Originally Posted by
Bianchigirll
I would say unless the cracks occour in the first 100 or so miles it is most likely normal wear and tear. unfortunatly not all of ride on glass smooth roads all the time and there are just too many variables to say it is a defect.
No.
Hitting a pot-hole or jumping off a curb makes for a significant tension decrease in the bottom few spokes with negligible changes elsewhere in the rim.
While you might put a flat spot on the rim or even cause it to collapse if you get a big enough hit with side loading, you're not going to cause failures like the one illustrated.
Spoke breakage and rim-bed cracks come from fatigue, where the number of cycles which can be survived depends on average stress, magnitude of the stress cycles, and the materials/construction.
Where the rim is failing like that spoke tension is too high, there isn't enough material in the spoke bed, or there are material problems. Those are all defects whether they show physical effects in the first 100 miles, 1000 miles, or 10,000 miles although getting a warranty replacement may be difficult in the later cases.
Properly designed rims last until you wear out the braking surfaces or damage them in crashes.