I have had a Timbuk2 filled to the brim, both on motorcycle and bicycle, works excellent. I use a commute to carry my laptop on motorcycle, haven't tried it on the bicycle, but that bag has been back and forth to Europe 3 times for extended trips and still going strong. The company has off shored its production of there more fashionable bags, but I believe the core messenger bag is still made in SF.

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That being said I have eye balling Chrome bags lately as a replacement for my messenger bag, they look like they are more stable, and I like the quick on and off buckle.