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Old 08-17-14 | 09:58 PM
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lasauge
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Joined: Jun 2011
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From: Newbury Park, CA
AFAIK "compact" chainrings are a modern concept, since you really need a freehub mechanism that can take a 12 or 11t smallest cog to benefit (on a roadbike anyways), and that excludes any bike with a freewheel. However, you can make almost any crankset "compact" by installing smaller chainrings, assuming the BCD is small enough, see the column labeled "smallest ring" on this chart from the Sheldon Brown site:
Sheldon Brown's Bicycle Crank/Chainring Bolt Circle Diameter Crib Sheet

For an example, consider my '83 Stumpjumper with a Sugino AT crank (110bcd) that's set up as a compact double (48-38 rings). I'm using this crankset this way because I don't really need the very small gear of a triple crank, and this lets me use a narrower BB spindle.
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