Facing BB shell on steel frame for external BB?
Is it a good idea? Or will it expose the bare metal and allow for corrosion, which could cause more trouble than having an unfaced shell?
If it needs facing, face it. If not, don't. Simple as that. In regard to your rust worries, the bb cups will press against the bb shell's faces. Put a good bit of grease on the bb threads, by the time the cups are screwed in tight, you'll have grease between the cups and shell anyway.
Last edited by well biked; 03-09-10 at 05:44 PM.
I face it. You are going to damage the paint anyway.
If the bearings screw in flat against the shell and if you can slide the crank axle through the bearings without it binding you are probably OK
You sometimes have to face the shell to make up for the build up in tolerances in both the shell length and crank axle length