Grimselpass

Overview

Grimselpass is a hors catégorie climb, the hardest rung on the scale that runs HC, 1, 2, 3, 4. At 23.6 km it is a genuine long-haul effort, lifting you from a start elevation of 646 m to a summit at 2163 m. The average gradient of 6.44% never sounds intimidating in isolation, but held across nearly the full length of the climb it becomes a relentless, grinding test of endurance. The headline number is the vertical: 1517 m of net elevation gain, with 1520 m of total ascent once the handful of flatter or descending sections are accounted for. There is almost nothing given back here — you climb what you climb.

How the Gradient Unfolds

The story of Grimselpass is consistency punctuated by sharp reminders. The 6.44% average is close to the whole truth of the road, meaning long stretches settle into a steady, sustainable rhythm rather than lurching between wall and false flat. That said, the maximum gradient touches 14.96%, more than double the average, so there are pitches that bite hard. Expect these ramps to appear where the road wrestles with the terrain, forcing you out of your seated cadence and into a fight. Because net gain (1517 m) and total ascent (1520 m) sit only 3 m apart, you can trust that virtually every metre of the 23.6 km is spent going up — there is no meaningful recovery descent to plan around.

Pacing Notes

On a climb this long, discipline in the opening kilometres is everything. Riding to your FTP rather than to your ego is the difference between cresting strong and blowing up with the summit in sight. Aim to sit just below threshold on the steady 6.44% sections and reserve headroom for the 14.96% ramps, where power will naturally spike whether you want it to or not. If you do not know your threshold, spend two minutes with the FTP estimator before you plan your effort — pacing 23.6 km blind is how riders detonate. Break the 1517 m of gain into thirds and check in with your legs at each mark.

Gearing

For an HC climb of this length and steepness, gear low and gear generously. A compact chainring paired with a wide-range cassette is the sensible baseline: a 34×32 will carry most fit riders through the sustained 6.44% grade, but the 14.96% maximum sections argue strongly for a 34×34 to protect your knees and keep cadence alive over 23.6 km. If your bike allows an even larger sprocket, do not be proud about using it — spinning up 1520 m of ascent always beats muscling it.

Summary

Grimselpass is a long, honest HC climb: 23.6 km of steady 6.44% gradient, sharpened by 14.96% ramps, delivering 1517 m of net gain from valley to pass. Pace it patiently, gear it low, and respect the distance.

Length: 23.6 km
Average gradient: 6.44%
Max gradient: 14.96%
Start: 646 m
Summit: 2163 m
Net gain: 1517 m
Total ascent: 1520 m
Category: HC