Nothing has been added to the bikes with the exception of different seats and tires :/ so i doubt its anything i directly did to the bike. One possibilty that i was thinking about was that the weld temperatures might have gotten a bit high since the bead is all over the cups. I really have no idea how long we rode on the bikes with them cracked like that. My riding style to hers is much different. I bunny hop the bike all over the place, ride wheelies on it. Im definatly much more agressive on my bike (small size, hers is the medium) than she has ever been on hers.