My bike's 18-year-old rear brake cable finally gave in and snapped the other day. Luckily there are dozens of abandoned bikes around campus with nearly all of their parts stripped, and the one thing left on most of them is the brakes. (By the way, it's not exactly frowned upon here. When a bike loses its wheels, the rest of the parts are pretty much fair game unless the owner comes forward and complains. People occasionally drop out without unlocking their bikes, just leaving them to rot and take up space, so whether or not it's illegal or against school rules or whatever, nobody cares) Anyway, my question to you is... Am I better off replacing just the cable or the whole brake system? I'm hesitant to try a new cable, because when I reattached mine it was only about 1/3 of an inch shorter, but that made all the difference and the brakes were pretty much still unusable.

Oh, and don't just tell me to get a new bike. That's likely what I'll do, but I have an abundance of free parts and this is a bit related to my mechanical engineering major, so you know. I have to at least try it a couple times.