the BB in my Kaffenback was feeling a little grouchy, no problem thinks I, I have a spare so 15 minute job to replace…how wrong I was…

So, first the BB (a standard Tiagra level external job, installed by PX when new) was very stiff to come out both sides. There was a touch of rust inside the BB shell (steel frame so not wholey unexpected) so I cleared this out and also cleared out any muck from the threads. Next I applied a thin smear of grease around the now clean threads and on the threads of a new 105 BB. I double checked I was installing on the correct side and also that I was turning the right way. And yet, I could not get the new cups into the frame. I’m always very hesitant when installing BB’s and will not get the spanners out until it’s pretty much all the way in, if I can’t get it in with just my fingers I back off and start again.

So people of STW, what am I doing wrong? It the right size of BB (well, assuming the right one was in when I bought it), I’ve triple checked I’m installing the right side and turning the right way and the threads seem clean. Any ideas?

i believe all shimano ht 2 style cups are the same sizes so I’d get the threads
chased out as you said you had “trouble” getting the Tiagra out.

It might need a tap running through to properly clear out the threads. Not generally a tool the average DIYer has to hand unfortunately but should be a very quick job for your LBS.

The BB you are trying to fit is the correct thread is it ? ie English and not Italian ?

ISO/English or BSA 1.37 in x 24 TPI
Italian 36 mm x 24 TPI
French 35 mm x 1 mm

it should say on the BB cup.

run tools through there (to cut threads and face) with cutting fluid, degrease and then install the BB with a smear of grease on the threads

It’s probably safe to safe neither the frame or bb will be French lol

Heh, i had something similar the other week.

Wouldn’t bite the thread for toffee.

Then I realised Shimano had reversed the cups on my new BB – so the side with the spacer was on the opposite side to the previous BB. I was checking them against each other assuming they were the same.

Felt a reet fool. But figured it out after 5 minutes of good beard rubbing.

“The side with the spacer”?

OP, there’s always the possibilty that the original Tiagra had benn installed squint.

If the bb cups were either Italian or French you wouldn’t be able to get them anywhere near going in!

Get into the shell threads with a wire brush, the rust in there will have the effect of making the threads tighter the further you go in with the BB.

1) Consider cleaning the threads as suggested above. Put the old ones in and out a couple of times

2) Have a look at the bearing threads. My Ultegras have a distinct line around the circumference where now you can see paint(?) and now you can’t
The paint is nearer the outboard side. A spanner works for me at this point

+1 on wire brush and get the old one moving freely first, then copper slip the new one before installation

Good advice, thanks all.

BB is definitely a BSA threaded style and both new and old BB are the same size.

I suspected it may need a chasing but will attack it with a wire brush first if only to avoid the hassle of taking it to my LBS.

On my inbred, built by on-one, various fasteners were either too tight or too lose. The rear cassette was a proper ball ache to get off, whilst the cranks fell off all by themselves. Was thinking of buying them a torque wrench for Christmas.

So wouldn’t be surprised if the original cups were poorly installed, without grease, hence causing the rust. Saying that when I changed mine on tfe inbred the new ones went in fine.

If you don’t mind a bit of DIY/bodging…

If you had an old steel cup and cone BB knocking around, grinding a few slots across the threads of the cups would give you a improvised tap. Not as good as a proper one obviously but better than screwing in an alloy BB with no cutouts.

Worth a try if you have the gear maybe?

“The side with the spacer”?

The side that comes with the internal plastic BB Spacer attached to it.

Now I think about it, I guess that spacer could be removed and be “stuck” to either side, I never tried.

just get it chased out, removes all doubt and makes the job a piece of piss. if its rusty now, it’ll only get worse so next time you replace a bb it’ll be a pain again. Do it right now and save yourself more hassle.

Photo ^^ shows the paint(?) that I referred to, looking at the photo, is it threadlock?

@plyphon. The tube is removable and can be attached to either cup. The cups themselves will be marked left and right or drive and non drive side. The cups may also have arrows on them telling you which way to tighten or loosen them. The drive side or right side is a left hand thread. Just in case that’s not clear, right is on the right as you sit on the bike, facing forwards.

@timba, yes, it’s threadlock.

In the unlikely event anyone is even slightly interested in the outcome of this, I attacked the frame BB threads with a wire brush after soaking it in GT85 for 24 hours. A lot of muck came out and the BB went in with little or no force at all.

Job done, and all for the cost of a wire brush that I will undoubtedly use again in the future.