Bicycle Mechanics - Adding a bottom bracket cut out?
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05-22-11, 01:10 PM
I have a steel frame that needs a repaint due to the rust. It doesn't have a bottom bracket drain hole and I was thinking about adding a small heart cut out, probably only 1/4-1/2", but I wanted opinions and wanted to know whether it would be safe. I know drilling into tubing on a bike isn't safe, but I don't know about a bottom bracket shell.
05-22-11, 03:13 PM
Done properly I expect it's perfectly safe. Several of the famous Italian frame makers did it routinely. That said, it sounds like an opening big enough to allow a lot of water to enter the shell as well as drain out. My vote is for a 1/8" hole.
05-22-11, 03:58 PM
They also did the cut outs to cut weight on the bb shell. I don't know if I'd do it on bicycle ridden on a normal basis as it's just asking for more debris to enter your bearings and have to service them more often. A lot of the bikes with cut outs on the bb shell were race bikes and always being worked on so it wasn't an issue. I'd just leave it and why does it need a drain hole? I don't remember the last bike I've seen with "drain holes" besides older high quality race frames. They never put them on standard frames cause it was never needed. What are you doing that it needs a drain hole? Even if it's an everyday commuter just use a newer cartridge bb or use some good quality grease and it should last awhile before needing repacking.
05-22-11, 04:10 PM
Mega ditto's on what HenryIII says. You're looking for a solution to something that's not a problem.
05-23-11, 11:02 AM
You can put a hole in it if you want,no problem.
05-23-11, 11:17 AM
Probably already has, at least 1 hole in there,
for the screw for fitting the plastic cable slider/guide..
a drain for condensation is good.
05-23-11, 11:30 AM
I vote for a cool cut out, make it your own. Just remember it's going to take a lot of work and you have to clean up every sleel shaving. Post on framebuilders with pictures or ask for help/ ideas.
05-23-11, 07:36 PM
I'd just leave it and why does it need a drain hole? I don't remember the last bike I've seen with "drain holes" besides older high quality race frames. They never put them on standard frames cause it was never needed.
Every bike I've seen in the past decades, including '83 and '87 Trek steel frames, a '92 Trek Al frame, three current Litespeed Ti frames and a '98 Co-Motion steel frame all have bottom bracket drain holes in addition to the hole intended for the bottom bracket cable guide. Drain holed are nearly universal as far as I can tell.
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