Friday, 17 May 2013

Cannondale Trail SL 29ER 3 SS eccentric bottom bracket adjustment

First things first; to save anyone else the pain. If you want to adjust your EBB on your (lovely) Cannondale Trail SL 29ER, then you're going to need a set of small circlip pliers.

Now, I've always had a Park Tools set in my toolbox, but that was for the old self extracting bolts on Shimano and other branded cranks, but they were 2.2mm in diameter and that's way too big for the EBB. So if anything, spending today researching circlip pliers has taught me a thing or two.

What do you need to adjust the EBB?

Firstly. Go and buy a set of 44 11 J0 circlip pliers. There's probably no way you'll have a set of these in your mountain bike tool kit.

I bought the Knipex brand because they look like a good quality tool, but there's plenty of other brands available. They're even available through Amazon.

The tools you'll need to adjust the EBB

Here are the tools you'll need (in order they'll be used):

How to adjust the Cannondale EBB

The easy part
  1. Undo drive side 8mm crank bolt
  2. Using crank puller, remove cranks
  3. Undo 3mm silver allen key bolt on drive side
  4. Insert circlip pliers and remove circlip
  5. Remove washer
  6. Unscrew 4mm allen key bolt and take out
    1. Make sure you don't lose the circlip and bolt washer
  7. If you wish you can remove the bottom bracket too
It's likely the EBB wedges will be stuck (the hard part)
  1. Put a small flat headed screw driver / torx through the bolt 4mm hole and tap out the other wedge
  2. Repeat on the other side
    1. I had to bash mine pretty hard, but it did come out
    2. Spray with a threading solvent if it's really stuck and leave overnight
  3. The EBB will then slide out
Clean it up and put it back in
  1. Take it out, clean it up
  2. Clean the EBB shell so it's spotless (no need to add any grease)
  3. Put the EBB back in
  4. Do the 4mm bolt back up, but not all the way
  5. Add the washer and the circlip back in
  6. Put the bottom bracket back in
Now to adjust the EBB for desired chain tension
  1. Put the drive side crank back on (pushing it on by hand is fine at the moment)
  2. Hook the chain back around the chain ring and rear cog
  3. Adjust the bottom bracket position so that the chain is nearly taught (a bit of slack is encouraged)
  4. Poke a long 4mm allen key through your chainset and do up the 4mm bolt a little more
Final adjustments
  1. Remove the crank and do up the 4mm bolt to the recommended torque
  2. Add the 3mm bolt back in
  3. Tighten up the bottom bracket fully (you did clean and grease it right?)
  4. Add the cranks back on and tighten up the bolts
  5. Check to make sure the chain is still taught
  6. Fin
Overall this took me about an hour and I took my time to clean all of the parts and re-grease where needed too. It's important that you don't put too much grease, or any solvents / lubes etc in the EBB shell. Otherwise it will slip.


Here's the Cannondale EBB from the right (drive) side. You can easily see the circlip in the bore recess.

And here it is from the left side:

This is the EBB once it's out (and cleaned)

This is the bottom bracket that comes with the bike (UK)

Hope this has helped. I certainly wish I had read something like this before trying it!