Colle dell'Impiso

Overview

Colle dell'Impiso is a long, sustained category 1 ascent that runs for 17.6 km and averages 5.46%. From a start elevation of 666 m it winds up to a summit at 1625 m, a net elevation gain of 959 m. Because the road rises and dips along the way, the actual work is greater than the net figure suggests: total ascent comes to 1025 m, meaning you climb an extra 66 m that the net number hides. It is not a brutally steep climb on average, but its length and a single vicious pitch of 18.02% give it real teeth. This is a climb of patience rather than explosive power — you settle in, find a rhythm, and hold it for the better part of an hour.

How the Gradient Unfolds

The headline average of 5.46% is honest for most of the 17.6 km, but it flatters the hardest sections. With a maximum gradient of 18.02%, the climb clearly hides at least one ramp more than three times steeper than the average. Those steep pitches are offset by shallower stretches and the descents implied by the gap between the 959 m net gain and the 1025 m total ascent. Expect the profile to feel uneven: long stretches around the mid-single-digit average, punctuated by short walls that spike toward that 18.02% figure. The extra 66 m of climbing scattered across false-flats and dips is exactly what makes the road feel longer than a simple 959 m haul.

Pacing Notes

On a climb this long, discipline pays. Anchor your effort to your FTP and aim to spend most of the 17.6 km just below threshold, leaving headroom to absorb the 18.02% ramp without blowing up. If you do not know your threshold power, run the numbers first with the FTP estimator. The trap here is the average: 5.46% invites you to push hard early, but the steep pitches and rolling total ascent of 1025 m will punish anyone who has already emptied the tank. Ease into the first kilometres, stay seated where you can, and save a match for the steepest wall.

Gearing

For a 17.6 km climb topping out at 18.02%, gear low and gear early. A compact 34-tooth inner chainring paired with a 34×32 cassette is a sensible baseline for the sustained 5.46% grind, but the 18.02% pitch is where riders get caught over-geared. If you have it, a 34×34 gives you a genuine bailout for that ramp and lets you spin rather than grind over the top. Given the 959 m of climbing and 1025 m total ascent, the extra range is worth carrying — cadence protects your legs across a long day in the mountains.

Summary

Colle dell'Impiso rewards patience: a long category 1 climb where the modest 5.46% average masks an 18.02% wall and 66 m of hidden climbing between net gain and total ascent. Pace it below threshold, gear low, and let the 17.6 km come to you.

Length: 17.6 km
Average gradient: 5.46%
Max gradient: 18.02%
Start: 666 m
Summit: 1625 m
Net gain: 959 m
Total ascent: 1025 m
Category: 1