Have an Alfine hub/Bushnell EBB on my Salsa Selma. It’s become prone to the chain skipping off at random moments when just riding along, over small bumps etc.

It was set up as it is by my LBS a while back.

Seems to be quite a bit of slack in the chain – would shortening it by a link or two, or rotating the bottom bracket further away from the rear cog, or some combination of the two, cure this? Do you need any particular tools for adjusting these bottom brackets? Do I need a new chain? Or would I be better off getting some kind of chain-keeping device that attaches to the bottom bracket?

Thanks in advance for advice…

check the chain for wear – easiest using a specific tool but you can measure the chain length.

if chain not exessively worn then adjust slackness out using the EBB.

I’d also check the chainline – even with a slack chain it shouldn’t just jump off like that.

You just need to rotate the EBB to take up a bit of slack.

Check your chain line is straight.
Use an unramped 1/8in chain and SS chainring.
Check your chain line is straight.
And
Check your chain line is straight.

How slack is your chain? I work on being able to lift it 1/2-3/4″. Any more than that then tighten up your ebb

brant – Member

Check your chain line is straight.
Use an unramped 1/8in chain and SS chainring.
Check your chain line is straight.
And
Check your chain line is straight.

If you only have one cog at either end and no derailleurs, what do you adjust in order to achieve a straight chainline?

if it’s an EBB you can usually move the bit holding the BB side to side a bit (and thus move the chainring) once the retainign bolts are undone.

If the chainline was alright to start with. . . . .

If you only have one cog at either end and no derailleurs, what do you adjust in order to achieve a straight chainline?

Chainring location, BB spacers.

Use an unramped 1/8in chain and SS chainring.

Not on an Alfine. The Alfine cogs are designed for use with a 3/32″ chain such as a normal 8spd.

I had a 1/8″ chain on my Alfined 29er Inbred for a bit, and nothing I could do would stop it throwing the chain off. Swapped the chain out for a cheapo 8spd KMC Z chain, and I couldn’t get it to throw the chain off once. But yes, an unramped chainring makes sense.

If you only have one cog at either end and no derailleurs, what do you adjust in order to achieve a straight chainline?

Aswell as the good suggestions above, with the alfine rear sprocket you can “cheat” about 5mm of chainline adjustment at the back end.
It’s a dished/offset cog , so by turning it round you alter the chainline by about 5mm.
You may have to remove the plastic chainguide ring to re-lock it in its “backwards” position but, TBH, it’s not needed anyway once you get your chainline straight. 🙂
But before you do any chainline alterations, make sure the chains not to slack first.

It sounds like it just needs adjusting, that’s what the EBB’s for.

Assuming it’s a wedge type, there will be a socket cap bolt head on the left hand side.
Loosen it all the way, then turn the whole unit to move the BB forward. I use a BB spanner for this on the cup.
Make sure the tension is right and the sideways position, then tighten the bolt again.