View Full Version : Bottom Bracket Shell

10-10-2009, 07:20 PM
Hello all;

Does anyone know where bottom bracket shells can be purchased?

I found someone who sells - 68 and 70 mm BBs shells.

I have a couple of bottom brackets on bikes.....

one a nishiki prestige (used to be a road bike) the inside diameter is 2 cm (measured with a caliper)

the other a broken down mtn bike I picked up at a salvage sale (for parts) has the same size - 2 cm ID

I was looking for a shell that would fit in a space - 27 CM inside diameter -

that I could weld inside.

Regards; Paul

10-10-2009, 07:42 PM


A tip, if you use both mm & cm in measuring objects, you will easily confuse yourself and end up cutting a part too short or too long. The smaller the measure the greater the accuracy, i.e. a BB could have a diameter of 71.5mm , in cm that would be 7.15, but you now have a problem where you cant find .15 of the cm on the ruler so you round it to 7cm. Marking it out as 7cm, you could be a mm or 2 off your mark either side. Little bit out here is a LONG way out down a highway when you are measuring sequentially :jester:

So work with the smaller measure, & you will have greater accuracy.

I am qualified as a Mechanical Engineering Draftsman, and a Civil Engineering Draftsman, with Architectural Drafting experience as well, as well as being 4 subjects short of being qualified as a Mechanical Engineering Designer and a Civil engineering Designer and I often use 0.5mm in my drawings to ensure accurrcay accuracy.

You have 70mm of clearance to play with, so use your donor BB from the DF mountie, cut to nicely fit into your opening, so that is positioned where you want it .


10-10-2009, 08:25 PM
Here are 3 sources for lugless threaded bottom bracket shells.





10-11-2009, 11:56 AM
Thanks for the links - that will help.

My main confusion with measurement was - I was told there are 2 standard sizes for bottom brackets - 68mm and 70mm.

what I measured on a 2 bikes I have is (2cm with a caliper) (and 3.5mm with ruler same BB)

is there that much of a size difference with japanese bikes (bottom brackets) and the 'standard'?


10-11-2009, 03:41 PM
If you are getting 16.5mm (20mm-3.5mm=16.5mm) difference between measuring the same object, I would throw out the ruler and triple check the accuracy of your vernier, before progressing any further.

Most BB are made in Japan or some other Third world nation for the cheap labour, and the measurement you have given are when you measure the BB across the the faces with the threads in them, and 2mm is not that much difference.

2cm or 20mm difference would be a huge difference.


10-11-2009, 05:13 PM
...Japan or some other Third world nation for the cheap labour...
are you sure that this is what you were trying to say :rolleyes4:
Japan is not cheap and definitely not "third world"

BTW, best place for info is this site (http://sheldonbrown.com/gloss_bo-z.html#bottom)
Looks like yours might be OPC?

10-11-2009, 07:45 PM
I was hoping to find a bottom bracket shell the same size as the bottom bracket assembly and pedals I already have -

but the measurement I came up with (2cm, = 1-1/16inch, = 3.4mm inside diameter )

I can't seem to find the same size shell.........(I think I'm measuring wrong )

I know these bikes aren't rare - so I should be able to find something -

or complete BB shell with BB that will fit my pedals.


10-12-2009, 03:36 AM
are you sure that this is what you were trying to say :rolleyes4:
Japan is not cheap and definitely not "third world"

I was actually meaning Japan(not cheap but precision built), or some other third world nation (cheap and semi-precise in build quality) just missed the comma


10-12-2009, 03:59 PM
Maybe someone can answer this question?

The space I need to fit the bottom bracket shell in is 2 inches -

would a 68 or 70 mm bottom bracket fit in that space?

in other words is 68mm/70mm less then 2 inches?


10-12-2009, 04:20 PM
Hey Paul,
I think 25mm is about 1" so you should have plenty of room to spare.

10-12-2009, 04:27 PM
OOOOPS, Brain fart! it is way to big.

10-12-2009, 04:32 PM
looking at bottom brackets shell I just realized - 68-70mm is the width -

not the inside or outside diameter......

so 25mm ID to 68mm W - - - - - - works (duh agrivating!!)

OK thanks; Paul