Longish tire story(s) and a question
Yes I have experienced tire defects, but not with my BMWs. Many years ago I had one in a set of Falkens (don't remember the model) on a Porsche I owned. After rotating the wheels I began to think that one of my ball joints was failing. You could really feel a vibration in the front end at certain speeds. It was suggested that I have the wheels rebalanced. Only one required it and after rebalancing with considerable weight the wheel still proved problematic on the front of the car. As it turned out the tire was both out of round and a little lopsided. I replaced it and the problem was resolved.
Fast forward to a couple months ago when I purchased tires for my JEEP, BF Goodrich All terrain TA KOs in 31x 10.5. When i went to pay the clerk notified me that one of my wheels was severely bent and proved very difficult to balance. "Nothing doing" I said as the wheels are beefy alloys in perfect condition. They showed me the wheel on the car and I'll bet you there was a pound of wheel weights on it! I suggested that the tire was defective. They (Costco) disagreed, saying first that it was "impossible", "never happens", "never seen it before in all their experience", "quality control too tight", "lots of SUVs with bent wheels", bla, bla, bla...... I insisted and argued further that performance and safety could be compromised. They countered that yes it could, and that is why I would have to sign a release before they gave me the car back. "Ridiculous", I said, "give me another tire". They resisted. "Okay then swap out the wheel with the one on my full size spare. If you can't balance that one you have to admit that it is the tire". I also noted that their life could be made easier by just putting a new tire on the questionable rim and if it balanced up okay it had to be the tire. Noooooooooo, they insisted on changing out both the spare and the other wheel saying rather smugly that if my wheel was the problem I would have to pay for two additional mounting and balancing charges. I said fine and why not make it interesting? I'll bet you $100 that it is the tire. Well they wouldn't take the bet, and yes in the end it was the tire.
Bottom line there are defective tires and it can be up to the buyer to do the ultimate quality control. I'd be interested to know what the industry considers to be the maximum allowable weight for proper balance before a tire is considered defective.