Joined: Jun 2011
Posts: 1,180
Likes: 0
From: Sunnyvale, California
Bikes: Bridgestone RB-1, 600, T700, MB-6 w/ Dirt Drops, MB-Zip, Bianchi Limited, Nashbar Hounder
Looks like tube getting caught between rim and tire bead near the valve, or you have a deep center channel in your rims near the valve hole this is unsupported by the rim strip you're using.