Bottom Bracket
What size bottom bracket do I need for my mountain bike?
Just got into building Mountain bikes, I've got a frame and need a bottom bracket. I know the standard shell is 68cm, but how do I figure what size BB I'll need? It's a 16" frame and it'll be 21 speed.
Cheers in advance : )
Mike.
First off, it's "mm" not "cm".
What you need to measure is the width of the bottom bracket area, just stick a measuring tape through the bottom bracket and measure how wide it is. Nearly all cranksets today will fit either 68mm or 73mm, the two most common sizes. They just use spacers to adjust the chainline and q-factor. If you have the larger 83mm bottom bracket, you need cranks with a wider axle to accomodate it.
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