Friday, in the daylight, before leaving to go do errands, I looked at my tires again. Holy Cow! My driver's side front tire had a huge pre-blowout bulgy spot on it (on the sidewall of the tire). I can't imagine why it didn't blow out on the Interstate while I was driving--doing 65+ barrelling down the highway in the dark at midnight. So scary. If it had blown who knows if I would've been able to keep the car under control. Pretty much scared me to death. I snapped a cell phone picture of it:
The tire still had fairly good tread and wasn't all that old (but it was beyond the warranty period). I guess I was lucky that this was visible on the outside sidewall, and not located on the inside sidewall.
Be careful out there.