Best bag for a bike commute?

What is the best bag to get for commuting by bike? My commute is about 1 hour each way on bike and my bag is pretty heavy. My current back pack really pulls down on my shoulders and makes them very sore. It doesn't have a belly strap though. I want to buy a Timbuk2 because i need a more waterproof bag so i can ride in the rain. I was wondering if you thought a messenger would be more comfy for bike riding than a standard back pack. Thanks.
Inappropriate?
1 person has this question

User_default_medium