The rear gear cable on my bike snapped while I was biking on it today. Luckily I had a replacement cable with me, so I thought I could replace it right away. But it turned out that the cable head inside the gear shifter was jammed, and impossible to get access to and remove.
The mechanical parts on my Trek 4100 mountainbike were getting old and worn out, so I replaced the bottom bracket, front chainwheel, multiple freewheel, rear derailleur and bike chain.
It isn't that difficult, and the process is a lot of fun! On top of that you save a lot of money, in stead of letting your bicycle repair shop do it.
