Port de Rat

Overview

Port de Rat is a hors catégorie (HC) climb, the hardest category there is, and its scale explains why. Over 35.5 km the road lifts you from a start elevation of 481 m to a summit of 2548 m, a net elevation gain of 2067 m. The average gradient reads a deceptively civil 5.82%, but at this length the number that matters is duration, not slope. This is a climb measured in hours, not minutes, and it demands a plan.

How the Gradient Unfolds

An average of 5.82% across 35.5 km almost never means a steady 5.82% the whole way. The tell is in the two ascent figures: the net elevation gain is 2067 m, yet the total ascent is 2982 m. That 915 m gap (2982 minus 2067) is climbing you do and then give back on descents and false flats before regaining it. In practice, that means rolling or undulating sections punctuate the overall rise, and the real climbing pitches are steeper than the 5.82% average suggests. Expect the road to hand you brief recoveries, then reclaim them, all the way to 2548 m.

Pacing Notes

On a climb this long, pacing is everything. Aim to sit at or just below your sustainable threshold — think in terms of your FTP rather than how you feel in the first kilometre, because how you feel early on a 35.5 km climb is a poor guide to how you'll feel near 2548 m. If you don't know your threshold, run the numbers first with the FTP estimator so you set a target you can actually hold for the full 2067 m of gain.

The temptation on the gentler stretches is to push. Don't. Bank the easy metres at a controlled effort and save your matches for the steeper pitches hidden inside that 5.82% average. Fuel early and often — the 915 m of "extra" climbing from those undulations adds up over the hours.

Gearing

For an HC climb of this length, gear conservatively — you want low ratios in reserve for the back half. A 34×32 is a sensible baseline for strong climbers, giving you a bailout gear for the steeper ramps that lurk beneath the 5.82% average. If you're carrying luggage, riding tired, or simply want to spin rather than grind across 35.5 km, step down to a 34×34. The extra range costs you nothing on the flatter sections and protects your legs and knees over 2067 m of ascent to 2548 m.

Summary

Port de Rat is a true HC test of endurance: 35.5 km, a 5.82% average that hides steeper pitches, and 2982 m of total ascent to reach 2548 m. Pace to your threshold, gear low, and respect the distance.

Length: 35.5 km
Average gradient: 5.82%
Max gradient: n/a
Start: 481 m
Summit: 2548 m
Net gain: 2067 m
Total ascent: 2982 m
Category: HC