585 pound "new girl" sat on a 30 inch ring. Not really a popping session, but it was there, so she sat on it. It held her, which isn't the expected result but isn't surprising, either, provided she spreads her weight over the whole thing. She shrugs, carries on with conversation. After a minute I can't stand not knowing, so I ask her if it has deflated, and she says it hasn't. She scoots forward to feel it behind her, which unevenly loads it...and it still doesn't pop. Some of her weight is on the floor, because she doesn't fit on the ring, but there's still a crapload of weight on it, and it's unevenly loaded. I look behind her, and there's a huge bulge in the vinyl. It looks like a bubble about to burst!
She got off it and we looked at it. One side is stretched more than I've ever seen. We add air so the thing is tight, and I grab a tape measure. One side is 23 inches around and the other is 30. A new record, and it doesn't even have any weight on it. It might be permanently stretched.
We put it on the floor and she rolls onto one hip, pushes the ring under her, and leans on the thing, on the small side. It holds her, so she leans into harder. It expands noticeably. She rolls off so I can get the measuring tape around it, and rolls back onto it, harder than before. 33 inches, and the tape gets tight immediately, so it's stretching quickly. I release it, she rolls more weight onto it, and I measure again. 34 inches, and it gets tight again. I release it and measure again. 34 1/2 inches. She's afraid it's going to blow, and I admit I'd like to keep it and see if it recovers, so she rolls off. We add air so it's tight again. It's 34 inches unloaded but full. I may have mis-measured its largest size, because it seems to have shrunk quite a bit...to 34 inches.
After a while it feels really tight, unloaded, and I know it will just develop a leak if I leave it like that, so I let some air out. It's now been quite a while more, and it is now 22 1/2 inches on the small side and 32 1/2 inches on the bulging side.
Both sides of the seam are bulged, top and bottom, but it's bulged on one side, the warning label side, much more than the other side, and the label is seriously distorted. And you know how the outside of the ring normally puckers even when it's full? On the bulging side of the ring it doesn't pucker. And the hole isn't round.
She weighs just about as much as I do, and I've sat on these things many times and never seen this.
ETA I let more air out so it can recover some more, and hours later it is now a little bit soft and 22 1/4 inches around the small side and 31 1/2 inches around the bulging side.
ETA We loaded this thing up again and got it to 37 1/2 inches. I then let it sit for days and it recovered, inflated but not overinflated, to 34 inches. My partner popped it with just part of her weight.