I’m upgrading my Shimano Octalink internal BB with an external cup version, the one that comes with the 1x SLX groupset.

When I removed the old one, there was a drive side spacer, roughly 2mm thick.

The new one comes with its own spacers for a 68mm shell (2 driveside & 1 non-driveside).

My numpty question is…

Do I retain the spacer that came off the old BB?

Without it, I think I’m going to struggle to get the driveside cup tight against the frame (even with the spacers from the new BB).

I’ve not fully tightened either side up yet. Before I do, and start risking the thread, I’m after the advice of the STW hive mind.

Ideas welcome…

I assume you are also changing the crank arms ?

you can’t use old hollow tech octalink arms with newer external cups

Hollow tech and hollow tech 2 are very different things

Yes, is a whole drive chain replacement. Cranks, chainset and BB (going from 3 X 9 to 1 X 11).

Good good. Don’t add extra spacers between the bb cups and the frame as you will end up with to little axle for the left hand arm to fit on to.

Have you measured the frame shell yourself ?

Yes, 68.8mm without the extra spacer, so it didn’t seem like it should need any help.

But at maximum hand tight, there are still a couple of threads visible without the extra spacer in place.

Before I start applying real grunt, I wanted to sense check.

Yep two drive side and one drive side spacer is correct.

You can either get the threads chased through or just put the tool on and tighten it up

But it’s about how it feels as you it, personally if it’s gone almost alll the way in without useing a tool I’d probably just carry on.

I’d guess the new cup is going deeper into the shell than the old internal body did

Many thanks.

Sounds reasonable, I’ll give a few turns with the tool and see how it feels before pressing on.

Thanks again.