Col de Porte

Col de Porte Cycling Climb Overview

Col de Porte is a Category 1 climb in the Chartreuse massif near Grenoble, France. The road rises 980 m net over 13.2 km from a start elevation of 364 m to a summit at 1,344 m. Total ascent across the full profile reaches 1,338 m, which means the road is not a clean straight ramp — expect some undulation and at least one stretch where gradient briefly relents before the road kicks back up.

The headline average gradient of 7.42% sits firmly in the demanding range. Hold that number in mind as a benchmark, but do not mistake it for a reliable tempo target: the max recorded gradient of 24.06% signals at least one section severe enough to require a completely different gear and pacing strategy than the rest of the climb.

How the Gradient Unfolds

With a 7.42% average across 13.2 km, Col de Porte delivers sustained effort rather than a quick punch. The gap between average (7.42%) and maximum (24.06%) gradient is large — over 16 percentage points — which tells you the climb is not evenly graded. At least one ramp hits more than three times the mean gradient. That ramp will either break a poorly paced rider or cost significant time if they arrive at it already deep in their reserves.

The 1,338 m total ascent versus 980 m net gain indicates the road gains and loses height along the route. The extra ~358 m of climbing embedded within the profile adds meaningful fatigue that a net-gain figure alone does not capture. Plan for more total work than the summit-to-start elevation difference suggests.

Pacing Notes

• Start conservatively. Thirteen kilometres is long enough that opening too hard will compound debt before you reach the steep sections.
• Protect power at the base. The lower slopes at a 7.42% average are manageable, but the gap to the 24.06% maximum means a severe ramp is waiting. Arrive at it with something left.
• Identify the steep ramp early. On your first ascent, watch your gradient readout or a pre-loaded elevation profile. When the road approaches double-digit gradients, reduce pace; at 20%+ you are in damage-limitation territory.
• Use the undulations. Where the road flattens or briefly descends, resist the urge to accelerate. These are recovery windows, not time-trial sectors.
• Target sustainable power. For a 13.2 km climb, most riders should aim for 90–95% of their functional threshold power. The steep ramp will naturally spike output — keeping everything else below threshold buys the headroom to survive it.

Gearing Recommendations

A 24.06% maximum gradient demands a low gear. On a standard compact (50/34) chainset, a rear cassette of at least 32t is advisable; a 34t gives meaningful additional margin at the cruelest pitch. Riders on standard (53/39) gearing should seriously consider a wide-range cassette (32–34t) or expect to stand and grind at the steepest section.

For gravel or touring setups, 1x drivetrains with a 42t or larger cassette sprocket handle the 24% ramp comfortably and remove the need for a front shift under load.

Sit and spin where possible on steep gradients — standing burns significantly more energy and, on a 13.2 km climb with 980 m of gain, energy conservation across the full ascent matters more than any single punchy moment.

Summary

Col de Porte is a serious Category 1 effort: long, consistently steep on average, and punishing at its hardest point. The 13.2 km distance and 980 m of net gain place it in the same tier as other major alpine day-out climbs. Respect the total ascent figure (1,338 m), plan gearing for 24% gradients, and pace to your FTP from the first kilometre.