There are too many of us here to wave to everyone. I do say "nice bike" or whatever if I see someone with a particularly cool bike. When I lived in California, most motorcyclists waved to each other, but on the east coast it seems less common.
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1964 JRJ (Bob Jackson), 1973 Wes Mason, 1974 Raleigh Gran Sport, 1986 Schwinn High Sierra, 2000ish Colian (Colin Laing), 2011 Dick Chafe, 2013 Velo Orange Pass Hunter