Col de Tende Road Tunnel

Overview

The Col de Tende Road Tunnel is a long-haul Category 1 climb that rewards patience over punch. Over 25.2 km it lifts you from a valley floor at 629 m to a summit of 1861 m, an average gradient of 4.89% that never lets you settle but rarely bites hard either. The headline number is duration: at more than 25 km, this is a climb measured in tens of minutes, not a handful of ramps. With a net elevation gain of 1232 m and a total ascent of 1216 m, almost every metre you climb stays climbed — there is very little false descent to give the legs a break. Treat it as a sustained tempo effort rather than a series of attacks, and the length becomes an ally instead of an enemy.

How the Gradient Unfolds

A 4.89% average across 25.2 km describes a road that leans gently but relentlessly. The gap between the 1232 m net gain and the 1216 m total ascent is small — just 16 m — which tells you the profile is almost monotonically uphill, with barely a flat or downhill section to interrupt the rhythm. That consistency is the defining feature. Because there is no reliable respite built into the road, you cannot rely on recovery stretches to bail out an over-cooked start. Expect the grade to hover around its average for long, uniform stretches, so the challenge is mental as much as physical: holding a smooth cadence and steady output while the summit at 1861 m stays a long way off.

Pacing Notes

On a climb this long, pacing discipline decides your day. Anchor your effort to a percentage of your FTP rather than to how you feel in the first few kilometres — the length flatters early enthusiasm and punishes it later. A sustainable target for a climb of roughly this duration sits comfortably below threshold, leaving margin for the final third when fatigue compounds. If you are not sure what your threshold is, run the numbers through the FTP estimator before you ride so your power targets are grounded in real data. Break the 25.2 km into mental thirds and check in at each: if you are still holding your target power in the last third, you paced it well.

Gearing

The gradient here is moderate, but the sheer 25.2 km means your gearing needs to protect your legs from the accumulated load rather than survive a single steep wall. A compact 34-tooth inner chainring paired with a 34×32 low gear will let most riders spin the 4.89% average without grinding. If you carry extra fatigue, ride at a lower cadence, or want insurance for the back half of the climb, step up to a 34×34 — the extra sprocket costs nothing on the flat and buys a lower floor when the legs fade past 1232 m of climbing. Prioritise a cadence you can hold for the full ascent over a bigger gear you can only push fresh.

Summary

The Col de Tende Road Tunnel is a test of sustained tempo: long, consistent, and unforgiving of a fast start. Pace to your threshold, gear low enough to spin, and let the 25.2 km come to you.

Length: 25.2 km
Average gradient: 4.89%
Max gradient: n/a
Start: 629 m
Summit: 1861 m
Net gain: 1232 m
Total ascent: 1216 m
Category: 1