Get some wrap around cycling glasses, your eyes are watering, from the cold, dry air that is hitting them as you ride. The lacrimal-nasal duct is channeling all the excess tears, from your eyes, down through the duct, and into your nasal passages. This is what causes that runny nose, if its all clear fluids.
All bets are off if you have either a cold, or any URI, and you are getting ugly stuff in the discharge. (Let the strange replies about this begin, keep it a little civil please.)
Bill
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Semper Fi, USMC, 1975-1977
I Can Do All Things Through Him, Who Gives Me Strength. Philippians 4:13