Rainy days - front, brim down.
Sunny days, training, easy days, no sprints (not even giving into temptation) - front, brim down. You can't see for sh*t with the brim down without craning your head unnaturally upwards.
Sunny days, sprints, temptation is a possibility
or
Racing - I wear a "modified" cap - one with the brim cut out. Do this after you accidentally dry a cap and ruin the brim. Cut the threads holding the brim on. Works great.
Optional cap treatments:
- V-cuts for ventilation
- cut top of cap off (think golf or accounting cap)
All credit goes to my ex-pro friend. He showed me all of these tricks.
cdr