this is what it looked like when i tried installing marathon pluses on my velocity rims:


Schwalbe seems to manufacture their tires a bit larger in diameter than most tires. Velocity may make their rims a bit smaller as well. The combination is deadly.

I would guess that it is a similar situation. The bead is working its way off of the rim and the tube is blowing.

For me the solution was to get some Bontrager hardcases.