Originally Posted by
Randy Cox
Any idea why it would just snap--on both sides simultaneously?
Pushing against the seat back while pedaling put upward bending forces on both ends of the "U" shaped tube that broke off. The fault lays in negligent design - the "U" shaped tube needs to be braced to prevent bending, or angled downward slightly to reduce bending forces on the joints that broke.
Originally Posted by
Randy Cox
Also, I hang my backpack (with a laptop computer and other stuff) on the back for my commute to and from work. Could that have been what "put it over the edge"?
No. The added weight is supported by the struts and puts no significant stresses on the joints that fractured.
{EDIT} Correction; After looking at a side view, if you mount your load (laptop, stuff, etc) on the upper most, horizontal member (not the lower, horizontal member that broke (and shown in your image)), then yes, the added weight will increase the bending forces on the member that broke. However, mounting your load on the lower, 'broken' member (after the repair or replacement, of course) and you'll be fine because the load will then be primarily supported by the struts (aka, seat back braces) and not the seat back.
Question: Is this an EZ-1? And do you have the seat adjusted all the way aft?