Eccentricity

Sadly, my Cannondale Trail SL SS 29er (to give the long name) has been grounded for some months now. I had issues with the eccentric bottom bracket (EBB), and after some internet searches it seems I'm not alone. The bike came with Cannondale's double wedge design eccentric - Part A181 for part number fans. The idea is that the two opposing wedges are brought together by a central bolt which secures the eccentric into the frame. Whilst the concept works fine, adjusting the eccentric could be an issue. A circlip and washer must remain above the bolt for it to undo the wedges - just like self-extracting crank arm bolts. Unfortunately for me, and many other 'dale owners, this circlip disappeared when adjusting the eccentric. Without the circlip, there is no way of adjusting the eccentric without making some amendments - unless, of course, you get the hammer out...

After a bit of forum searching, I found a method that worked fine for a short while. By tapping threads into the wedge that houses the bolt (on the left side of the diagram above), you can thread a bolt in there and, using the long bolt already with the eccentric, push the wedge from the other side. The forum post can be found here. This worked fine until I completely stripped the new thread that had been tapped - I suspect through poor tapping from the bike shop. This rendered the whole eccentric pretty much useless.

The eccentric can be bought new for around £70 but I really didn't want to get another one just to lose the circlip again and be back to square one. So I got myself a Bushnell featherweight eccentric. The general view is that these are well made, reliable and easily adjustable. 

The trouble is that they're not that easy to get a hold of. Charlie the bike monger has them advertised on his website but doesn't have any in stock. However, Fat Birds had them in stock. Fat birds are a ti specialist and a dealer of Van Nics who spec Bushnells on their single speeds.

Fitting was straightforward and didn't require the use of any particularly specialist (ie expensive and only used a handful of times). You will need a pin spanner to move the eccentric in the frame unless the BB has been installed and you can use a BB tool to move it. Other EBBs have hex key fittings to rotate it within the frame.

I will confess that I did not use a torque wrench, but applied a fair bit of oomph to the bolt. After 2-3 rides it hasn't slipped or creaked. Fingers crossed it will continue to do just that!

Other options include eccentrics from Carver Bikes, Phil Woods and Niner.