1.) This is a 1989 Cannondale SM2000, is that a good derailleur?

2.) Will these dropouts suffice for a coaster brake? What if I over-shorten the chain? Do-able?

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  • That's not how a QR lever should point.
    – Batman
    Jun 1 '15 at 21:46

A derailleur (or pulley-type chain tensioner) can't be used with coaster brakes. You also have vertical dropouts, so if you want to run something without a derailleur, you need an eccentric hub (which I don't think exists with a coaster brake -- the only one I'm aware of is the White Industries Eno) or eccentric bottom bracket (Phil Wood makes some). You can't just shorten the chain. You'll also need a new wheel on top of that (or at least a new hub) so that you can have a coaster brake. All in all, putting a coaster brake on a bike like this is not a good idea.

As for the bike being any good as is, that's in the eye of the beholder; it looks like it was a decent bike when it came out, so assuming everything is in working order it'd make a great commuter, for example.

If you really want a coaster brake, sell the bike and get a frame with horizontal dropouts.

  • Despite that being the answer I was dreading, thank you so much for your advice. Hand brakes it is. The bike's components work splendidly, it's just that I saw a video of klunking online and one thing led to another.
    – Ben
    Jun 1 '15 at 20:57
  • There is one thing you can try. It's a bit crazy, but you can try to find a perfect combination of back cog, front cog and chain size so that the chain is ok when the wheel is a little away from the dropout. Then, push it back and close the skewer and voila. You're playing with very small tolerances, so you need to be lucky, but my brother runs his bike like this and I see him happy cycling all the time with his coaster :)
    – super
    Jun 3 '15 at 4:27
  • Magic ratio lets you run single speed without a tensioner. eehouse.org/fixin/formfmu.php. It's a calculation factoring chainring size, cog size, and chainstay length.
    – jqning
    Jun 3 '15 at 4:41
  • People do it, but its not a good idea. You'll need to faff with half links and other screwery. And its not like frames with horizontal dropouts are expensive these days -- they'll be pennies next to the amount you're spending for a rear wheel with a coaster brake.
    – Batman
    Jun 3 '15 at 13:53

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