A case of the wobblies

I just bought an old (maybe too old) Peugeot and I am experiencing a problem when I pedal. The horizontal shaft that the two pedal assemblies are mounted to feels loose or wobbly. It's not a firm, solid, smooth revolution, but a floppy one.

I tried to tighten the bolt, but it didn't help much. Is there anything I can do—or did I "get the shaft," so to speak?

—Non-union but Wobbly nonetheless

Cut it out, Wobbly; bad puns and oblique references are the sole prerogative of the blog author. Didn't you read the fine print on the user agreement?

You didn't necessarily get the shaft; this is a pretty common deal on older bikes. Yours probably is old enough to have cottered cranks—the kind where a small, wedged bolt pierces the width of the crankarm and has a nut on one side ( like this). If so, the problem is probably that the nuts loosened years ago and the wedge parts of the cotters have worn down over time, allowing things to get sloppy. The solution would be to replace the cotters. Good news: cotters are cheap. Bad news: A special tool is needed to do it right. It's probably best to have a shop do it and charge you the twenty bucks or so.

There's a chance the problem could be in the bottom bracket—the bearings inside the frame, where the crankarms attach. If so, adjusting the cup and lockring on the left side of the frame might solve it. (Again, alas, special tools are needed to do it right—but it's a smaller labor charge than replacing cotters.)

It's also possible—but less likely—that the bearings inside are toast and need to be replaced (bigger labor charge). This could get tricky because your bike likely is old enough to have French-threaded bearing cups, which can be hard to find (but not necessarily expensive).

For some comfort in all this, create an account on eBay and then browse the "completed listings" to see how much collectors are paying for certain old Peugeots.