Great question. As a bottom, I've often wondered the same. I do know that if I'm getting butt fucked frequently with a long and thick one (8", 20cm) I can work that cock to the point where it doesn't hurt so he can just bang away all he wants. But, for instance, I hadn't had any anal sex with a hung guy for 4 months, and last week, I did and it really hurt when he went in deep. He was fucking me doggy style and It hurt to the point I was yelping and jerking forward when he plunged in deep, so ya, he knew when he was hitting that second ring,
But, could he feel it? That is the question.
Tops.... Please answer this as I'm sure that there are a lot of bottoms out there like me that would like to know.