which bottom bracket length

steve1312

The missus bought me a ragley mmmbopframe for christmas.

I spent the weekend breaking down my bike and building the new frame. I have a race face evolve chain set. I have to replace the bottom bracket as the new bike has a 73mm shell.

I have been looking at a new Raceface srx BB but have got myself flummuxed reading about chainlines etc.

anyone know what axel length i need 108 or 113

Seat tube is 34.9

nicklouse

ISIS? 113mm as covered in the FAQs

bikaholic

The Race Face Evolve crankset will have a specified chainline for a given bottom bracket spindle length.

It's usually a 48.5mm chainline with a 113mm ISIS BB.

If the crankset was working fine on the old bike, then you'll just need a BB with the same spindle length but with a 73mm BB shell instead of a 68mm one.

nicklouse

bikaholic wrote:

The Race Face Evolve crankset will have a specified chainline for a given bottom bracket spindle length.

It's usually a 48.5mm chainline with a 113mm ISIS BB.

If the crankset was working fine on the old bike, then you'll just need a BB with the same spindle length but with a 73mm BB shell instead of a 68mm one.

And for ISIS most of the BBs are both 68 and 73mm

bikaholic

Another useful thing to know is that some BB tools are approx 0.5mm out of spec and so may not fit around the central part of the BB spindle (the smooth bit just inboard of the splines) - so check that your tool fits.

steve1312

thanks for the quick responses.