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Bicycle Gearing Diagrams

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Gear Selection Diagram

Gearing Diagram Click freewheel cog to see the gearing diagram in the gear calculators main window Click chainring cog to see the gearing diagram in the main window of the gear calculator

The GearCalc bicycle gear calculators gearing diagram is a vector based graphic representing a riders eye view of a set of derailleur bicycle gears. The example on the left shows three front cogs used with a nine cog cassette. The black line represents the chain. The rear cogs coloured in red are the ones that will not be used because a similar ratio can be obtained, with a straighter chain line by using a different combination of gears. The straighter the chain line means less lateral forces on the chain causing slightly less frictional losses

When you pass the mouse over the cogs, the mouse pointer changes to indicate that you can click on it and a tool tip appears to tell you how many teeth are on the cog. When you click on a cog the chain moves and all the highlights in GearCalcs tables and in the data entry area also move to show the currently selected gear. Clicking on the tables or cog teeth value boxes will cause the gearing diagram to change, showing you visually which gear this is and saving you having to scan down a table in order to find the correct row showing the calculated values for the selected combination of gears.

The diagram is not drawn to scale. (But the diagrams in CrankCalc and WheelCalc are!) To save space and to ensure that the cogs are a minimum of 3 pixels wide (so that you can click on them!) the chain wheel appears proportionally smaller and closer to the cassette than reality. This is actually a big advantage because it exaggerates the chain angles making it easier for novices to see why one combination of cogs is preferred over another combination that would produce a similar gear ratio. Accurate chain angle values and offset distances are calculated however and these can also optionally be displayed in GearCalcs main window and in the chain alignment window. There isn't any need to worry about the actual numbers for chain angle though the only thing of importance here is bigger or smaller.

Gearing Alignment Diagram

Gearing diagram: Click cogs to see the chain alignment window Click freewheel to see the gear alignment window Click chainring to see the gear alignment window

The gearing diagram in the gear calculators chain alignment window (left) is similar to the one above. The difference is the line joining the chainring and freewheel cogs is thinner and allways vertical. This is because it represents a pair of cogs where one is exactly in front of another which would give a chain angle of zero degrees (maximum efficiency). When you click on these cogs the chain ring moves sideways to show the new alignment.

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Designed by Nigel Jones