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My bike's chain broke, so I have to replace it now. The question is - how can I tell what size chain do I need to buy so it fits the bike? It's a 5 gear internal-hub bike.

  • You mean "length" not size. Do consider using the site's search functionality before firing off questions. Also, do read the Tour in the Help menu to get a better idea of how stackexchange works - y.ou don't have the badge for reading the tour, so we know you haven't. – Criggie Apr 14 '16 at 0:17
  • @Criggie - Length isn't very critical, since virtually all chains come with extra links. It's basically the width of the chain that is the issue. – Daniel R Hicks Apr 14 '16 at 1:33
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Modern chains all have 1/2" pitch (distance between rollers), but there are several different widths. 1/8" is common for single speed and internal gear hubs, while 3/32" (and narrower in the case of are common for derailleur-based bicycles) though many single speed/internal gear hubs use a 3/32" chain (this depends on which cog+chainring combo is used).

You should check the cog+chainring for a marking of 1/8" or 3/32", and if it has one or the other, pick up a single speed or 8 speed chain respectively. Alternatively, take your old chain and a pair of calipers and measure the inside width between the plates of the chain and see what it comes out to. If theres a quick link in the chain, you can also note that 1/8" quick links have both pins on one plate whereas 3/32" chains have one pin on each plate.

If you take your chain to your local bike shop, they'll be able to sort you out quite quickly. Note not all chain tools can break 1/8" chains.

Once you've acquired the appropriate chain, you simply need to find the length of it, which will depend on if you're using a chain tensioning pulley or horizontal dropouts (the chain shouldn't be too loose or too tight, but the dropout gives you some wiggle room for length with this). You can also do this by just comparing number of links with your old chain as well.

  • Yes, when matching old chain length to new it's important to count links, not simply measure overall length. The old chain will have "stretched" at least one full link in length, probably. – Daniel R Hicks Apr 14 '16 at 1:34
  • How does this improve on the answers to the duplicate question? – Móż Apr 14 '16 at 2:05
  • @BlamBlamBlam - Unlike the alleged duplicate, my answer is correct. For example, none of the answers explicitly note that 1/8" and 3/32" cogs are common on single speed/IGH hubs. There is no note on the differences in master links to help identify chain width in those answers either. – Batman Apr 14 '16 at 2:21
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    alleged? It seems like the same question, which means you should answer the original so that this can be deleted as a dupe. – Móż Apr 14 '16 at 3:50

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