Originally Posted by edgewant
Last fall after returning from a trip a sidewall defect on one my tires grew by about 100% after 180 miles. I dismounted the tire/wheel assembly and took it to TCI in Nashville TN to see if they could get Michelin to warranty it. The tire was only 2-1/2 years old and was mounted by Freightliner when I had the tire and front airbag upgrade.
Michelin's determination was that the tire was either damaged during installation or suffered impact damage and was not a manufacturing defect. As shown in the attached picture there was no wheel damage, so I seriously doubt there was impact damage.
Very disappointed in Michelin.
Edgewant, what you have in the picture is many times what we in the tire business refer to as pinch shock or rim pinch. It's not just Michelin who will not adjust tires with this condition, since it is considered a road hazard. Every brand of tire we sell, either passenger or commercial have a disclaimer for pinch shock.
It can be caused by several things, a few of which are potholes and curbs. Many people drive up over curbs when pulling in parking lots, etc.
The progressive problem is that the bulge may not occur till awhile later, well after the impact that caused the break.
EDIT after rereading OP: When they dismounted your tire, they most likely were able to find a little tear in the inner liner. That's the first thing that the adjusters look for.
Here is some reading material on this occurrence, as well as Michelins service manual.
Michelin Demo - Truck Tire Service Manual
There is a pretty good video on the TIA site about pinch shock, but I haven't figured out how to share it since it's a member only site that would require my password. Let me do some looking around and see if I can find something similar.
EDIT 2: Here is a youtube video that helps explain a rim pinch. I've seen it happen several times on the larger stuff, when going up over curbs.