Originally Posted by
RubeRad
General question: anybody have any tips on how to diagnose and address shifting/derailleur problems that happen only under load, and can't be observed simply by turning the cranks when the bike is in the stand?
Specific symptoms: Cogs 4-10 (big/slow) are shifting smooth, riding smooth under load, no noise. Cogs 1-3 are shifting fine, ride ok under light pressure but when I push, there is either slipping teeth or spurious failed shifts (I can't tell which while riding, and can't see it in the stand) all the damn time.
Relevant details: Krampus 1x10, 11-50 11-42. Deore XT. Problem appeared suddenly after chain broke and was replaced by a new chain. The old chain was VERY worn (stretched).
Obvious solution: just replace the cassette you dumb cheap bastard!
That is the classic symptom of running a new chain on worn sprockets.
Secondary general question: why is it that I am experiencing problems only in the small cogs? […] Is there something about how load is spread onto fewer teeth that makes smaller cogs wear faster?
Yes, smaller tooth count sprockets concentrate the wear onto fewer teeth, so they wear faster than the larger tooth count sprockets.