Hi - first time post!

Literally got forced in to bike maintenance last week after my commuter bike's BB bolt sheared off (UK Carrera Kraken 2010). I wanted to do it myself so ordered a replacement BB - truvativ 118 x 68 power spline sealed unit. It was a straight swap but on tightening up the left adapter cup (non-drive side) I noted that the adapter was not flush with the frame - it sits about 3mm proud with thread showing (couldn't upload pic :/). I should've taken a pic before disassembling to see if this was normal, but didn't. It's all been well tightened both sides and no issues with thread. But when I replaced the crank arms and went through the gears everything was well out. I'm part way through trying to calibrate them all but just wondered if a) it's normal for the non-drive side adapter cup not to sit flush and b) is it normal to have to rejig all the gears after BB change out?

Many thanks in advance!!

boz.

The nds cup on cartridge bottom brackets isn't a bearing race, it's just a stabilizer for the nds end of the cartridge so having it stick out a bit isn't a problem. However, changing the bottom bracket shouldn't upset all of the gearing. Having to do minor trim to the front derailleur's limit screws and cable tension should be all that is needed, if that. It should have no effect on rear shifting.

Are you sure your ordered the correct spindle length for your replacement bottom bracket? Installing a triple length spindle instead of a double, or vice-versa would throw the front shifting off quite a bit.

I would adjust the front derailleur after changing the bottom bracket as a small difference could show up in the shifting.

As far as the BB sticking out on the left side, it used to be that it would stick out and one would install a locknut. But, that was with adjusting cones. It isn't as big of a deal when using cartridges, so I think they normally end up flush. But, I wouldn't worry about it as long as all is tight, and the cranks fit ok.

When the crank arms pass the chainstays, do they appear to be the same distance on both sides?

Cannot comment on Power Spline issues, but slight limit and indexing adjustments may be needed with any component swap, if due to nothing other than manufacturing variations/tolerances.

That you couldn't get the NDS cup fully seated probably means your chainline has been shifted outboard, which means you need to re-adjust your derailleurs.

Probably best to try and figure out why you couldn't get the cup fully seated, though. I'd remove the bottom bracket and clean out the threads in the shell with a stiff wire brush, or better yet, chase them with a tap.

Thanks HillRider - I just went with the info provided by Halfords in store - i.e. 118x68. The part codes are slightly different, though spindle length on both is 118mm. The part I got is the 118 x 68E/73 AL Cup. The original just has '118/68 no spacer' on the side. Does that sound right? TY.

Thanks Clifford , yeah it's fairly symmetrical. I did give everything a good clean so maybe I've inadvertently moved something. Think I might just re-do it all tomorrow and see what happens...

Thanks dsabrantjr!

Thanks John - yes, going to strip it all down and start again tomorrow. Everything was properly clean and de-greased (used disc cleaner and air). I want to compare old v new again anyway just to make sure - might put the old one on again and see how it looks.

It looks like you got a 73mm BB to replace the original 68mm BB. The "68E/73" means that it fits a 68mm bottom bracket with an E-type derailleur or a 73mm bottom bracket. In that case you should have installed a 2.5mm spacer on the drive side. Without that spacer, the bottom bracket and cransket will be shifted 2.5mm toward the non-drive side and cause the problems you describe.

Hi dsaul.

Yep. Think you're right. I'll order the spacer. I'm hoping there are instructions on how to insert it - is it straightforward enough?

I put the old one back on today to see how it looked and it was def. more flush on the nds but much the same as the new unit on the ds, so I'm wondering why it would affect the front derailleur so much.

Pain in the proverbial. But will know better next time and will not be swayed by Amazon prime's promise to 'get it tomorrow' again!

Thanks all for very helpful comments.

boz

The spacer goes onto the bottom bracket cartridge before it is inserted into the frame, so it sits between the drive side of the bottom bracket shell and the flange on the bottom bracket cartridge. Most 73mm bottom brackets come with a spacer to install them in a 68mm shell, but yours was intended for an E-type front derailleur, so perhaps one was not included because the E-type bracket takes the place of the spacer. I have a stack of unused spacers that were acquired with bottom brackets over the years. I suspect that your local bike shop has plenty of them laying around.

Thanks again dsaul - will let you know how I go.

Hi
I bought 2.5mm spacers but they didn't seem to fit. I've just installed the BB without them and had a crack at calibrating the front and rear derallieurs and all seems to be working fine now, after a bit of fiddling of course. Thanks again all for contributions.