Bottom Bracket upgrade from a one-piece crank?

[krashTest]

I know this question has been asked a million times, so I will add another to the count

The bottom bracket as seen in the attached pic is of a CCM (Canadian brand) entry level bike from the 80's. The diameter of the shell is 2 inches, roughly 50 mm. There are no threads.

From what I've read, it appears that I need an adapter kit to fit another type of bottom bracket? What are my options? Are there any advantages?

Thanks in advance.

[DaveM]

You would need the adapter, a new bottom bracket, new crank, and new pedals.
The conversion will shave some weight off the bike, look a bit cooler, and give you more choice of crank/pedals, especially if you're trying to get gearing set ups you can't get with a one piece. But the bike won't really perform much differently.

Whether it's "worth it" or not, I can't say. If the bike has steel rims, upgrading to decent quality aluminum wheels will likely make a much bigger difference in how it rides.

[krashTest]

My main concern is understanding how to measure or select an adapter kit suitable for this shell and whether it limits choices for the type of bottom bracket I would have to install.

Thanks for the note regarding rims, I haven't given it much thought beyond wanting to upgrade them as well. The current steel rims are cheap - spots of chrome is removed and there are stress lines along the nipple holes.

[nfmisso]

This is your cheapest alternative:
http://www.amazon.com/Pyramid-Piece-Bottom-Bracket-Conversion/dp/B000AO9O12/

but as one of the reviewers suggested, spend a bit more and use a cartridge BB:
http://www.amazon.com/BB-Conversion-Bp-American-To-Euro/dp/B001G8TSPS/

[krashTest]

Sweet, thanks Nigel!

[1FJEF]

Does he have to check that the BB opening is 68mm wide? His frame looks like it has a recessed "lip" area around the BB opening. Won't the adapter have a gap between the back of it's flanges and that frame area?