Originally Posted by
eduskator
I'd say 9 or 3 o'clock. I don't believe there is an official recommended position but I want to avoid sealant building up and drying around the valve. I store it with the valve down as well.
I find the last part of your post amazing. I've had the reverse experience. When I store my bike with the stem in the 6 o'clock position, both the front and rear wheels empty by morning-- totally empty. when I leave the bike stored with the stems at 12 o'clock, they hold the pressure the best.