What size bottom bracket axle ?

Mike Muz

Mike Muz

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Hi folks ,

Hoping to pick some brains :roll:

I have just got hold of a Shimano M730 chainset for my Scott project , but am unsure what size bottom bracket to use with it . The shell size is 68mm , but I'm not sure what length axle it needs . I know that road axles vary in length , is it the same for mtb axles ?
Also , in your opinion , would a cup and cone b/b be more authentic in a '93 frame , or a cartridge job be more appropriate ?

Any help will be gratefully received , thank you kindly , Mike . :)
 
Around 120-122 mm, I think. I used 120 mm in my Scott Comp Racing.
It might depend a bit on the square of the arms. Two size exists, according to the JIS and the ISO standards. The JIS axles has bigger size ends if I remember well.
You have to match the axle with the arms...
 
unless you are trying for best in show, i would get a new cartridge from CRC from about a £10

s/be 122.5 i think - but google Sheldon Brown Bottom Bracket size and you will get to a data base that list out most of the shimano chainsets
 
122.5 was the standard length for the cranks and a cartridge bottom bracket is well and truly correct for 1993.

You would move to 127.5 if you only really needed to.

A year or two earlier and you'd be in Cup/Cone territory.
 
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