Col du Grand Saint-Bernard

Overview

The Col du Grand Saint-Bernard is a genuine hors-catégorie test, the kind of climb that rewards patience over aggression. From a start elevation of 586 m it grinds all the way up to a 2475 m summit — a net elevation gain of 1889 m spread across 30.7 km of road. The average gradient sits at 6.15%, and while that figure sounds humane on paper, the sheer length is what defines the effort. This is not a climb you attack; it is a climb you manage, kilometre by kilometre, until the thin air near the top starts doing the pacing for you.

How the Gradient Unfolds

At 6.15% average over 30.7 km, the Grand Saint-Bernard is a steady-state effort punctuated by sharper ramps. The maximum gradient touches 13.1%, more than double the average, so the road clearly is not uniform — expect flatter recovery sections that let the legs breathe, offset by pitches where the slope roughly doubles and forces a hard gear change. The gap between the 1889 m net gain and the 1869 m total ascent is only 20 m, which tells you there is almost no descending or false-flat relief along the way. Once you start climbing, you keep climbing. Plan your effort around the steeper 13.1% ramps rather than the gentle average, because those are where riders overcook and pay for it later.

Pacing Notes

The single biggest mistake on a 30.7 km climb is starting too hard. Anchor your effort to your FTP: on a climb this long, most riders should sit comfortably below threshold for the opening two-thirds, then decide how much to spend once the summit is in reach. If you are unsure of your number, run it through the FTP estimator before you go, so your power targets on the 6.15% grind are grounded in something real rather than optimism. Treat the 13.1% ramps as short, deliberate surges — get over them without spiking your effort, then settle straight back into rhythm. With 1889 m to gain, even a small early over-pace compounds badly across half an hour or more of climbing.

Gearing

For an HC climb that averages 6.15% and spikes to 13.1% over nearly 31 km, gear low and gear generously. A 34×32 is the minimum I would take on this: it gives you a spinning cadence for the long steady stretches and just enough range for the steeper pitches. If you know you fade on sustained climbs, or you are riding it at the end of a long day, step up to a 34×34 — the extra sprocket is cheap insurance against grinding to a walking cadence high on the mountain, where the altitude near 2475 m robs your legs of their usual punch. On a climb this long, protecting your knees and your rhythm matters more than saving a few grams.

Summary

The Col du Grand Saint-Bernard is a patience climb: 30.7 km, a 6.15% average, and a 1889 m net gain that leave no room for early heroics. Respect the 13.1% ramps, pace off your FTP, gear low, and let the summit come to you.

Length: 30.7 km
Average gradient: 6.15%
Max gradient: 13.1%
Start: 586 m
Summit: 2475 m
Net gain: 1889 m
Total ascent: 1869 m
Category: HC