Now that I'm able to ride a fair distance without stopping (yea!), I have an issue. After 10-15 minutes of constant riding, my feet slowly go numb. Somewhere around the 20-25 minute mark, my feet (and only my feet) are totally numb. Nothing I do on the bike seems to help (e.g., changing positions on saddle; leaning over more or less; standing up on pedals; changing foot position on pedal). When I get off the bike, the feeling comes back quickly.
I'm riding a Surly Trucker, Brooks B67 saddle, large platform pedals, with running-type athletic shoes (tied pretty loose).
Any ideas why this is happening?