I needed to change the tube as a consequence of a flat tire and I am in the situation that it's just impossible to put the tire back on the rim.
In almost ten years of experience with road bikes and MTB, I never experienced this.
I tried to use any possible tips, for example from the question How to get the tyre back on to the rim easily?
Every time I try, I end up pinching the tube and it's just impossible to put the tire in. How can I fix this?
I am hypothesizing crazy things, like: dilatation of the rim, need of industrial tools, ...
Edit (to address Neil's question): the troubles are given by a 700x23c tire on a 700C rim of a fixed gear.