Boar Hill Coldharbour Lane: Cycling Climb

The climb · United Kingdom

About Boar Hill Coldharbour Lane

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Simon Warren’s Another 100 Greatest Cycling Climbs

Coldharbour Lane heads south out of Dorking towards the higher country on the approach to Coldharbour. This section covers about 3.1 kilometres, following a winding line with changes of slope rather than offering a single uniform ramp. The distance gives the climb room to develop, and the road's bends prevent the finish from becoming one fixed point on the horizon.

The effort arrives unevenly. A relatively mild stretch can be followed by firmer climbing, and the middle of the stored profile carries a particularly marked rise. Easier portions interrupt the work without bringing the ascent to an end; the final part still gains height. Those changes make the ride feel like a progression through successive folds in the hillside. The road reaches higher ground here, rather than the summit of Leith Hill itself. A varied approach with a more substantial feel than its opening suggests.

01 / The ascent

Elevation profile

Start 89 m · Summit 230 m

Gradient by distance3.11 km / 147 m gain

0 km0.6 km1.2 km1.9 km2.5 km3.1 km

02 / The crux

Where it gets difficult

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

Steepest 500 m average

11.3%

Where to find it

1.40–1.90 km from start

Net height gained: 56 m
Section length: 500 m

The whole climb3.11 km

0 kmFinish

03 / The numbers

Climb statistics

Distance: 3.11 km
Elevation gain: 147 m
Average gradient: 7.1%
Climb category: 4
Start elevation: 89 m
Summit elevation: 230 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

11 min

Power throughout: 225 W
Average speed: 16.3 km/h

Based on the 3.11 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