Is there a “standard” distance? On a MTB frame etc etc. I’m guessing there’s a lot of variables?

Its not from the shell face but from the centreline of the frame.

Its called the chainline and it’s measured to the middle of the tripple ring on a standard MTB. Usually 47.5mm nowadays.

http://sheldonbrown.com/chainline.html

OK cheers, yeah aware of chainline. OK. So is there a standard distance from the centre of the frame to the BB shell face?

depends on BB shell size. Two standard sizes 68mm and 73mm.

so for distances you can work it out based on chainline – half shell size.

73mm. So the BB shell will be central with respect to the frame yeah? So looking at 11mm distance between shell face and chainring.

Ta 🙂

So the BB shell will be central with respect to the frame yeah?

unless its SARACIN 😉