BB68/BB30

[mrcunning]

Right slightly puzzled,ive been offered a cheap carbon frame and im wanting to build it up..midlife crises/hobby im not sure yet.
Which is the better frame size hole to have for the bottom bracket? Has the bb68 got any limitations? and shimano/sram groupsets are these compatible..
Im building this bike mainly to mess about and use it for a indoor winter bike..2nd thing is what are one of the better indoor training frames..thanks in advance .

 

[T.M.H.N.E.T]

Those are different dimensions. 68mm and 73mm refer to the width of the BB shell (73 commonly found on MTB's)

30mm refers to the axle diameter. (ie: Hollowtech 2 is 24mm)

The limitation is the frame in whether it's a threaded or press fit shell.