Press fit BB bodged install?

thebluevoice

Hi,

Just changed my shimano press fit bb (new one is xtr since it was going cheap) using the proper TL-BB12 press tool but am having problems.

It now no longer shifts into the large chain ring (3x). I tried adjusting the barrel adjuster (many turns!) but still wouldn't engage large chain ring. That's not right is it? Shouldn't have changed?

Looking at the BB it looks flush around the outer edge but I notice there is an inner lip around the spindle hole which stands a bit proud. Is that right? My last BB (XT) didn't but looks a different design anyways...

Also removing the spindle from the drive side (to take the photos) was ridiculously hard, had to tap through lightly with the rubber mallet.

Turning the bearings with my finger they turn smoothly but with what I'd call "thick grease" resistance.

Attached is a pic of each side..

https://www.flickr.com/photos/71194847@N06/shares/DSX29J

*EDIT*

Hmm, more googling does show that inner lip standing proud so maybe that's by design. Just altered the barrel and h limit screw and got it shifting to large chain ring. Not terribly smooth shift though.
Also, more worryingly, I notice that in the large ring there seems to be more turning resistance forwards and backwards.. As if the chain is under strain?

larkim

New cable / reindex front mech? Worth doing anyway, even if anyone flags issues with the BB installation (I have no insights on that!).

swod1

Never used a press fit bb before but do you still need to use spacers like on bsa threaded?

This could be why its not shifting on to the larger chain ring, the crank could be closer to the frame.

thebluevoice

Hi Swod,

Yeah some use spacers but my bike is 92mm so not needing spacers. There weren't any when removing the old BB (checked to be sure lol).

Adding a spacer would move the rings further out giving the symptoms I'm having now, without a spacer doh!

I didn't think changing the bottom bracket would change the chain rings / chain line etc...

JGTR

I'd start from scratch with indexing. Set H & L then tension cable.

Large ring will have more "resistance" as it's the larger ring. Less leverage.

larkim

If changing tension on the barrel isn't doing anything it suggests either you're slackening the tension with the barrel (which won't help as you need more tension to pull across to the big ring) or you're hitting the limiter screw, so adjusting the correct one of those (I forget which way around they are). It might only take a very small difference in the chainring's location to stop the chain from shifting over.

thebluevoice

Ok I've reinstalled the cranks (4th time!), tapped home the drive side lightly with the rubber mallet to ensure it was fully seated.

Wound back in (less tension) the barrel to its former position and the H-limit back to it's position less .25 turn and it seems to be shifting to big ring again, albeit maybe not as smooth as before. Maybe my imagination though! Could be just a fine tune now.

Not sure what changed but guess the drive side crank wasn't on fully before despite also being tapped with mallet before..

I'll go for a ride later and see how it feels.

Many thanks all for your help

cooldad

When in doubt, whack harder.

thebluevoice

Went for a couple of laps around Cannock Chase and nothing terrible happened