Colle del Besso

Overview

Colle del Besso is an HC climb, the hardest category on the scale before you run out of numbers. It measures 13.4 km at a 7.78% average gradient, lifting you from a start elevation of 419 m to a summit at 1460 m. That works out to 1041 m of net elevation gain, with 1028 m of total ascent — the two figures sitting close together, which tells you this is an honest climb that rarely gives anything back. There is no soft-pedalling here: at HC length and gradient, the mountain simply keeps rising, and the 21.04% maximum pitch confirms it hides real teeth.

How the Gradient Unfolds

The headline 7.78% average is the number you feel in your legs for most of an hour, but averages flatten the story. With a maximum of 21.04%, the difference between the mean and the peak is over 13 percentage points — proof the climb is not uniform. Expect ramps that spike well above the average and short reprieves that pull it back down. Because net gain (1041 m) almost exactly matches total ascent (1028 m), there are essentially no descents to recover on; every metre you climb, you keep. Treat the 21.04% sections as isolated efforts rather than the norm, and settle into the sustained 7-to-8% grind that defines the bulk of the 13.4 km.

Pacing Notes

On a climb this long, discipline beats bravado. Aim to hold a steady effort just under your threshold for the sustained sections, and only spend matches on the 21.04% ramps where you have no choice. Your FTP is the single most useful number here: knowing the watts you can hold for the roughly hour-long duration of 13.4 km at 7.78% lets you ration effort instead of blowing up early. If you are unsure of that figure, run the numbers through the FTP estimator before your attempt. Start conservatively in the lower third, keep something for the steepest pitches, and let a negative split reward your patience.

Gearing

Gear for the maximum, not the average. A 21.04% wall late in a 13.4 km effort will punish anything too tall, so give yourself the range to spin rather than grind. A compact 34-tooth chainring paired with a 34×32 cassette is a sensible baseline for strong climbers, but for most riders — and for anyone likely to arrive at the steep ramps already fatigued — a 34×34 is the smarter, more forgiving choice. The extra sprocket keeps your cadence up and your knees intact when the road tilts toward 21.04%, and on an HC climb of 1041 m of gain, protecting your legs early pays dividends at the top.

Summary

Colle del Besso earns its HC rating honestly: long, relentless, and steep where it counts. At 13.4 km and 7.78% average, with a 21.04% maximum and over 1000 m of climbing, it rewards riders who pace with their head and gear with humility. Come with a plan, spin the steep bits, and the summit at 1460 m is yours.

Length: 13.4 km
Average gradient: 7.78%
Max gradient: 21.04%
Start: 419 m
Summit: 1460 m
Net gain: 1041 m
Total ascent: 1028 m
Category: HC