Worn jockey wheels are often overlooked during annual maintenance. To ensure your drivetrain is operating smoothly, replace your derailleur's jockey wheels when they look worn.
For 2008 and newer 9 or 10-speed non-Type 2 XO derailleurs, purchase 'Suit 2008-2011'
For 10 speed Type 2 XO derailleurs, purchase 'Suit Type 2 (2012+)'