How to choose correct BB width?

[not_fat_matt]

Building up a bike for my wife, but I'm a bit lost of what BB is needed.

Its got a 68mm shell and originally came with a UN-26 but I don't know the spindle width.

I'm swapping over entire drive train, from a bike that has a 73mm shell with a 110mm spindle, CN-HG72

Do I just pick the nearest equivalent, a 68mm with a 113 or 116mm spindle?

Hope someone can help

Cheers!

 

[The History Man]

Have a look at Sheldon:

http://sheldonbrown.com/bbsize.html


What cranks?

 

[FluffyChicken]

You would use a 68x110
In fact just use the 73mm you already have but get a ~2.5 mm spacer on the drive side.

But unless you have one or can grab one from a bike shop for nothing then you may as well just get a new bottom bracken given the cost
Un26 £6 delivered to your door http://www.chainreactioncycles.com/shim ... -prod34652

Un55 £12.50 delivered to your door
http://www.chainreactioncycles.com/shim ... -prod71369


The spindle length will be stamped on the axle near where it enters the casing, normally.

 

[elPedro666]

What Ben said ^
68x110

(just because a second opinion's nicely reassuring sometimes )

 

[not_fat_matt]

Thanks for the replys & links guys, very much appreciated