Understanding Rolling Resistance
Rolling resistance is the force that resists wheel motion. It comes from tire flex, road texture, bearing losses, and small surface deformation. Electric vehicles feel this loss strongly because steady cruising uses limited battery energy. A lower coefficient means less force is needed to keep the vehicle moving.
Why The Coefficient Matters
The rolling resistance coefficient, often written as Crr, links normal load to rolling force. It has no unit. A small change can shift range, motor load, current draw, and heat. For example, a soft tire can raise the value. A rough floor can do the same. Heavy cargo also increases normal force, so the rolling force rises even when Crr stays constant.
Electrical Planning Uses
This calculator is useful when sizing motors, batteries, inverters, and wiring. It converts rolling force into mechanical power. It then estimates electrical power after efficiency losses. The voltage field helps estimate current. That current can guide fuse, conductor, and controller checks. It is not a substitute for certified design, but it gives a strong planning estimate.
Testing And Inputs
You can enter a known coefficient, a measured rolling force, or coastdown deceleration. The coastdown method estimates resistance from how fast speed falls. It can also subtract aerodynamic drag. That option helps when tests are done at higher speed. Low speed tests usually reduce air drag effects.
Grades And Surfaces
Road grade changes the total road force. Uphill grade adds force. Downhill grade can reduce required drive power. Surface choice also matters. Smooth concrete, asphalt, gravel, grass, and soft soil can produce very different results. Use measured data when accuracy matters.
Reading The Results
The result table shows coefficient, force, power, energy, and estimated current. Rolling power is only the tire related part. Total road power may include grade and aerodynamic drag. Electrical power includes efficiency and optional auxiliary load. Compare scenarios by changing load, speed, grade, or tire pressure. Export the results when documenting tests. Use conservative assumptions for real equipment. Always verify final choices with field measurements and safety standards.
For repeatable testing, record tire pressure, temperature, surface condition, and vehicle weight. Use the same route when comparing tires. Small notes prevent misleading comparisons later during future maintenance reviews.