From Saint-Jean-de-Maurienne to the Col de la Croix de Fer (6,781 ft / 2,067 m) it is 17.5 miles (28.1 km) at an average of 5.5% with 5,062 ft (1,543 m) of climbing, according to Climbfinder; Wikipedia gives 18.3 miles (29.5 km) at the same 5.5% average. It is a very long climb, with flats and descents along the way.
What the climb is like
It is not a steady climb. It alternates 9-10% sections with flats and even descents, so the climbing you actually do is more than the elevation difference between the start and the top (CyclingCols counts 5,397 ft / 1,645 m in total). The breaks are deceptive: after each one you have to find your rhythm again. The D926 has tunnels, and there is a scenic alternative via Saint-Jean-d’Arves.
A note on the numbers
The sources do not fully agree: Climbfinder gives 17.5 miles (28.1 km) and 5,062 ft (1,543 m); CyclingCols 18 miles (29 km) and 5,397 ft (1,645 m), counting the short descents; and Wikipedia 18.3 miles (29.5 km). The top is at 6,768-6,781 ft (2,063-2,067 m) depending on the source, and the maximum grade between 9.5 and 12%. We use Climbfinder and Wikipedia’s average, and we do not publish a segment profile or a starting elevation.
Its history in the Tour de France
The Tour first climbed it in 1947 (Fermo Camellini crossed first) and has crossed it 22 times. Riders first over the top include Gino Bartali (1948), Fausto Coppi (1952), Bernard Hinault (1986), Richard Virenque (1995) and Giulio Ciccone (2022). The Tour often uses it to link the Maurienne with Alpe d’Huez, as in 2022.
When to go, water and traffic
It closes in winter; we could not find official dates, so check before you go. Because of the tunnels, use front and rear lights. The road is not a dead end: it continues past the Grand’Maison reservoir toward Allemont and Le Bourg-d’Oisans, or turns off to the Col du Glandon.
What gearing to use
The average is moderate, but the 9-10% sections and the length call for a 34x28 or 34x30. At 3 W/kg (watts per kilogram of body weight) and 159 lb (72 kg), you ride about 5.6 mph (9 km/h) on 10%, which on a 34x30 is 63 rpm. Compare in the gear calculator.
Tips
- It is almost two hours for a recreational rider: carry enough food.
- Use the descents to drink and eat, not to attack.
- If you want it harder, climb via the Glandon from La Chambre.
Frequently asked questions
How long does it take to climb the Croix de Fer from Saint-Jean-de-Maurienne?
A 159 lb (72 kg) rider on a 21 lb (9.5 kg) bike takes about 1 hr 54 min at 3 W/kg (216 W), 2 hr 14 min at 2.5 W/kg and 1 hr 29 min at 4 W/kg. Work out your own time with your weight and power in the calculator on this page.
What is the hardest side of the Croix de Fer?
The one from La Chambre via the Col du Glandon: 14.1 miles (22.7 km) at 7%, according to Wikipedia. The Saint-Jean-de-Maurienne side is longer but gentler (5.5%).
Are there tunnels on the way up the Croix de Fer?
Yes, on the D926. Bring front and rear lights.