Colle di Mezzo

Overview

Colle di Mezzo is a short climb only in the sense that it ends. Over 5.4 km it averages a savage 16.33% gradient, dragging you from a start elevation of 970 m to a summit at 1844 m — a net gain of 874 m in barely five kilometres. That gradient alone earns it the HC (hors catégorie) label, the hardest rating there is, sitting above categories 1 through 4. There is nowhere on this climb to hide. Where most classified ascents mix steep pitches with recovery, Colle di Mezzo simply points uphill and stays there.

How the Gradient Unfolds

The headline number — 16.33% average — is not a fluke created by one wall dragging up a mellow road. On a climb this short, an average that high means the whole thing is relentless. The road bites hard from the base at 970 m and never truly relents across the 5.4 km to the top. The peak pitch reaches 29.46%, close to double the average, so expect the steepest ramps to feel like they are trying to stop your wheels entirely. Because total ascent is 827 m while net gain is 874 m, the road climbs almost every metre it covers — there is essentially no descending or flat respite mixed in. This is a straight, brutal upward line: 874 m gained, top to bottom, with the hardest section demanding you stay seated for traction and grind.

Pacing Notes

On a climb this steep, pacing is really damage control. The 16.33% average means power spikes well above your sustainable threshold are unavoidable, especially through the 29.46% ramp. Anchor your effort to your FTP and accept that short surges will punch far over it — the goal is to keep the overshoots brief and recover the instant the gradient eases a fraction. If you are unsure of your threshold before tackling 5.4 km of this, run the numbers first with the FTP estimator. Start conservatively: the summit sits at 1844 m and burning your matches in the first kilometre will leave nothing for the upper slopes.

Gearing

Do not under-gear this one. With a 16.33% average and pitches to 29.46%, most riders will want the easiest ratio they can bolt on. A compact 34-tooth chainring paired with a 34×32 cassette is the sensible minimum, and even then you will be turning it over slowly on the steepest ramps. If your legs or your setup allow, go further: a 34×34 gives you meaningful extra relief and keeps your cadence out of the knee-wrecking zone when the road tips toward 29.46%. On a wall this steep, a slightly easier gear you can spin beats a harder one you have to stamp on.

Summary

Colle di Mezzo is a pure test: 5.4 km, no rhythm, no rest, just 874 m of vertical served at a punishing tilt. Respect the gradient, gear low, pace the opening, and let the 1844 m summit come to you.

Length: 5.4 km
Average gradient: 16.33%
Max gradient: 29.46%
Start: 970 m
Summit: 1844 m
Net gain: 874 m
Total ascent: 827 m
Category: HC