I'm tired of getting grease & grime on my right pant leg even with trouser straps, and I don't much want to wear full gaiters. My bike has a standard 3x9 Shimano mountain drivetrain. Can anyone recommend a chaincase that would protect my pants from brushing against the side of the chainrings and chain? I understand that it's much easier to design a chaincase for a drivetrain without derailleurs (especially for coverage above the chain), but doesn't anyone make one that works on a bike with front (and rear) derailleurs?