Boneyard Tools

The three forces every cyclist pedals against

How rolling resistance, aerodynamic drag and gravity share the load at different speeds and gradients, and what that means for going faster.

Open the Cycling Power Calculator →

Rolling resistance: the steady tax

Rolling resistance is the energy lost as your tyres flex against the road surface. It grows in direct proportion to speed and to the combined weight of you and the bike, scaled by the coefficient Crr. Because it rises only linearly, it is a modest and fairly constant share of your power at road speeds, often a few tens of watts. Supple tyres, higher quality casings and correct pressure all lower the Crr and shave watts for free.

Aerodynamic drag: the runaway cost

Air drag is the single biggest reason going faster feels so much harder. The power to overcome it rises with the cube of speed, so small increases in pace demand large jumps in wattage. In the flat examples above, moving from 30 to 40 km/h more than doubles the total power, and almost all of that extra effort is spent pushing air. Your frontal area and drag coefficient combine into CdA, and lowering it through position or equipment pays the biggest dividends at speed.

Gravity: the gradient multiplier

On the flat, gravity is neutral, but tilt the road and it becomes the dominant force. Climbing power depends on total mass, the steepness of the grade, and your speed, so a heavier rider or loaded bike pays more on every hill. This is why weight matters far more going uphill than on level ground, and why the climbing term in the calculator can exceed both drag and rolling combined once the gradient passes a few percent.

Reading the split to get faster

The power breakdown tells you where to spend your money and training. If air drag is the largest slice, aerodynamics is your lever: a tighter position, an aero helmet or narrower profile. If climbing dominates your usual rides, shedding system weight and building sustained power will help most. Rolling resistance rewards good tyres regardless of terrain. Matching the fix to the biggest bar is the quickest route to more speed for the same effort.

Frequently asked questions

At what speed does air drag overtake rolling resistance?

For a typical road setup it happens at fairly low speeds, often around 15 to 20 km/h, after which drag climbs away steeply while rolling stays modest. By 30 km/h on the flat, air drag is the clear majority of your power.

Does losing weight make me faster on the flat?

Only a little. On level ground weight affects rolling resistance, which is small, so the gain is minor. Weight matters far more on climbs, where gravity dominates the power equation.

Is CdA or Crr easier to improve?

CdA usually offers more headroom at speed because drag scales so steeply, and body position alone can change it a lot. Crr gains are real but smaller, and mostly come from tyre choice and pressure.