Can someone confirm that this is the type of bottom bracket that I need?

My current bottom bracket looks like this:



The writing on it says:

BB - CT91
Shimano Singapore
via 68 vB
BC 1.37x24
YL 116
L <--- ---> R

Also, is this meant to happen?:



The entire side of one side of it comes off!

I have two bike frames that I need components for. This bottom bracket is fine, so i'm putting it in one of the frames. I need another bottom bracket like this one for the other one.

The link shows a variety of BBs so one can't really say if any of them is right for you. I would say that if your current BB is correct for your frame and intended chain line then you are safe in buying one with the same specs. Likewise if your BB fits the other frame - and the axle length is suitable for a proper chain line. Your other frame may have a different shell width and thread so you would need to check.

Also, yes one side will come off. You would not be able to install it if it didn't.

Here's a link to some info that may be helpful: Sheldon Brown's Bicycle Glossary Bo--Bz

Whoops, I meant the 116mm one. That's what the "YL 116" means doesn't it?

Both frames look exactly the same, the only difference is that one is 22.5 inch, while the other is 20 inches (distance between centre of pedal crank and where the seat post slots in).

I'll measure the shell width now.

have you anything to measure with? can you take that with you to a Bike Shop ?

Probably JIS taper .. 1.37 x 24 says it fits a regular British thread BB .. If you got a Italian Bike its Not the thing

the spacer on the right side is removable. other than that you are on your own..

Commonly a MTB ads 5mm to shell width .

The length of the spindle is determined by the crank, not the frame. Bottom bracket shells are standard width (given the type of frame), so how the spindle fits into the crank itself is what determines the spindle needed. If the 116 mm works fine with your current crank - if it gives you the proper chainline - that's all you need to know. If it gives you a chainline either too far inward, or too far outward, that can help you determine which one to get (i.e. shorter or longer).