Colle_Intersile

Overview

Colle Intersile is a hors catégorie climb that does not bother with a warm-up. Over 14.9 km it averages 9.82%, a number that would be punishing on a five-kilometre wall and is genuinely severe stretched across this distance. You start at 931 m and finish at 2397 m, a net elevation gain of 1466 m, while the total ascent of 1488 m tells you the road barely dips along the way — almost every metre you gain, you keep. The category label says it all: this is the hardest tier there is, and the numbers earn it.

How the Gradient Unfolds

The defining feature here is relentlessness. A 9.82% average over 14.9 km means there is no long false-flat to recover on, and the gap between the net gain of 1466 m and the total ascent of 1488 m — just 22 m of give-back across the entire climb — confirms it. The road tilts up and stays up.

Layered on top of that steady severity is a 28.68% maximum gradient. That figure is nearly three times the average, so expect at least one pitch that forces you out of any comfortable rhythm and demands a short, brutal effort. Because the base gradient never eases, those ramps arrive when your legs are already loaded, which is what makes the climb feel harder than its average alone suggests.

Pacing Notes

Discipline wins here. On a climb this long and steep, going into the red early costs you far more than it does on a shorter effort. Anchor your pacing to your FTP and aim to sit just below it on the sustained sections, holding a wattage you can defend for the better part of an hour rather than chasing a number you can only hold for ten minutes. If you are unsure where your threshold sits, run the numbers through the FTP estimator before you commit to a pace.

Save a small reserve for the steepest ramps. When the road spikes toward its 28.68% max, you will briefly blow past threshold no matter how conservative you are — that is fine, provided you settle straight back down afterward. Treat those pitches as short surges, not the new normal.

Gearing

With a 9.82% average and a 28.68% max over 14.9 km, gear low and gear again. For most riders a compact 34-tooth chainring paired with a wide-range cassette is the sensible baseline. A 34×32 is the minimum you should consider here, and even then only if you have the fitness and low body weight to spin it. For nearly everyone else, a 34×34 is the smarter call — the extra sprocket buys you cadence on the sustained slopes and keeps the steepest ramps just about turnable. If your setup allows an even easier bailout gear, this is exactly the climb to have it.

Summary

Colle Intersile is an honest hors catégorie test: long, unremittingly steep, and topped by a genuinely high summit. Pace it off your threshold, gear generously, and respect the ramps.

Length: 14.9 km
Average gradient: 9.82%
Max gradient: 28.68%
Start: 931 m
Summit: 2397 m
Net gain: 1466 m
Total ascent: 1488 m
Category: HC