Originally Posted by baxtefer
I'm an engineer and a physicist.
by slack i mean 1/2-1/4" of vertical play.
tight chains like seely described (i.e. no vertical free play) are a recipe for destroyed bearings and worn chains and cogs
I have that much play in my chain when actually depressing it, but I have no free play in my chain at all. The idea is to get just enough tension that it is impossible to throw the chain over a cog or chainring tooth, thus eliminating the possibility of losing your chain.
When people come into my shop and suggest a looser chain, they generally have a significant sag in their driveline. I cringe when I think about them having to take an emergency U-turn or hockey stop. It's all about safety.