Which derailleur should I use with a Shimano 7 speed freewheel 14-34T megarange? Which derailleur should I use with a Shimano 7 speed freewheel 14-34T megarange in order to prevent the derailleur from rubbing the cassette in 2nd.
This one. 



Or this one. Or any 7 or 8 speed Mega Range rear derailleur from Shimano.



This issue can also be an adjustment of the B tension screw on your existing derailleur.