I've got a 2x9 setup on my bike, and use two chains, rotating them whenever I remember.
Both chains are now showing around 0.75% wear according to my chain measuring tool - this one http://www.chainreactioncycles.com/Models.aspx?ModelID=10219
If you drop it on the chain, it won't go in, but give it a shove and it clicks into place on the 0.75% side. So presumably that means my chains are near enough 0.75% worn...
Now, do I go and buy two more chains, and run those down to .75% wear and keep on buying new chains when I get to 0.75% wear and thereby get an eternity out of my cassette and rings?
Or do I just run those two chains into the ground, taking the rings and cassette with them? That way you end up lashing out a fair old whack on chains, rings and cassette at once, but everything is worn together?
Or do I need to swap the lot for new anyway to avoid chin / bar interface?
