BB axle length

[Gerard]

So if the frame manufacturer recommends between, 122.5 -125mm BB axle, and the crank set manufacture recommends 108mm for the correct chain line.....which do you follow.
(108mm does work, as does 110...just struggling with some chain rub).

Checked against Zenn and the Art.....and by those measurements the chain line on 108mm axle is within 2mm of 47.5mm chain line.

Just the front mech is not happy :facepalm:

 

[FluffyChicken]

Re:

is this an 80s/turn of the 90s frame?

You go crank size, they're the only ones that know how hey profiled it to get the chainline.

if you need to go 2mm more, do it (113 normally).
it could be wrong spacers on the granny ring or thicker rings than they used to have.
or you bottom bracket needs aligning a bit. depends what, how and if...

frame, crank, pictures, models, makes in questions always help.

.. 108 is usually RaceFace sort of number (107 is closest) up ?
107 should give 47.5 chainline, 110 should give you more to play with, its the same chainline but more on the none driveside if memory serves me right.it does mean you can add a spacer on the drive side..

 

[Gerard]

Re: Re:

is this an 80s/turn of the 90s frame?

You go crank size, they're the only ones that know how hey profiled it to get the chainline.

if you need to go 2mm more, do it (113 normally).
it could be wrong spacers on the granny ring or thicker rings than they used to have.
or you bottom bracket needs aligning a bit. depends what, how and if...

frame, crank, pictures, models, makes in questions always help.

.. 108 is usually RaceFace sort of number (107 is closest) up ?
107 should give 47.5 chainline, 110 should give you more to play with, its the same chainline but more on the none driveside if memory serves me right.it does mean you can add a spacer on the drive side..

Thanks. Yes RF Turbines, early ones. Frame is AMP B3. The Mongoose instructions in the archive suggest the 122mm etc. Frame is mid 90s.
I am currenty trying 110.
The chain line is 49mm.
The front mech works fine when on the stand, but soon as you are riding :facepalm:
I will play around with spacers. Middle and granny rub against the mech at the smallest 3 rings. I know you are not meant to use them but usually I can get it to work.