First time adjusting my EBB

[regan]

Hi all

New member here.

I have just completed over 1000 miles on my new Thorn Nomad and now need to make my first EBB adjustment.

Is there anything special I should be looking out for? The owners manual mentions the tight spot in the chain - how slack should I allow for this?

Any other advice for this nervous first timer would be appreciated.

Many thanks.

[julk]

regan,
welcome to the forum.

I would just take the obvious slack out of the chain, leave a bit in (about 1" movement) to avoid stressing the hub bearings and any tight spots in the chain/chainring.

If you use a rod into the EBB and turn it by rotating the cranks, pad the crank in contact to avoid scratching it.
I hope this helps.
Julian.

[pdamm]

Regan

A few things to consider (which you may have already thought of)

Keep the EBB centred within the bottom bracket.  It is easy to push it sideways and that messes with the chain line.

Rotate the pedals several times and check for tight spots throughout all of the pedal rotation before tightening the grub screws.

Make sure the indentations the grub screws put in the EBB are far enough apart so they are distinct indentations.  If they are too close then they become a grove in the EBB and don’t hold as well.  Use a small torch / flash light to look down the grub screw holes.

I was a bit too gentle with the grub screws on my first adjustment and the screws became loose.  Luckily I found out before they fell out altogether and lost one of them.  Check that they are not working loose for a little while after making the adjustment. 

Tightening one of the grub screws will make the other looser.  You need to tighten one, then the other, then back to the first, then back to the second, then back to the first and so on until you are happy with how tight they both are.

If you are particular about the height of your saddle you may want to adjust is after adjusting the EBB as it moves your pedals a bit.

Peter

[jimmer]

Dear Regan,

Prevent grub screw loosening by applying Loctite.

Don't torque down too hard on the screws. They only need to make a dimple c.2mm in depth & diameter in the EBB. Any more and you risk ovalising the EBB shell.

Yours, James

[JimK]

You don't want the indentations to get so close to each other on the shell that they overlap. I take one screw all the way out and look down that hole so I can see the existing indentations and either reuse one or pick a spot that avoids overlap. I then tighten the other bolt to secure that location, then replace the bolt I had taken out and tighten it down too.

[sg37409]

This talk of indentations.... Has anyone ever had to replace the eccentric shell ?

(sorry for partial thread hijack)

On topic, I think Thorn recommend not to have the EBB positioned with the thin bit at the screws, lest you pierce the EBB shell. I ran mine in this position though for a while with no ill effects.

As others have mentioned, check the tightness a wee while after adjustment. THey can come loose. I carry my wee spanner as a result of this.

[regan]

Thanks for all your advice.

It was surprisingly easy! Don't know why I was even worried. 

While doing it, my biggest concern was that without a torque wrench I would tighten the screws too much. I paid attention to how tight they were to undo and then tried to match that.

All seems good now. Nice straight, non-saggy chain.