I got a pair of these last year. First off let me say that the material quality is great compared to any other bibs or shorts I've had. I little too good as they don't give much.
I'm 5'7" and 145 on a good day. I typically wear a medium and in some American brands occasionally a small. That said I thought these would be fine in that size. Not true. In width and girth they were great but it is like they were built for someone 4 inches shorter than me and I'll give you one guess where all that pressure comes to a crux. You know what I said about great material? That also means they didn't really ever stretch out or "break in." I really feel severely mashed and bruised in my bits and pieces after a couple days in these bibs.
Great quality but do yourself a favor, order 2 pair and try them on or go at least a full size up.