Some 1/8 chains and chainrings are sold as "1/2 1/8" and some as "1 1/8". What is the first number describing?

My understanding is that practically all modern chains have a 1/2 inch pitch.

  • I think the reason for 1/2 inch vs 1 inch is that some manufacturers measure the distance pin to pin, while others measure the length of and entire link which includes the inner and outer plates, and consists of the distance between 2 sets of pins. – Kibbee Jun 19 '15 at 18:24

There are two measurements, given as pitch x width. The pitch is the distance between rollers and width is the width that the sprockets have to fit through. The pitch is generally 1/2" on modern chains, but some old bicycles (esp. old track bicycles) use 1" pitch chains (skip link or block chains).

The width changes depending on number of speeds (so you'll have a lower width for higher number of speeds). So single speeds will often use 1/8" (some have sprockets designed for 3/32" though, so you should check), 8 speed will use 3/32" , higher number of speeds will use 11/128" (11 speed), etc. [possibly different between manufacturers].

  • BTW. It's been 3 years since 2018 and I still cannot find a picture of a 1" chain. – tymtam Oct 1 '18 at 23:58

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