Passo di Mezzeno

Overview

Passo di Mezzeno is an hors catégorie climb that offers nowhere to hide. Over 17.3 km the road averages 9.73%, a number that puts it among the most sustained hard climbs you can attempt. You start at 455 m and finish at 2133 m, a net gain of 1678 m of altitude gained under your wheels. The total ascent of 1609 m confirms this is very close to a pure uphill effort — there is almost no descending or flat relief to break the rhythm. Add a maximum pitch of 31.52% and you have a climb that rewards patience and punishes anyone who starts too fast.

How the Gradient Unfolds

The defining feature here is consistency of difficulty rather than a single decisive wall. An average of 9.73% held across 17.3 km means the "easy" sections are still steep, and the hard sections are savage. The gap between the 9.73% average and the 31.52% maximum tells the story: expect the road to kick well into the twenties on its steepest ramps, then settle back toward — but rarely below — the average. Because the total ascent (1609 m) sits just under the net gain (1678 m), the profile trends relentlessly upward with only the faintest easing. Treat every gentler stretch as recovery, because another double-digit ramp is always waiting.

Pacing Notes

On a climb this long and steep, pacing discipline decides everything. Anchor your effort to your FTP and hold a wattage you can genuinely sustain for the better part of an hour — the 17.3 km distance guarantees a long time in the saddle. If you do not know your threshold, run the numbers through the FTP estimator before you commit. The steepest 31.52% pitches will force short surges above threshold; the key is to spike briefly, then bleed the effort back down rather than chasing a steady pace over the top. With 1678 m to climb, going into the red early on the lower slopes is the fastest way to blow up before the 2133 m summit.

Gearing

Do not under-gear this one. A sustained 9.73% average across 17.3 km, with ramps to 31.52%, demands the widest range you can fit. A compact 34-tooth chainring paired with at least a 34×32 cassette is the sensible starting point for strong climbers, and most riders will be far happier with a 34×34 for the steepest sections. If your setup allows an even larger sprocket, use it — spinning a low gear at cadence protects your legs across 1678 m of climbing far better than grinding a gear that is marginally too tall.

Summary

Passo di Mezzeno is a true HC test: long, unrelentingly steep, and topping out high. Respect the average, gear low, and pace to your threshold, and the 2133 m summit is within reach.

Length: 17.3 km
Average gradient: 9.73%
Max gradient: 31.52%
Start: 455 m
Summit: 2133 m
Net gain: 1678 m
Total ascent: 1609 m
Category: HC