Originally Posted by
dougmc
It's a well-understood heads-up to all around you that you're going to do something -- turn, change lanes, etc.
A more reliable indicator of an action that is about to happen is an arm signal - I make sure to signal before a lane change or turn. A headcheck communicates nothing in particular.
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Bacchetta Giro A20, RANS V-Rex, RANS Screamer