I dusted off an old steel frame french road bike (circa 1980) and have been enjoying the summer riding so far. Unfortunately I managed to snap the chain on it. No big deal, put a measuring caliper on it and read off 1/2" pitch and 3/32" width. Went to the local bike shop and picked up a cheapo SRAM chain and put her on.

Now the chain skips every 2-3 revolutions. It turns out the pitch isn't 3/32" but slightly smaller, causing the chain to slip. This leads me to think that the old french chains are a non-standard size. Or has the original chain stretched over the years? Is there any way of finding a replacment chain for it or do I need to update the chainring/cassette for something more modern and compatible? Seems a shame to do away with the original parts.

Anyone out there have experience of doing up old french bikes and may have some knowledge?

  • "It turns out the pitch isn't 3/32"... " - how do you mean? a) possible typo and b) pitch of what? – Swifty May 20 '20 at 20:02
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    It's possible that the chain is the right size but that the rear cogs and/or chainrings have worn down to a point where they no longer work with a chain that isn't stretched – Kibbee May 20 '20 at 20:09
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    Although French bikes often have weird French-only specifications (for handlebar clamp diameter, bottom bracket threading, etc), the chain is one part where they are in line with common practice. @Kibbee's probably got it. – Adam Rice May 20 '20 at 20:20

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