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Entering all relevant data: Enter gearing data manually for a bike not yet in the presets

Although a bike is not in the presets, you can still calculate its gearing if you know all the relevant data and enter it manually in to the fields.

  • Go to the main page
  • Press the Reset button to clear all input.
  • Start entering all these fields

  • Enter the first field en press Tab to get to the next and so on.

Remark: Only field 'Tire Circumference' will be filled automatically after filling the Rear Tire size fields

While not all field are filled, you might get some strange values (like NaN) in the resulting tables and even in the fields you are entering: Do not, worry it will be alright in the end.

Explanation for each field:

Primary Drive Ratio: this is the gear ratio between engine RPM and the clutch shaft RPM. It has to be entered as a decimal number like '1.761'. So if the User Manual says Primary Drive is '37/21', just calculate the result of 37 dived by 21 and enter the result (which is 1.761)

Rear Tire Size: The (Rear) tire size consists of 3 fields, the tire width in millimeter, the tire height in % of tire width and the rim diameter in inches. Not very consistent but that's the way tire manufacturers do it. An example is: 190/50/15. This means 190 mm wide, 50% of 190 mm and a 15" rim. If your bike is older and has tires that uses another notation, you have to convert those numbers to this notation and units.

Tire Circumference: The previous 3 fields are used to calculate the rear tire circumference which is used in all GC calculations. If you know that your tire circumference is different from a default calculated one, you can change the calculated one to your actual circumference. Make sure to use the right units. More info on this: Tire size and Circumference

M.P.RPM: This is the RPM where your bike delivers the most power. This RPM is often referred to by "Maximum power xxx BHP @ xxxx RPM" and is the RPM present at the top of the power curve. So try to find a bike review where these figures are mentioned. It is NOT the red-line RPM on your rev counter nor is it the RPM the rev limiter kicks in ! Also have a look at: Max RPM discussion

Final Drive Ratio: The number of teeth on the front and the number of teeth on the rear sprocket

Chain or Belt Pitch: the pitch of the stock chain in millimeters. All 520, 525 and 530 chains have a pitch of 15.875 mm (or 0.625 inch) If you're not certain, just mention the chain type (like '525'). (Not mandatory but please check User Manual).
For belt driven bikes please enter the pitch (not the width) of the belt. For most bikes this will be 14 mm but please try to find confirmation first.

Chain Links or Belt Teeth: The number of links in the stock chain. (Not mandatory but please try to find out in your user or service manual).
For belt drive bike please enter the number of belt teeth of the stock belt.

1st Gear Ratio: The number of teeth on the first gear cogwheels. Mostly these are listed in the user or service manual as "37 / 13". This is the preferred way as this is more accurate then supplying a rounded ratio.

Fill in like this: 
The first field is used for the number of teeth of the wheel that the power is being applied to, or in other words, of the wheel that is driving the second wheel. The second field is used for the number of teeth of the wheel that is being driven.

But sometimes gear ratio is only listed as the real ratio, that is 37 divided by 13 = 2.846 If so, you can enter 2.846 in the first field en 1 in the second field. This is not as accurate the other method (37 & 13) as it is rounded.
Like this:
Here also the first field is used for the wheel that the power is being applied to and thus is driving the second wheel.

2nd Gear Ratio - 7th Gear Ratio: The same way as the first gear ratio data was filled.
For Non-existing gears just enter 0 in both fields.

Fill all fields until you have something like this:

  • The first field of every Gear Ratio (with blue border) is used for the number of teeth of the cog-wheel that the power is being applied to, or in other words, of the cog-wheel that is driving the second wheel.  The second field (with red border) is used for the number of teeth of the cog-wheelthat is being driven.

    In this example I changed from a 190/50/17 to a 180/55/17 tire and also from a 15 to 14 front sprocket in Current setup and from a 36 to 39 rear sprocket in Custom setup.
  • You have to enter the value of the 'Chain Pitch' in 'mm' for now. When ready you can switch to inches by selecting the Units radio button. Normally a 520 and 530 chain has a 0.625 inch pitch which in millimeters is: 15.875 mm
  • Select the correct units if needed

  • Do NOT:
    press the Reset button
    - press the Load Gearing or Load Personal button
    - switch to another page and return or....................
    all your input will be lost !
  • Just use the calculator as intended, that is change various fields and see the results in the tables.

Saving Personal Setup's:
You can only save a Personal Setup for bikes that are already in the database so that button is grayed out when entering the data manually. If you want to be able to save & load Personal Setup's for a bike, send in the stock data (using the 'Add Bike' option from the menu) to have me add it to the database.

Next: Saving Personal Setup for future loading

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