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I have a 60 year old bike that is eight speed (2 chainrings, 4 cogs in the back). The smallest gear on freewheel is worn out, visibly hooked. I've found a replacement freewheel.

I don't have experience with bikes this old, but I've been riding since the eighties. My experience has always been that chains wear out before freewheel sprockets, but I've checked my (original, I believe) chain at several points with my Park chain checker tool and it's below .75 everywhere. Do you think I can continue running this chain on my new freewheel? I would like to keep it as original as possible and finding a "period correct" chain would be very difficult.

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  • Can you add a photo of the chain area of the bike ? Also, measure the inside and outside widths using calipers, that will help to know if a 6/7/8 speed chain will work or if you have to source something special.
    – Criggie
    Oct 28, 2021 at 3:39
  • Do you intend on riding this vintage bike ?
    – Criggie
    Oct 28, 2021 at 3:39
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    I do plan on riding the bike. It uses a 3/32" chain that measures .330" wide at the pins.
    – Eric
    Oct 28, 2021 at 13:39

2 Answers 2

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For something like this, a ruler is the superior way to measure chain wear. The reasons are kind of complicated, but essentially most modern chain checkers are only reasonably accurate by virtue of roller thickness being more standardized than it necessarily has to be or would be on an old specimen. A ruler requires squinting but will not lie. The Sheldon approach of replacing if wear is greater than 1/16" over 12" is good.

I understand that some 4-speed freewheels use 1/8" chain. I have no idea what the approach to replacing that chain would be other than try some current ones and see if it works. If yours takes 3/32" and measures about 5.5mm cog to cog, or a little more, then I don't think there's any issue using a 5/6-speed chain, which you can find good quality ones of still made that basically have vintage looks (Izumi).

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    I just checked and it's less than 1/16" over 12" in length. I read that approach for measuring chain stretch in the Tom Dougherty book back in the eighties, but haven't used it since I got my chain checker tool.
    – Eric
    Oct 28, 2021 at 13:44
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Chains are consumables and will wear over time. Presumably this bike is to use, not as a static showpiece?

If you value the current chain for period correctness, take it off now before it wears out, and fit a suitable replacement - a 5 speed chain might be okay, otherwise a 6/7/8 speed chain might be the nearest you can find.

Clean, lube, and bag the original chain for storage, and only fit it to the bike for a show or special event.

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    I'll see if I can find a good five speed chain.
    – Eric
    Oct 28, 2021 at 13:45

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