>>1721710based and 1970s pilled, also the correct term
its effects are chain wrap and chain aliment
from time to time I call it the B pulley due to its proximity to the B pivot
Tension pully does not normally effect shifting or chain aliment unless something else is seriously wrong
>>1721713>problems that may be attributable to the shifter insteadsuper unlikely but maybe the shifters index points do not work with the parallelogram curve of that derailleur
or the spacing of the Sprockets does not match the index points
but worn out pivot points along with pulley float make this kind of problem harder to identify (hit bump, bike changes gear)
have apply occams razor and start with the least complex thing that could be causing a problem
cable tension too low or too high
pivot points bound up with gunk
parallelogram spring worn out so that although the derailleur may shift down there is nothing strongly forcing it to do so
