Here are the 5 numbers that you'll need:
- C: The circumference of your right rear tire. We suggest the right rear because the result will be quite accurate even if you're running tire stagger on an oval track kart. You can use our E-Z Read Tire Stagger Tape or any other accurate, flexible flat tape measure to determine the tire circumference. We'll use 35 inches in our example.
- T1: The number of teeth on the driver sprocket. Let's assume 15 teeth for our example.
- T2: The number of teeth on the axle sprocket. Let's use 75 teeth for our example.
- RPM: The maximum engine RPM seen during the lap. We'll use 12,500 RPM.
- 1056: A conversion factor to convert Inches per Minute to Miles per Hour. If you're curious, this number results from dividing the number of inches in a mile (63360) by the number of minutes in an hour.
Here's the simple formula: Top Speed = (C x T1 x RPM) / (T2 x 1056)
Here's our example: Top Speed = (35 x 15 x 12500) / (75 x 1056) = 82.86 MPH
Here's how you would enter the formula in an Excel spreadsheet: =(35*15*12500)/(75*1056)
Here's how you would enter the formula on a standard handheld calculator: 35 'x' 15 'x' 12500 '/' 75 '/' 1056 '=' (replace '/' with your calculator's 'divide' button)
That's all there is to it!
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