This afternoon, while dressing the tires on my wife's Toyota Sienna, I noticed that two of them have a slight bulge that, in both cases, runs from the rim almost to the tread. On the front left, it is about an inch-an-a-half wide and maybe an eighth high. On the rear left, its smaller, maybe a half inch wide and a sixteenth high. I have never seen this before. Is it a blowout waiting to happen? Does she need to replace the tires; if so, how urgently? They both have about 5/16" of an inch of tread left.

 

From what I've read/heard, a bulge or bubble in the sidewall indicates internal structural damage, with the air pressure pushing the rubber out more at that weak point. The bulge could be due to a flaw in the tire build, or, perhaps more likely, to a heavy road impact such a hitting a pothole at speed. Either way, tire replacement is advised, as the tire is more susceptible to sudden blowout.

A 5/16" (10/32") tread depth sounds like fairly new tires, so maybe you could get some relief through the tire's warranty.

 

Thanks. I hadn't thought about the impact. That would kind of explain it being on both tires and worse in front.

 

I would have them inspected wherever you bought them. They should be willing to come out to the car and check them out for free and let you know what they think. If you do not get a satisfactory response then go to the manufacturer directly, with pics. It will just cost you your time. Either way I would not drive them much or for long, or at all if possible.