Road speed from wheel or engine RPM and overall tire diameter.
| Speed | – |
Use this for a speedometer check or a gearing sketch. Speed = RPM × π × diameter × 60 / 1000, with diameter in metres. 2500 RPM on a 632 mm tire is about 298 km/h if that RPM is at the wheel. With a gearbox, divide engine RPM by the overall gear ratio first. Diameter can be millimetres or inches; speed is shown in km/h or mph to match. Get overall diameter from the tire-size tool.
RPM: Revolutions per minute at the wheel, or engine RPM after the gear.
Diameter: Overall tire diameter.
Speed: Linear speed of the tread.
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