[jakeru]

Sorry I don't know what the adhesive is exactly, but I can add that I've had one fall off after I washed the car and it froze the following night. The next day, I may have been buffing out some sealant on the wheel after, and the crest fell right off when a I touched it. It was definitely on there securely before it froze, but not after.

My theory is that some water from washing the car had remained behind the crest, and when it froze, it expanded and pushed away the crest far enough that it separated the adhesive.

The factory adhesive is thick (maybe 1/16"-1/8" thick squiggly-shaped bead), gummy-like adhesive that I think apparently lost its flexibility due to old age. Thickness and flexibility is good here to make the flexible center cap easier to remove. (It aids removal and reinstalation to have it not be so stiff.). Super glue would be a bad idea. I would think epoxy would work OK, at least it would be thick and strong, but something more flexible like maybe some silicone or polyurethane sealant-type adhesive may be best. Maybe something like Polyurethane window-weld.