Originally Posted by
cderalow
This is assuming that the derailleur limits are adjusted with the cable being slack or not attached and that it's allowed to rest on the stops (the correct way to setup a derailleur)
If the cable is attached to the derailleur and then the limit screws are adjusted, the derailleur won't be resting on the stops.
case in point, OP adjusted low limit and now cable tension has clearly changed. thus, it wasn't resting on the limit stop.
OP should have an inline barrel adjuster on the cable somewhere (at the shifter) that should help him trim the noise out.
the better question should be: why did the OP feel the limit needed to be adjusted to allow more movement inward.
The OP backed out the low limit screw because he was having difficulty shifting from the middle to low.