the part of the frame BB Shell now comes in a vast variety of styles as well threaded types make replacing the Actual bearing assembly ever more rapid.


There were Zirk kits too grease goes in a tube between loose ball cups and adding more forced out the Old ..
WTB Grease guard went 1 up and puts a hole in the crank bolt, so that is a way the grease gets into the channel that leads to the internal route to do similar..

I built a touring frame in a shop near to the Burly tandem frame building and assembly shops so adopted their rear oversize cartridge bearing BB shell.

Butt (TIG) welded the 4 tubes to the outside of the shell and so the closed BB shell tube got a Zirk and the space between the bearings was filled with a good quantity of grease..

The bearing size I used are also used in automobile transmissions , like for Clutch throw out bearings..