In all my years of working on bikes, this is a first. Bought a new 9 speed KMC chain and 9 speed cassette to replace a worn 9 speed drivetrain recently (single chain ring). Went to put everything on tonight, except the new chain is way too short -- even on the smallest cog the derailleur is so stretched I'm afraid turning the cranks will rip it off the hanger.
Comparing the new chain to the old chain (also a 9 speed chain, in case it isn't clear) shows that the new chain is about six inches shorter. I don't know how many links are in the old chain, but the new chain supposedly has 116 links and the highest link chain I can find on the internet is 120. I've never had so much difficulty overhauling a 9 speed drivetrain before.
Can anyone explain what the hell is going on here? I've got pictures on my phone I can include if the description doesn't make sense.