Colle della Gragliasca

Overview

The Colle della Gragliasca is not a climb you talk yourself into on the day — it demands respect from the first pedal stroke. Over 15.3 km it climbs from a valley floor at 317 m to a summit of 2209 m, a net elevation gain of 1892 m. That works out to an average gradient of 12.34%, a figure that puts it firmly in hors catégorie (HC) territory, the hardest rung on the classification ladder above categories 1, 2, 3, and 4.

To put the numbers in perspective: a 12.34% average sustained for over fifteen kilometres is savage. Most riders never encounter an average that steep over any meaningful distance. Add a maximum gradient of 35.02% and you have a climb that punishes complacency at every turn.

How the Gradient Unfolds

The headline is the relentlessness. With an average of 12.34% and a total ascent of 1843 m across 15.3 km, there is very little respite built into this climb. The 1843 m of total ascent sits just below the 1892 m of net gain, telling you almost the entire route trends upward — there are no long descents to recover, no false flats to soft-pedal.

The defining feature is the max gradient of 35.02%. A ramp that steep is close to the limit of what a road bike can be ridden up seated, and it will spike your effort far above anything sustainable. Expect the road to lurch between merely brutal double-digit pitches and these near-vertical walls. The gap between the 12.34% average and the 35.02% max is the story: the climb constantly threatens to break your rhythm, and the discipline is in refusing to let the steepest ramps blow your legs apart before the summit at 2209 m.

Pacing Notes

On a climb this steep, pacing is everything. The temptation is to attack the early slopes while you feel fresh, but 15.3 km at 12.34% will expose that mistake long before the top. Ride to a power ceiling anchored to your FTP and treat the 35.02% ramps as unavoidable surges to absorb, not efforts to chase.

If you don't know your threshold, estimate it first with the FTP estimator, then set a target you can hold for the full climb. Because you gain 1892 m from bottom to top, thinning air near the 2209 m summit will quietly trim your sustainable power — bank a small margin early rather than emptying the tank on the lower slopes.

Gearing

Do not under-gear this climb. With a 12.34% average and pitches touching 35.02%, you want the lowest ratio you can bolt on. A compact 34-tooth chainring paired with a wide cassette is the minimum sensible setup. A 34×32 will get many strong riders up, but on the 35.02% walls you will be grinding at very low cadence.

For most riders a 34×34 is the smarter choice, giving you a little more room to spin through the steepest ramps and protect your knees over 15.3 km of climbing. If your bike accepts an even larger sprocket or a sub-compact crank, use it — there is no such thing as too easy a gear here.

Summary

The Colle della Gragliasca is a true hors catégorie test: relentlessly steep, unusually long for its gradient, and topping out high enough that altitude adds its own tax. Pace it to your threshold, gear it generously, and treat the summit at 2209 m as the reward for disciplined restraint.

Length: 15.3 km
Average gradient: 12.34%
Max gradient: 35.02%
Start: 317 m
Summit: 2209 m
Net gain: 1892 m
Total ascent: 1843 m
Category: HC