My bike chain has been "skipping", so I've gone through the obvious:
- I replaced the chain
- I replaced the smallest cassette cog, which was showing significant wear
After my replacements I noticed what the real problem was. Every once in a while, rather than the chain being pulled into the valeys of the rear cog, a chain link land on the tooth, and will not roll into the cog's valley and engage. Each subsequent link of the chain will land on a tooth. When the last engaged link begins to leave the valley, all the disengaged links will be snapped back into engagement by the rear derailleur.
What's going on here? Is my rear derailleur's tensioner spring just too old?