BB eccentric torque

[mountaincarrot]

Hi

I'm building up a Enduro having bought a secondhand frame. The EBB shell probably has 5 or 6 bolt imprints in it at the moment, but it also has a long circumferential score where it's clearly twisted.

Is there a recommended torque for the bolts?
 
Would it make sense to take a couple of turns with a pointed drill (say a countersink bit) to deepen each existing hole and ensure it can't slip in the future?

Thanks

[PH]

You can download a Thorn owners manual from here;
http://www.thorncycles.co.uk/downloads.html

It gives the torque as 10 to 17 Newton-meter.
I’ve no idea what that means!  Just tighten it up without forcing it and it’ll be fine, the hard steel points on the screws easily make their own indentations in the soft aluminium case.  The slippage was either the previous owner being over cautious or the screws becoming loose (happened to me once, don’t know why, never happened since)

[tynevalleycommuter]

mtc - its not too clear from your post whether the bolt imprints are from 'pointed' bolts or flat ended bolts. If you have 'ordinary' bolts, changing to pointy ones should ensure that they bite in OK.

[tt2cycletours]

Hi, I have the same situation - bought a second hand frame and the EBB had many indents.

Are there any alternative to buying a new EBB shell? 

Is a metal filler a way to resurrect the aluminium, are any tough enough?

Could I drill a holes the same diameter as the bolts, so to fix in one position.  Can you get away with one (as instructed by thorn) EBB position for life of chain?

As a side point - is steel bolts into aluminium really the optimal solution, surely there are other methods to stop a cylinder of aluminium from rotating??  Would pre-drilled holes not work better and remove the margin for error.  It doesn't sound like this is a rare occurrence.  I have adjusted the EBB three times in three months! And I do have a torque wrench. 

Thanks, Tim

[mickeg]

One of the screws in my Nomad bottom bracket shell came loose and unthreaded itself enough that when I noticed it I was concerned that I could have lost it.  I suggest you put a bit of grease on the bolt to reduce the chance that it vibrates loose.  I put a bit of blue loctite on mine, but I think I would have been better off with grease instead, the locktite makes it harder to turn than I would have liked.

[tt2cycletours]

Any prospect of refurbishing a EBB aluminium cam; I guess not.  The EBB has back rotated I have the chain significantly looser than the recommended but actually I can't see/perceive any problem have a fairly loose chain, certainly hasn't come off in over a 100 miles so I am wondering if I can make do with imperfect chain tension. 

Tim

[JimK]

It has been rather typical for me to discover by the chain falling off that I need to adjust the EBB! When the chain is loose enough to fall off, it goes back on pretty easily too! I think the only real downside is whatever possible awkwardness from the chain falling off at the wrong moment.

Now that I have a chainglider installed... I can't see the chain falling off very readily! I suppose I should still adjust the EBB every once in a while, on general principles!

[John Saxby]

metal filler a way to resurrect the aluminium, are any tough enough

Just re-reading this thread, Tim, and on your question of a new EBB or refurbishing the alu:  Wellll, I have used J B Weld (a metal epoxy cold weld made in the states) for all manner of things over the years, and it's tough as anything, harder than alu or close alloys. BUT, I've only ever used it for external crack-filling and repair, and occasional small joining projects where there's a large enough mating area between the two surfaces being joined. On an internal arrangement like the EBB, I'd be worried about not getting the repair suitably filed/sanded down so that it's as round as the original (I have only hand tools for such jobs), with the possible result that the friction of the EBB against the frame is unevenly distributed, the adjustment rotation is thus less regular than it needs to be, and your possibility of slippage remains. Even more, I'd be worried about the whole affair seizing, so that you have a serious false economy. Easy for me to say, but I'd splash for a replacement EBB.

Then again, Jim just above has a trick plastic work-around!