i used to get those bubbles on my side wall all the time. I have 3 tires that are almost brand new in my backyard right now that have bubbles. It always happened on the passenger side. It's from rubbing up against a curb. Once i was made aware of that , i avoided rubbing up against things & i haven't had a bubble since. I don't think it's a defect in the tire. I think it's cuzu probably rubbed upagainst a curb while parking. My little curb was on my driveway. I now back out of my driveway and i don't get them anymore.