Col de la Croix de Fer: 29 km from Saint-Jean and how to ride its broken rhythm

The Col de la Croix de Fer is 2,067 m high, and from Saint-Jean-de-Maurienne it is one of the longest climbs in the Alps: 29.3 km and about 1,620 m of climbing, according to the Saint-Sorlin-d'Arves tourist office, which calls it the classic way up and a gentler one than the route over the Glandon. It is not a steady climb. It goes through a gorge, past a string of mountain villages, drops for a while, and only then settles into its last hard stretch. Here is how the road is built, how to ride its broken rhythm, and how to prepare for it on your trainer.

The climb, village by village

The route leaves Saint-Jean-de-Maurienne at the "Opinel" roundabout and follows the D926 up the Arvan valley all the way to Saint-Sorlin-d'Arves and the pass. The road is marked with milestones, so you always know where you are. The tourist office puts the ride at about two and a half hours.

• Saint-Jean to the Arvan gorge. The Route des Grandes Alpes guide warns that the first 4 km already reach 9%. Further on, around kilometres 11 and 12, the road goes through three tunnels in the gorge. The track on this page is 29.0 km, close to the official route, and its steepest kilometre is 10.2%.
• The Arves villages. Above the gorge the valley opens out through Saint-Jean-d'Arves and its hamlets, with the Aiguilles d'Arves ahead. This middle part is the most irregular. On our profile it includes a real descent of a couple of kilometres before Saint-Sorlin. Don't treat it as rest you have earned. It is the place to eat and drink before the finish.
• Saint-Sorlin to the pass. The last 6 km or so run at 8–9%, with one hairpin at 12–13%, according to the Route des Grandes Alpes. Our track agrees: from Saint-Sorlin every kilometre is between 7.6% and 9.8%. Up here you ride through high pasture, and the tourist office warns you may meet grazing herds on the road.

How to ride a climb that keeps changing

The Croix de Fer punishes riders who ride it like a single steady effort. The gradient keeps changing for the first 18 km. The final 6 km are the only part where you can settle into a rhythm, and they come after a long time in the saddle.

• Ride the first two-thirds by power, not by speed. Hold 75–80% of FTP on the climbing sections and let the flatter parts go by at an easy spin. Chasing speed through the villages is how you arrive at Saint-Sorlin with nothing left. Our guide to pacing a climb with power explains why the even effort wins.
• Save the real effort for Saint-Sorlin. If you still feel good there, those last 6 km are where to use it. It is also where the altitude starts to bite: above 1,500 m, the same effort gives fewer watts.
• Gear for the top, not the bottom. 8–9% for half an hour at the end of a two-and-a-half-hour climb calls for a compact and a 32 or 34 sprocket. See gearing for climbing.
• Lights for the tunnels. Fit a front and rear light, even on a bright day, for the tunnels in the gorge on the way up and on the way down.
• Use the water points. The tourist office lists water in Saint-Jean-de-Maurienne, Saint-Jean-d'Arves, Saint-Sorlin-d'Arves and at the pass. Saint-Jean and Saint-Jean-d'Arves also have bike repairers.

An iron cross and a long history in the Tour

The pass is named after the iron cross on a stone monument at the top. The road was built in stages: from Saint-Sorlin to the pass in 1900, then on to the Col du Glandon in 1912. It was inaugurated on 14 July 1912. The Route des Grandes Alpes counts 21 Tour de France crossings between 1947 and 2022.

The race came back in 2026. Stage 20 on 25 July, from Le Bourg-d'Oisans to Alpe d'Huez, crossed the Glandon and the Croix de Fer. The Savoie department closed the D926 over the top from the evening before, and the road from Saint-Sorlin down towards Fontcouverte-la-Toussuire was shut during the race.

When to go and how to make a day of it

• Season. The tourist office gives the season as June to the end of October, weather permitting. The top is above 2,000 m, so take a gilet and full gloves for the descent whatever the weather in Saint-Jean.
• At the top. There is a restaurant at the pass, and in summer both the Saint-Sorlin tourist office and the pass have charging points for e-bikes.
• The Glandon. The Col du Glandon is only about 3 km from the Croix de Fer. A loop over the top and down the Glandon side through Saint-Colomban-des-Villards brings you back into the Maurienne valley, where the valley road leads back up to Saint-Jean.
• Over to the Oisans. The south side drops to Allemond and Le Bourg-d'Oisans, at the foot of Alpe d'Huez. On a one-week trip, our first Alps trip guide shows how to fit several big passes in.

Ride it in Moveee Indoor

This route is the real road from Saint-Jean-de-Maurienne to the pass. In Moveee Indoor your smart trainer reproduces its gradient as you ride, and the world around you is built from map data of the Arvan valley. What the Croix de Fer teaches you indoors is restraint. The villages and the dip invite you to push, and the last 6 km show you whether you did. Ride it once, look at your power for the final section, and next time hold back more in the middle.

Your ride is saved with its power data, so you can compare one attempt with the next. If you would rather ride it on another device, download the GPX above.

The short version

29.3 km and about 1,620 m of climbing from Saint-Jean-de-Maurienne to 2,067 m, by the tourist office's numbers. The first two-thirds keep changing, with tunnels in the gorge and a dip before Saint-Sorlin, and the last 6 km run at 8–9%. Ride the middle gently, eat before Saint-Sorlin, bring lights for the tunnels, and save the real effort for the end.