Bottom bracket fitting problems, help needed

[ishaw]

The BB I have has twice as much thread as the one above. No reason that should be an issue but it's certainly a difference.

I guess I'm back in the market for a 73 X 113.

 

[Frankenorange]

Every now and again there is going to be a cup thread that is at the upper end of a pass and it is going to be too tight in a BB.
Would be interesting to put the cup up on a shadowgraph/profile projector and check the profile of the thread. Maybe something happened with the tooling and a bunch came out a bit goofy and it isn't actually a pass.

 

[whojammyflip]

I'm trying to fit a UN55 in a Trek 950 OX II frame, and experiencing the same. I was googling for solutions to this. Sounds like a different bottom bracket is required or getting it tapped is the solution. I can try forcing it in, but the threads on the NDS cup were getting damaged and the spindle started to feel rough as if there was stress being applied to the bearings. Its interesting that its a combination of a Trek frame and UN BB.

 

[Uncle Grumpy]

...... so why am I having such problems fitting the BB on the frame I need it to fit in (trek 930 steel)?

I'm trying to fit a UN55 in a Trek 950 OX II frame, and experiencing the same.

It's okay, I'll show myself out.

 

[whojammyflip]

The BB I have has twice as much thread as the one above. No reason that should be an issue but it's certainly a difference.

I guess I'm back in the market for a 73 X 113.

What was the solution in the end for you, please?

 

[whojammyflip]

https://www.webbline.co.uk/shop/bottom-bracket-taps-bsa-pair/https://www.merlincycles.com/cyclus-bsa-bottom-bracket-tap-230298.html
What is it about £50 for a set.
Up to you whether it's worth it.
May be cheaper to visit the lbs for this one.
Or simply use a different BB.

Webbline looks like a useful shop.

 

[whojammyflip]

So I bought the BSA taps from Webbline and the problem is solved. A couple of tea spoons of gunk came out of the threads, a mix of dirt, rust and the cutting oil. I think these are top value at 50 quid. I could put both sides of the bottom bracket in by hand up until they meet, and the left hand cup has some white sealant in it which is a bit stiff and needed the BB tool to see it home. But the binding of the spindle has now gone.