m
Category: HC