Only 1/8" Or old C&V roller chains that went out with 6 speed freewheels..
a derailleur chain now has flush pins, so shortening is a one way operation..
To lengthen a chain you need more quick links and an extra section of the same chain..
the act of pushing the chain making machine rivet set pin stretches the link hole it was riveted into..
so, simply pushing it, the pin, back in will after that, not be secure.
....
Last edited by fietsbob; 09-16-17 at 09:06 AM.