Originally Posted by orcanova
you need a long cage deurailler for a triple crank...
He's using a chainring from a triple crank on a double, not a triple crank on a double crank setup.
OP: The 50T chainring could be worn, compare the teeth to your old chainring. If they're narrower (more like a shark fin) that's a good sign of wear which would cause the noise your describing.