what is this hole for on the bottom bracket?

[Maz]

It's the anus.

There is a reason it's called the bottom bracket.

 

[alecstilleyedye]

The name Alf Engers may mean something, if not Google it.


It drainage or lube I would imagine, I remember in my early days some bikes have a grease nipple down there.

my '51 claud butler still has the grease nipple on the bb. a lot of bikes from that era don't have them any more as they got removed when the frames got stripped and resprayed, apparently…

 

[Sheffield_Tiger]

It's also for the old-schoolers who believe that everything on a bicycle must be covered with a gallon of the highest viscosity oil, to pour in to ruin the grease, because any hole in a bicycle must naturally be there to mate with the flexible spout of an oil can

 

[tyred]

It's to save weight - like those rally pedals for cars with holes drilled in them.  

But it's such a tiny hole. Think how much weight I could save if I ran through it with a 1/4" drill bit

 

[02GF74]

hmmmm ...

heard that the holes in the seat stays are to allow gas to escape when the tubes are being heated when ,making the frame.

the hole on the bottom may be to take an alternative cable routeing pad - or whatever that plastic bit to hold the gear calbes in place is called.

not sure about the water out theory - the open ends of the framw would mean you are riding through water 4 ft deep or therabouts.

 

[Davidc]

It's to promote discussion on CC. It has no other purpose.

 

[Jezston]

But it's such a tiny hole. Think how much weight I could save if I ran through it with a 1/4" drill bit

You may as well make the most of that drill now you've set it up and get to work on your whole bike! Think of all the weight you could save!