Col de Portet

What Kind of Climb Is Col de Portet?

Col de Portet is a Hors Catégorie climb in the French Pyrenees. At 12.4 km with an average gradient of 9.29% and 1,154 m of net elevation gain, it sits firmly in the category of climbs that punish optimistic early pacing. The total ascent figure — 1,999 m — is notably higher than the net gain, which tells you the road is not a simple ramp: there are undulations and false flats that disguise the overall brutality and reset your legs just enough to make the hard pitches feel worse than they should.

The maximum gradient of 31.36% places it among the steepest ramps found on any major European climb. That number is not a sustained wall — no road averages 9.29% and hits 31% for long — but it is a genuine shock to the system when it arrives, and it will arrive before your legs are ready for it if you have misjudged the lower slopes.

How the Gradient Unfolds

Starting at 790 m elevation, the climb begins before the legs have any real temperature. The opening kilometers are not a gift: at an average of 9.29%, there is essentially no easy section to use as a warm-up.

The profile's character is relentless rather than rhythmic. Unlike climbs that alternate between hard ramps and recovery grades, Col de Portet keeps the pressure on throughout. The gap between net elevation gain (1,154 m) and total ascent (1,999 m) signals that the road loses and regains height in places, which sounds like relief but in practice means your power output fluctuates without your aerobic system ever recovering fully.

The maximum pitch of 31.36% is the climb's most dangerous trap. Hit it carrying too much fatigue from the lower slopes and you face a choice between grinding to a near-halt in your easiest gear or blowing your power ceiling and paying for it in the final kilometers.

Pacing Notes

• Start conservative. An average gradient above 9% over 12.4 km means there is no climb left to recover on if you go too hard in the first third. Target a power output you can sustain for the full duration — see the FTP estimator if you need a benchmark.
• Treat the false flats as recovery, not acceleration. The total ascent figure indicates the road fluctuates in gradient. Use any easing of gradient to bring your breathing down, not to surge.
• Reserve something for the steepest pitch. The 31.36% maximum gradient requires either a seated grind in your lowest gear or a short out-of-saddle effort. Attempting it out of the saddle after 10 km at 9%+ is high risk — know which option suits your current fitness.
• Do not judge effort by speed. Gradients at this severity make speed meaningless as a pacing signal. Use power or perceived exertion calibrated against your FTP.

Gearing Recommendations

For the steepest pitches on a climb with a 31.36% maximum, a compact chainset (50/34) paired with at least a 32-tooth or 34-tooth rear cassette is the practical minimum for most riders. Anyone planning to ride the whole 12.4 km at or near threshold should consider a 36-tooth rear sprocket standard, not a luxury. Running out of gears at 30% on kilometre 10 is a mechanical problem that turns into a physical and psychological one immediately.

Riders on mullet or wide-range setups have a clear advantage here: the ability to keep cadence above 70 rpm on the steepest pitches reduces muscular fatigue and preserves the cardiovascular headroom you need to reach the summit without stopping.

Col de Portet is not a climb that rewards boldness. It rewards honesty about your current capacity and the discipline to hold to a sustainable effort when the gradient eases enough to tempt you into going faster.