I've been slowly going through the process of converting my old hardtail mountain bike into a commuting bike. One of the things that I'd like to do is to fit a chain guard so that I can ride the bike while wearing long trousers and not have to worry about chewing up the trouser cuffs.
A complication is that the bike (like most mountain bikes) is fitted with both front and rear derailleur gears. I'm not keen to replace these with an internally geared hub system as I have been trying to keep the changes relatively modest in their cost.
Are there chain guards that you can add to bikes with derailleur gears?