I had a massively frustrating experience on my bike a couple of days ago. I burst my rear tube. I went and purchased a new one. I had the tools necessary to replace it on the fly but I couldn't get my rear rim out of my bike. It was like whoever last installed it shoved it in incorrectly and I just didn't have the leverage (or skill?) to get it out. I'm not a bike mechanic, but I like to think I can figure things out, and I try to work on my own stuff as much as possible.