Bottom Bracket Mounted Front Derailleur

[Bong]

I am overhauling my wife’s 12 year old trekking bike which is based on Shimano Altus. The bottom bracket is a nasty cup and cone job which I intend to replace with a Shimano sealed BB (UN 54 on offer at Chain Reation Cycles). The front derailleur is fixed to bracket which is mounted on the BB. I have noted from elsewhere that for one axle length at least (too short for my needs), there was a BB mount option. I have not been able to find out how this may have been special.


Does anybody have any experience of this type of assembly? Having finally got the old fitting off, I can visualise that the derailleur bracket is held in place on the right hand side by the body of the BB and the left hand cup then screwed in from the other side. I suppose that this would mean the bracket/axle is offset to one side by the thickness of the derailleur bracket (1-2 mm).

Is that likely to be a problem? I don’t imagine so but any advice/experiences appreciated. If all else fails I will get a new front derailleur for a fiver, but it would be nice to know in advance – the bits are dure to arrive over he week. Thanks for your help.

 

[PpPete]

I came across these for the first time recently.
I put the old cup & cone BB back in after cleaning and regreasing it ... couldnt see the point of putting a sealed one in. But the BB mounted mech was seized solid and as I had another front mech with the right size seat tube clamp I used that rather than buying a new Altus mech even though so cheap.

Wouldnt have thought a chain line variation of 1 or 2 mm is going to make much difference, but check the "flange" on a sealed BB big enough to hold the mech?