Rolling resistance is one of the hidden forces that slows down bikes, cars, wheelchairs, skateboards, and pretty much anything that rolls. This calculator helps you estimate how much force and power are needed to overcome it, so you can make better decisions about tires, pressure, speed, and efficiency.
Calculate Rolling Resistance
This tool calculates rolling resistance force as Frr = Crr × N, where N = m × g × cos(θ) and θ is based on grade.
What Is Rolling Resistance?
Rolling resistance is the energy loss that happens when a wheel deforms against a surface. Tires and road surfaces are not perfectly rigid, so some energy is continually turned into heat instead of forward motion. Even on flat roads, this resistance is always present and must be overcome by your legs, motor, or engine.
Formula Used in This Calculator
We use a standard engineering model:
- Normal force: N = m × g × cos(θ)
- Rolling resistance force: Frr = Crr × N
- Power loss due to rolling resistance: Prr = Frr × v
Where m is total mass, g is gravity, θ is road angle from grade, and v is speed in m/s.
Typical Crr Values
The coefficient of rolling resistance (Crr) depends heavily on tire construction, pressure, load, and surface roughness.
| Condition | Approximate Crr | Notes |
|---|---|---|
| Performance road bike tire on smooth asphalt | 0.0025 to 0.0040 | Low losses at optimized pressure |
| Typical commuter / touring bike setup | 0.0045 to 0.0070 | Real-world range for daily use |
| Passenger car tire on good pavement | 0.007 to 0.012 | Varies by tire compound and inflation |
| Gravel or rough mixed surface | 0.015 to 0.030 | Large increase in energy demand |
How to Use the Calculator
1) Enter total mass
Include rider + bike, driver + vehicle, or total loaded system mass. Small mass errors can noticeably change the result.
2) Choose or enter Crr
Use a preset for a quick estimate, or type your own value if you have test data.
3) Enter speed and grade
Speed changes power required, while grade slightly changes normal force through cos(θ). This calculator focuses on rolling resistance only, not climbing force or aerodynamic drag.
Worked Example
Suppose total mass is 85 kg, Crr is 0.005, speed is 25 km/h, and grade is 0%:
- Normal force N ≈ 85 × 9.80665 = 833.57 N
- Rolling force Frr ≈ 0.005 × 833.57 = 4.17 N
- Speed v = 25 / 3.6 = 6.94 m/s
- Power Prr ≈ 4.17 × 6.94 = 28.9 W
That means almost 29 watts are spent just to overcome rolling resistance, even before wind drag is considered.
How to Reduce Rolling Resistance
- Use tires with lower measured Crr.
- Keep tire pressure in an effective range for your weight and terrain.
- Use smoother surfaces when possible.
- Reduce unnecessary load mass.
- Maintain wheel bearings and alignment.
Important Limitations
This model is intentionally simple and useful for planning, but not a full vehicle simulation. Real-world rolling resistance can vary with temperature, tire hysteresis, pressure changes over time, casing design, and speed-dependent behavior. For precision work, use coast-down testing or lab-measured tire data.
FAQ
Does rolling resistance increase with speed?
The force is often treated as nearly constant at moderate speeds for a given setup, but the power needed increases with speed because power = force × speed.
Is rolling resistance bigger than aerodynamic drag?
At low speeds, rolling resistance can be a major part of total resistance. At higher speeds, aerodynamic drag usually dominates.
Can I use this for e-bikes and EVs?
Yes. The physics is the same. Just make sure the mass and Crr values reflect your specific tires and loading condition.