Drill Hole In Bottom Bracket Shell
 

Always seeing water contamination when I remove bearings form the BB. I want to drill a 1/8" hole in the bottom middle to help drain water..Aluminum frames.

I can't see any harm in doing this, but I assume this will void the frame warranty.

Anyone else try this? any cons?

Thanks

.
...I've not seen it done in aluminum, but it's common practice in steel.

With an aluminum BB shell, I'd be more inclined to recommend just installing a sealed BB cartridge unit, and trying to figure out where the water is entering your frame and eliminating those pathways. The seat post/seat tube interface is a logical first stop.

The cons are the obvious greater susceptibility of aluminum to cracks that will form and radiate from the hole in many cases with aluminum tubing. You might be OK in something as heavy and thick as a BB shell, and in fact, I'd not be surprised to see some of them with under the shell routing for the cables. The plastic thingie for the cable routing is often just glued in place, however.

I in an earlier post asking about fixing the plastic cable guide under the BB shell offered a drilled hole, with a pop rivet..

once the pop rivet is fixed, the inner end expanded, the pin that does that breaks off, in the jaws of the pop rivet setting tool,

and the ball on the end that is doing the expanding, can fall out, once it is done,

both securing the cable guide, and leaving a hole in the center of the pop rivet.. your drain..


worried about 'voiding the frame warranty' have the dealer that you bought the bike from, do the work.






.....

The warranty issue might be the only con, if your frame has a lifetime warranty, and you're the original owner. If neither are true, go for it. You could go bigger than 1/8" even.

Welded frames almost always have vent holes in the frame anyway, so water will both be able to get in, and also evaporate. So adding one in the middle of the BB shell isn't going to cause any structural problem. But it would be better to tap the hole and put in a screw, so you can drain when needed.

I use 3/16” or 4.5mm drain holes in B.B. shells. It’s important that they’re not blocked by the cable guide.

There are likely millions of AL frames with a BB hole, locating a BB cable guide, without any issues. I wouldn't loose sleep. Andy

:innocent:

...nttawwt. :)