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Home > gear ratios
gear ratios
At BAKER, our lives are all about multiplying torque. It begins by mastering the math and ends with making sure you stay riding in the best range possible...for the long haul.
This page explains GEAR RATIOS. This is the art and science of optimizing the transmission gear sizes to the desired RPM-vs-Speed performance. The variables we finesse to achieve the perfect balance are the motor sprocket, the transmission gearset, the transmission pulley/sprocket, the wheel pulley/sprocket and the wheel size.
The fundamentals of this mastery reside with the following two equations:
RPM = (S × Sr × Pc × G × 88.00) ÷ (Tc × Sf × Pm)
Speed = (RPM × Tc × Sf × Pm) ÷ (Sr × Pc × G × 88.00)
Use the diagram below to determine what your speed or RPM will be.
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| S |
Speed (miles per hour) |
| RPM |
Engine revolutions per minute |
| Sr |
Rear sprocket tooth count, secondary drive |
| Pc |
Clutch sprocket tooth count, primary drive |
| G |
Gear ratio |
| Tc |
Circumference of rear tire: (diameter (ft.) X 3.1416)
Typical tire is 25” in diameter
Example: 2.083ft. (25”) X 3.1416 = 6.54ft. |
| Sf |
Front pulley/sprocket tooth count
(tranny output, secondary drive) |
| Pm |
Motor sprocket tooth count, primary drive |
Now that you have the equation (above) to fine tune your drivetrain. Let's go deeper. Let's add to the math by introducing you to more variables to the equation: The gearbox ratios. Many treat it as Pandora's box for a reason. But we'll coach you through.
Below is a list links that lead pages that have more details about our transmission gearsets that fit within the Harley-Davidson transmission cases. In these pages the gear ratios for the according BAKER transmission will be displayed so you have the knowledge to make the best choice for your bike.
At BAKER Drivetrain we notice for some reason a lot of bikers don't do math. How odd. Now some do it well, but many don't. So, we're here to help you through this part.
- Feel free to TOLL FREE at 1-877-640-2004 and get advice on how to optimize your drivetrain performance.
- Get a hardcopy by calling us or filling the form on the home page. Or just download a PDF of it with the link below. It have some examples that may apply to your configuration. The download is worth the hope of a ready-made answer!
Download PDF of Pages 46-47
(1mb) here
(If your Pop-up Blocker in enabled, you may have to hold down your "CTRL" key on the bottom/left of your keyboard to get this link to work).
- on our RPM vs. Speed Calculator. This popular online tool allows you to finesse, massage, and work the numbers up and down until you reach the desired effect.
Launch the BAKER RPM vs. Speed Calculator
(If your Pop-up Blocker in enabled, you may have to hold down your "CTRL" key on the bottom/left of your keyboard to get this link to work).
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