my 2008 C'Dale bad boy disc (sunday bike), and especially my 2005 C'dale bad boy (beater bike), have rusty derailleur springs. They work fine, of course. Keep both bikes in clean, dry condition- in garage when not ridin. SW Ohio, USA. They're both seen rain, specially the beater, but I dry/clean right after a wet ride, and it doesn't happen often. Is this common?