Bike Speed Calculator Watts

Speed Calculation Formula:

\[ Speed = \left(\frac{power}{weight \times gravity \times \sin(slope) + rolling\_res + aero\_drag}\right)^{1/3} \]

Power:

Weight:

Slope:

radians

Rolling Resistance:

Aerodynamic Drag:

Speed:

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1. What is the Bike Speed Calculator?

The Bike Speed Calculator estimates cycling speed from power output, taking into account factors like weight, slope, rolling resistance, and aerodynamic drag.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ Speed = \left(\frac{power}{weight \times gravity \times \sin(slope) + rolling\_res + aero\_drag}\right)^{1/3} \]

Where:

\( power \) — Power output in watts (W)
\( weight \) — Total weight (bike + rider) in kg
\( gravity \) — 9.81 m/s²
\( slope \) — Road slope in radians
\( rolling\_res \) — Rolling resistance in newtons (N)
\( aero\_drag \) — Aerodynamic drag in newtons (N)

Explanation: The formula calculates the equilibrium speed where the power output equals the sum of all resisting forces.

3. Importance of Speed Calculation

Details: Understanding the relationship between power and speed helps cyclists optimize training, predict performance, and plan pacing strategies for races or events.

4. Using the Calculator

Tips: Enter all values in the specified units. For accurate results, measure rolling resistance and aerodynamic drag under typical riding conditions. Slope should be entered in radians (1° = 0.01745 radians).

5. Frequently Asked Questions (FAQ)

Q1: What is typical rolling resistance?
A: For road bikes on pavement, rolling resistance is typically 5-15N depending on tire type and pressure.

Q2: How to estimate aerodynamic drag?
A: Aerodynamic drag can be estimated as 0.5 × air density × frontal area × drag coefficient × speed², but for this calculator you need the drag force in newtons.

Q3: Why is slope in radians?
A: The trigonometric functions in programming languages typically use radians. Convert degrees to radians by multiplying by π/180.

Q4: What's a realistic speed for a given power?
A: On flat terrain, 200W might give 30-35 km/h for an average rider, while 400W might reach 40-45 km/h, depending on aerodynamics.

Q5: Does this account for acceleration?
A: No, this calculates steady-state speed where power equals resisting forces. Acceleration requires additional power.