Il Colletto

Overview

Il Colletto is one of those climbs whose numbers tell you everything and warn you about nothing. Over 10.5 km it averages a punishing 9.89%, hauling you from a start elevation of 234 m up to a summit at 1274 m. That is 1040 m of net elevation gain — and with 1008 m of total ascent, this is a climb that rarely relents, offering almost no false-flat recovery on the way up. Rated HC, hors catégorie, the hardest classification cycling uses, it earns the label honestly. There is no sitting in the wheel and coasting here: the average gradient alone puts it among the steepest sustained efforts you will ever tackle.

How the Gradient Unfolds

The defining feature of Il Colletto is not a single wall but the sheer consistency of its severity. A 9.89% average across 10.5 km means the slope almost never dips into comfortable territory. Where lesser climbs give you a shallow kilometre to shake out your legs, this one keeps the pressure on continuously. The maximum gradient of 20.59% marks the cruelest pitch — more than double the average — and when the road tilts to that angle, even a light spin becomes a grind. Because total ascent (1008 m) sits just below net gain (1040 m), you can infer there is virtually no descending or flat within the climb: nearly every metre gained is a metre you keep. Expect the steepest ramps to arrive without much warning and to demand everything you have left.

Pacing Notes

On a climb this uniformly steep, pacing is survival. Anchor your effort to your FTP rather than to feel, because the 9.89% average will tempt you to over-push early and blow apart before the summit. Aim to hold a steady, sustainable power from the base and resist surging on the shallower sections — there are precious few of them. When the road hits 20.59%, accept that your speed will crater; keep your cadence alive and your effort just under threshold so you do not go anaerobic on the worst pitches. If you are unsure what your sustainable number is, run the FTP estimator before you ride and build your target around it. Over 10.5 km with 1040 m to gain, discipline in the first half is what lets you survive the second.

Gearing

Do not under-gear for Il Colletto. With a 9.89% average and ramps to 20.59%, this is compact-plus-wide-cassette territory. A 34×32 is the sensible minimum for strong climbers, but on a climb that never eases and spikes past 20%, most riders will be grateful for a 34×34 to keep the cadence turning on the steepest ramps. If your equipment allows an even easier bailout gear, use it — protecting your knees and your composure over 1040 m of near-continuous climbing is always worth the extra sprocket.

Summary

Il Colletto is a relentless HC test: 10.5 km with no meaningful respite, a savage 9.89% average, and a summit that rewards patient, well-paced climbing. Gear low, pace to your FTP, and ride the first half with restraint.

Length: 10.5 km
Average gradient: 9.89%
Max gradient: 20.59%
Start: 234 m
Summit: 1274 m
Net gain: 1040 m
Total ascent: 1008 m
Category: HC