The frame size listed for each bike is recommended. You may choose to use a wider frame than listed for a particular bike if you intend to go to a larger bike in the future, but the wider frame will look wide on the bike that is intended for the narrower frame.
Bikes that have two size frames listed would choose which frame to use according to whether you have side tour bags on the bike.
† Stock motorcycle in good condition may have ground clearance lower that 3″ with main attachment brackets installed.
Voyager Trike Kit Information
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