in the early 90's for the first gen OCLV road frames, Trek supplied a large stainless steel 'washer' to install behind the drive side bottom bracket cup to prevent chain drops / suck from jamming and/or sawing through the frame
Trek did this after a number of reported incidents
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The bike that got really stuck was a Rivendell Atlantis. The guy would sometimes bring it on climbing rides and smoke nearly everyone. He said it was 28 pounds.