Rule 28 · Performance Lab
Rolling Resistance Calculator.
Test two setups — tyres, pressures, or surfaces — in the same position on the same road, and we'll back-calculate the Crr for each. This is the companion to the Aero Calculator: that one isolates drag, this one isolates rolling resistance.
01Your tests
Keep your body position and equipment identical between runs — only the thing you're testing should change. Calm conditions matter more here than for the aero test.
Test A
Test B
This method holds CdA constant and solves for Crr, so keep position and kit identical between runs. 0.32 m² is a typical hoods position — if you've run our Aero Calculator, use your own number here instead. Sea-level air density is 1.225.
02The comparison
Your coefficient of rolling resistance for each setup — this is what tyre choice, pressure, and surface actually move.
| Setup | Power | Speed | Crr | RR power |
|---|
03What the gap is worth
Same two numbers, translated into a race result.
A simplified Chung method: Crr is back-calculated assuming a constant CdA and air density between the two runs, so any difference in aerodynamic drag between them (a different body position, clothing, or wind) shows up here as if it were rolling resistance. Test in calm conditions (under 5 km/h wind, or use an out-and-back course), keep position and kit identical, and treat this as a strong estimate for the surface you tested on, not a lab-grade absolute.