should bracket be flush in EBB?

[strictnaturist]

Hi all

I have the newest  Mercury model ( one year old) and have noticed the bottom bracket is slightly to one side of the EBB? It pokes out about 3 or 4 mm the drive side. Is this OK?
It must have been like this since new, but just checking it shoudn't be moved flush with the EBB? I slackened the bolts off. The whole EBB moves right to lerft quite easily , but the bracket doesn't budge in the EBB.
All well I am hoping?
thanks for your assistance
SN

[Danneaux]

I always take care to make sure my EBB is flush with the shell in order to preserve my chainline -- which was calculated on this being the case.

It sounds to me as if something has shifted.

You can check the chainline by looking at the distance between the centerline of your seat tube and the centerline of the chainring (actually, easier to measure between chainring centerline and right side of the seat tube, the add half the seat tube diameter). It should be either be spot-on or very close to Rohloff's recommended 54mm.

Best,

Dan.

[strictnaturist]

Thanks Dan, Looks out.
Do you just tap the bracket along into position, or is a pully type of adapter required?
cheers
SN

[Danneaux]

I make sure my eccentric "slug" is well greased so corrosion is not an issue. I have had good luck loosening the bolts, then using finger pressure alone to center the eccentric on my bikes (both my Nomad and my tandem use eccentrics). On others' bikes, I have sometimes had to resort to a gentle tap or two with a non-marking lead shot-filled plastic hammer on the edge of the eccentric. A small lump of wood between a conventional hammer and the eccentric would also do but should not be necessary unless there is corrosion present.

Best,

Dan.

[JohnR]

While the Speedhub manual says 54mm chainline https://www.rohloff.de/fileadmin/user_upload/ENGLISH_OEM_36_2014.pdf, the specs posted at https://www.rohloff.de/en/experience/technology-in-detail/specifications indicated that the 54mm is for threaded spockets and the required chainline for splined carriers is 55mm or 57mm depending on the splined carrier used. Measurement and eyeball suggest that 55mm is appropriate for my Mercury (the eyeball test is to look from the back of the bike and see if the line through the sprocket and chainring is parallel to the bike while measurement is from the centre of the "o" in "Thorn on the bottom of the bottom bracket to the axis of the chainring). The EBB moves laterally within the bike's bottom bracket but the cartridge is screwed into the EBB and won't move laterally. My EBB is offset slightly to the right but I've fitted a steel chainring approx 3mm thick to work with the Hebie Chainglider. This chainring is thinner than Thorn's standard fitting and reduces the offset from the spider so the EBB has to be moved laterally to compensate. 

[PH]

I'm not sure what we're talking about here. an EBB is a system rather than a component, there's the shell as part of the frame, the insert which fits into the shell and there's the BB itself.
If the insert is offset in the shell, just loosen the bolts, take some tension off the chain and push it back, if it doesn't push easily, take the chain and one crank off, remove it, clean and grease and try again (It's a good idea to remove and grease from time to time anyway)  If you're having problems getting the insert out of the frame, there's a Thorn video somewhere. Thorn will have chosen the components to give the right chainline with the insert flush. Well, I find it hard to imagine they wouldn't have.
If the BB isn't flush with the insert, that may be normal depending on the type of BB/crank you have.  The left side loose cup of a Shimano ST often sticks out a couple of mm. 
If you have any issues a photo would help.

Are you sure it hasn't always been like that?  Have you re-tensioned the chain? It's quite easy to move the inset to one side when doing so. 
I have in the past deliberately run an insert a couple of mm off centre to get a perfect chain line with an older crankset.  There's no harm in doing so, there's plenty to clamp onto.

[JohnR]

Here are photos of the BB on my Mercury. I reckon that, for a 55mm chainline, then a line through sprocket and chainring should intersect the inner edge of my forks which use a 110mm Boost axle.

[strictnaturist]

Thanks for all your help here. These comments and photos certainly helped. With my BB shell flush, the internal catridge sticks out by about 3mm? More than likely as was delivered a year ago. The shell moves very easily when the bolts are loose, but as John R has indicated, the catridge is scewed in. Not pushed, as I had thought. Requiring further mechanicical time / know how to adjust. I have just changed Rolhoff oil the front chainring to lower the gear a bit, with acompanying new chain. I thought this might have contributred to a move, but as ithe catridge is scewed in. Less likely?
Just got to identify where the rumbling noise coming from rotating the crank is coming from now?
Yikes. Hopes its not the hub?
Thanks all
SN

[geocycle]

Rumbling noise when rotating the cranks? I’ve had rumbles when the bottom bracket needs replacement or service. Or it is the chain not meshed with the chainring or sprocket. Is the chain too tight? A hub problem is unlikely although check the skewer is not too tight.

[PH]

Depending on the BB type, 3mm sticking out might be normal, I only have experience with Square Taper and they don't normally come loose, just the opposite!
If you've changed chain and front ring, the chain might not be meshing with the sprocket, maybe flip that over if you haven't already, or try a replacement if you have (If that makes no difference, swap back, you'll need it at some point) The only thing to be really cautious of when playing with the transmission, is not to overtighten the chain, the hub won't like that. 
There's plenty of youtube videos to guide you to general BB maintenance, I like Park Tools info, I both trust it and find it entertaining.