Col de la Croix de Fer: Cycling Climb

The climb · France

About Col de la Croix de Fer

Collections

The 20 climbs most frequently featured in the Tour de France

The Croix de Fer approach recorded here begins above the Lac du Verney, on the Oisans side, and climbs towards Le Rivier d’Allemond. Over roughly 25 kilometres, its character keeps changing. The valley road gains height, then gives some of it back beyond Le Rivier, so the effort comes in chapters rather than one uninterrupted ascent. That descent is a genuine part of the route: the next uphill section asks you to find your climbing rhythm again.

Higher up, the Lac de Grand’Maison changes the scale of the surroundings. The enclosing valley opens towards alpine pasture, with the water and the higher slopes giving the ride a broader horizon. Another dip in the upper route prevents the summit from feeling like a simple continuation of the opening climb. By the final approach, the accumulated changes of gradient matter more than the average suggests. It is a substantial, varied way into the high mountains.

01 / The ascent

Elevation profile

Start 796 m · Summit 2,079 m

Gradient by distance24.86 km / 1,461 m gain

0 km5 km9.9 km14.9 km19.9 km24.9 km

02 / The crux

Where it gets difficult

Choose a distance to find the steepest continuous section of the climb.

Steepest 500 m average

14.1%

Where to find it

13.20–13.70 km from start

Net height gained: 71 m
Section length: 500 m

The whole climb24.86 km

0 kmFinish

03 / The numbers

Climb statistics

Distance: 24.86 km
Elevation gain: 1,461 m
Average gradient: 5.1%
Climb category: HC
Start elevation: 796 m
Summit elevation: 2,079 m

Current weather

At the climb start

Loading weather…

Weather data: MET Norway

04 / Your effort

How long would it take?

Enter the power you could hold for the whole climb. We calculate a moving time from the elevation profile and the forces you ride against.

Sustained power

W/kg

Use your intended climbing effort, rather than FTP unless you can hold it for the predicted duration.

Rider weight (kg)

Bike + kit weight (kg)

Bike + kit includes clothing, bottles and luggage.

Advanced settings

Defaults represent a road-bike scenario. Adjust these settings to match your tyres, drivetrain and riding position.

Effective drag area (CdA) (m²)

Rolling resistance (Crr)

Drivetrain efficiency (%)

Modelled moving time

1 h 46 min

Power throughout: 225 W
Average speed: 14.0 km/h

Based on the 24.86 km elevation profile. Assumes steady power, with no stops, braking or drafting. Rounded to the nearest minute.

The science behind the calculation

For each part of the stored profile, we solve the steady-state cycling power equation for speed, then add distance ÷ speed across the climb. Gravity uses rider + equipment weight; available power is W/kg × rider weight. This uses the profile’s distance and elevation together, without mixing in another route’s metrics.

Power × efficiency = gravity + rolling resistance + air resistance + bearing losses

The resistance equations are adapted from Martin et al. (1998), Validation of a Mathematical Model for Road Cycling Power. Air density changes with profile altitude using NASA’s standard-atmosphere model. This calculator’s adaptation has not been independently validated.

It predicts travel at the power you enter, including on descents. It does not model acceleration, cornering, braking, traffic, wind, changing weather or fatigue. At altitude, choose power you can sustain there: thinner air reduces drag, but this model does not predict its effect on your ability to produce power. Profile quality and assumed equipment settings also affect the result.

05 / On the ground