Adjustment of eccentric BB

[Al Downie]

Hi,

I'm wondering if anyone could explain what the two bolts under the EBB actually do? I'm sure I read somewhere that they deform or puncture an internal sleeve, which locks the EBB in its position. I'm a bit alarmed by that, because it suggests that there might be a finite number of adjustments one can make before that sleeve is damaged beyond use. I also read a report by someone who lost one of the adjustment bolts on a tour, presumably because he didn't have a torque wrench and wasn't able to comply with the very specific recommendations given in the Thorn instructions. Both of these factors are putting me off the Thorn bikes, and I'm leaning towards an Orange P7 which has a sliding Rohloff dropout instead of an EBB for chain tensioning. Can anyone put my mind at rest and steer me back into the light?

[JamesBradbury]

I think you're right that they bite into the metal housing of the EBB.

However, I've heard that you probably won't need to adjust it very often, especially after the first time. I guess this is because the chain stretches fastest when it's new.

There are also some guidelines about how much chain slack is ok and how to measure it.

Chances are by the time you've adjusted it twice you'll be wanting a new chain anyway.

[jawj]

Hi Al, this kinda worries me too, but it HAS to be easier than the P7 system, even it means replacing the internal eccentric every couple of (2? 5? 10?) years.
(Take a peek at my post in your main thread on this)

[PH]

quote:Originally posted by Al Downie


I'm a bit alarmed by that, because it suggests that there might be a finite number of adjustments one can make before that sleeve is damaged beyond use.

The bolts, or to be acurate set screws, are pointed, when you tighten them the first time they make the indentations. That isn't damage, that's how they work. If you want to use this position again they'll fit the same indentations and do the same job.  The only restriction is that you can't subsequently make another indentation next to an existing one, the screw will just slip into the old one. No big deal as you don't need that level of micro adjustability to keep the cain tight enough.  This isn't new technology, it's been used on tandems for years.

EDIT - Nearly every Rohloff specific bike I've seen uses an EBB.  Those that don't tend to be multi purpose frames or one offs.

[stutho]

Hi Al,

It sounds far more alarming and complicated that it actually is.  Honestly it is very easy and not something to worry about at all.  Tandems have being using this system for years.