Square Taper Bottom Bracket Query
 

Hi !
My bike Btwin fitness 1.
There was some play in my bottom bracket and I opened regreased and tightened it.
The brand is a Vp .
Thought I should install a shimano instead.
Following is the specification with images:
http://imgur.com/a/AbRVK

After checking the measurements with a scale and reading the sticker , i realised that the available shimano bb are of 68x 118, 68x122 and 68x 122.5.

Since i need a 68 x 120 , which size would be appropriate, I am unable to source the same size.
What does the BC 1.37x24T stand for.
Should there be any other specifications that I need for a bottom bracket sizing.

Is this a multiple gear bike?

atlantis, How much clearance is there between the chainrings and the chainstay with the present BB? You may be able to use either the 118 mm or the 122.5 mm BB.

Brad

The 68 x 118 will move the chainrings 1mm closer to the frame while the 68 x 122 will move the chainrings 1mm farther from the frame. Doubt either would be an issue.

+1 Either the 118 or the 122 should work, unless the 118 would put the inner chainring so close to the chainstay that the chain would rub. That's not likely, though.

I could be mistaken, but I think BC refers to British (English) threading. 1.37 (inches) is the inside diameter of the BB shell, and 24 is the number of threads per inch (tpi) on the BB shell. Alternatively, I suppose you could say that 1.37 is also the outside diameter of the BB, and 24 is the number of tpi on the BB cups.

The gap is about 6mm

Yes its a triple chainring 48*38*28 and 13-26 7 speed cassette

Just wondering would the chainline get disturbed if I use a bb with a slight variation ?

The chainline will move ever so slightly. If you think about it, the derailleurs are going to move the chainline all over the place anyways.

Brad

Perfect chainline is only an issue with 1x1 bikes like fixed gears. You can get either the 118 or 122. You may have to adjust the limit screws on your FD so that you don't throw the chain off, but that's not a big deal.

Again, you're chainging chainline 1mm. As you have a 3 x 7, check the alignment of the middle ring and middle cog. I would be surprised if they ar perfectly in line so buy the BB that will bring them closer (if the chainring is lined up to the ouside of the cog, go with the 118 / if the chainring is lined up to the inside of the cog, go with the 122). If, by some miracle, the chain line is perfect with the original BB, moving it 1mm won't hurt and you can go either way.