In a message dated 8/29/02 8:52:22 PM, classicrendezvous-request@bikelist.org writes:
<< Dear list members: Bottom bracket cutouts on steel frames-pleasing to the eye or invitation for internal rust (probably both)? I am tempted to plug the cut out with expandable insulation foam (the stuff in a spray can). Of course I have either an aluminum can or proper plastic bottom bracket sleeve but do not believe that this would protect the bottom bracket from the elements entering. I am not sufficiently fastidious to always clean after a ride. Any suggestions regarding keeping the elements out when there are cutouts in the bottom bracket? Thank you for your consideration. TomWitkop Rockville, MD >>
Bottom bracket cutouts are supposed to let moisture out as well as in. Let me tell you a story (second-hand, courtesy a local bike-shop owner). A rider was concerned that moisure entering the down tube around the stem (rain and sweat probably) collected in the bottom bracket and left some rust there (his BB didn't have a cutout). Rather than drilling a few holes to allow the moisture to drain, he put a plug of foam inside the downtube to catch the moisture before it reached the BB. Unfortunately, instead of evaporating, the moisture that was absorbed by the foam proceded to rust right thru the downtube and ruined the frame.
If you plug those holes with foam, something similar will probably happen inside your BB shell. Best thing is to leave things as they are and just make sure that your BB bearings are properly sleeved.
Bob Hovey
Columbus, GA