Col de Jambaz: Cycling Climb

The climb · France

About Col de Jambaz

From the Brevon valley, the approach to Col de Jambaz runs south through Bellevaux towards the pass. This is a modest Alpine pass, with village roads and inhabited slopes setting the tone. The selected ascent covers about 6.8 kilometres, averaging 3.8%, so its character comes from sustained climbing without the severe overall gradient of the larger passes nearby.

Bellevaux gives the ride a clear geographical anchor, while the col supplies a natural destination beyond the village. The effort is long enough to settle into, yet compact enough to sit comfortably within a wider ride through the Chablais. There is no need to attach a detour to Lac de Vallon to complete this ascent: the pass and the lake are separate destinations. Jambaz offers a measured introduction to the area's climbing, with an ordinary mountain road doing most of the work.

01 / The ascent

Elevation profile

Start 764 m · Summit 1,025 m

Gradient by distance6.81 km / 262 m gain

0 km1.4 km2.7 km4.1 km5.4 km6.8 km

02 / The crux

Where it gets difficult

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

Steepest 500 m average

5.6%

Where to find it

4.10–4.60 km from start

Net height gained: 28 m
Section length: 500 m

The whole climb6.81 km

0 kmFinish

03 / The numbers

Climb statistics

Distance: 6.81 km
Elevation gain: 262 m
Average gradient: 3.8%
Climb category: 3
Start elevation: 764 m
Summit elevation: 1,025 m

Current weather

At the climb start

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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

21 min

Power throughout: 225 W
Average speed: 19.4 km/h

Based on the 6.81 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