Outils pratiques pour un travail de précision
Convertisseur Vitesse vers RPM
Convertissez la vitesse routière en régime moteur ou d'arbre de transmission, ou l'inverse, à partir du diamètre de pneu et d'un rapport de boîte.
Selected gear x final drive, or driveshaft ratio for a 1:1 direct check
RPM = speed (mph) x gear ratio x 336.14 / tire diameter (in). The "336.14" constant is the exact form of the commonly-rounded 336.
How it works
What this converts: enter a tire diameter and an overall gear ratio (the selected gear's ratio multiplied by the final-drive ratio, or 1 for a direct driveshaft-to-wheel check), then either a road speed to find the resulting RPM, or an RPM to find the resulting road speed.
Formula. RPM = MPH × gear ratio × (336.14) ÷ tire diameter (inches). The constant comes from converting miles-per-hour into inches travelled per minute (63,360 ÷ 60) and dividing by π to turn that into wheel revolutions - it's the precise version of the 336 constant used in most driveline reference charts.
Example. A 26-inch tire with a 3.55 overall ratio at 60 mph turns about 2754 RPM.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Solve for
- RPM from speed
- Tire diameter
- 26 in
- Overall gear ratio
- 3.55
- Road speed
- 60 mph
- Engine/driveshaft RPM
- 2500 rpm
Primary result: RPM: 2754 rpm.
Before using the result
- Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
- Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
- When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.
Limitations
This is drivetrain gearing math only, not a tire-fitment check. It assumes no wheelspin, converter or clutch slip, and that the tire diameter entered is the actual rolling diameter rather than the nominal sidewall figure. For a full multi-gear plan across an entire transmission, use the Gear Ratio, Road Speed & RPM Planner instead.
Frequently asked questions
What gear ratio should I enter for a driveshaft RPM check?
Enter 1. That treats the ratio input as a pass-through, so the result is wheel/driveshaft RPM directly rather than engine RPM through a transmission gear.
Why does a bigger tire lower RPM at the same speed?
A larger tire covers more ground per revolution, so it needs fewer revolutions - and therefore lower RPM through a fixed gear ratio - to cover the same distance in the same time.
Should I use nominal or measured tire diameter?
Measured (loaded/rolling) diameter gives a more accurate result. Nominal sidewall diameter is close but real tires rarely match it exactly.
Outils associés
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Comparez deux tailles de pneus côte à côte : diamètre, flanc, circonférence et effet sur le compteur de vitesse.
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Comparez une configuration roue/pneu actuelle et proposée, et visualisez précisément l'évolution de la géométrie.
Tailles Pneus Alternatives
Trouvez des tailles de pneus standard, y compris avec des diamètres de jante différents, qui conservent un diamètre total dans une tolérance choisie par rapport à une taille de départ.