How do I find what axle length I need?

[Panter]

If the hole in my frame that the BB sits in is 68mm across and the cranks are 30mm wide each, what size BB would I need?

 

[Mr Pig]

The best idea is to take it out and take it to the shop with you. Many have a number on them but even with that I've still been given the wrong one.

 

[Panter]

Thanks Mr Pig, that's the problem though, I don't have the old one.

I just have the frame I bought from fleabay and the cranks.

 

[Jonathan M]

What make cranks, are they square taper or splined?

 

[Panter]

Splined, they're Truativ isis if that helps.

 

[Mr Pig]

that's the problem though, I don't have the old one.

Ah.

Maybe the seller will still have the BB, you could ask. Failing that you'll need a knowledgeable bod who will know how to measure it and work it out.

 

[Panter]

Snag number 2, I bought the frame about a Year ago and have only just started on it

I asked the same on MTB Britain, the opinion was to play safe and go for the longer of the ones on offer as then the BB would definately fit.
If it's really no good I'll have to send it back but I've orderd the 118mm one now <hopes for the best>

 

[Mr Pig]

Why not take the frame to a good shop and ask them to figure out which one would be right? Might be easier than you think.

 

[Gerry Attrick]

Have a look at this, particularly with regard to chainline.