Easy to explain what happened: the structure has no diagonals. You could avoid collapsing by fixing this rack to the wall. A typical garage wall has 2x4's inside, you can easily find these and attach the upper bar of the rack where 2x4's are.
Uh....I live in Belgium..you would be hard pressed to find a house made out of wood...aint no 2x4's in the walls of my garage.
Diagonals-shmiagonals, The damn plastic cross-member broke at the corner where one of the vertical tubes slid into it. The actual tubes were not folded/broken except slightly bent where they connected to the cross members due to the the rack falling over when the cross-member cracked/broke.
I was standing in front of it measuring the length of my backplate for a discussion with another SB member when the rack collapsed.,,,the rack was overloaded and inherently unstable standing in the middle of the garage, Totally my fault....just looking for something to replace it with now.
-Z