[Closed] Bottom bracket cup keeps threading.

If it was me, I'd take a Stanley* knife round the threads, both in the frame and that manky BB.

The threads on the BB looked goosed anyway. See how the pitch changes?

* other brands are available

Go to a bike shop and pay a little for a fresh cut through. That paint is messing up your start. Or find an old steel square taper BB and cut In Very carefully With that. Or get a Stanley knife and clean up that paint from initial threads and then cut in with steel BB. Frame needs a little TLC but that BB looks a bit vague in thread.

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As above, that BB thread looks mangled.

That's a brand new as it come from cotic frame.

Should I just take it to a shop and get them to chase the threads clean.

Sure you are going the right way? Looks just like mine when I got my left and right hand threads messed up! I was impressed the bike shop could chase the BB threads as I'd done a pretty good job.

Aye, you've gubbed that. Go to a shop +1.

That was a brand new BB cup that I was trying to fit.

Surely the damage to the frame threads wouldn't have been caused by trying to fit two softer BB cups.

If you look closely at the frame it looks like the drive side threads are sat quite deep into the shell. Almost as though it needs facing more

The purpose of facing is to ensure the threads are perpendicular to the face, it'll only be faced until that is achieved.

How deep the threads start is pretty irrelevant. The fact the BB cup is alloy, and frame steel, any poor installation is gonna show on the cup.

Top tip (as you won't take it to a shop, as we've seen before) - offer cup to face and gently turn it the wrong way, when you hear and feel the click, the threads are aligned, gently turn the correct way.

I do the turn wrong way real gentle, feel the slight click in the turn correct way too.

If the frame's brand new, i'd contact the supplier before doing anything else, they may well replace it.

For the sake of £10-15 i'd let a bike shop fit it. From looking at your BB cup you must have used quite a bit of force to get it that far into the frame cross-theaded!
Frame thread issues aside I think you've maybe been a bit heavy handed to not notice it going in wonky yet get it that far into the frame (no offence meant).
I doubt very much you'll have caused any damage to the frame as its steel and the cup is aluminium.

That's how I fit the bottom bracket all the time ..... Turn wrong way gently until you feel a click and then gently turn it into the frame.

I did it this way on this frame and it started to go in ok but then went tight so I backed it off then tried again and it went a bit more.

Both brand new cups I tried ended up threaded the same way.

Cotic chase and face the frames before sending it out.

I'm going to send it to my local shop.

Cotic chase and face the frames before sending it out.

Why is there a load of paint in the threads then?

Renton, you have on here for years, not got an old school steel square taper BB on a murky spare parts bin. Plenty of copper slip and sorted.

I'm guessing this means chasing and facing?

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In my experience that paint indicates it has not been chased.
You say the BB cup is new, crikey it’s looks totally brutalised. Fitting marks all gouged both ways on outside and filth all in the cross cut threads.

If you look closely at the blown up photo of the BB. You can see the threads up to the circled area are damaged. The profile of the thread pitch is different from the thread go the left.

You have gone in slightly off. I'm assuming the thread has tightened until it jammed because of damage to the drive of the cup.

That's quite bad damage. As it's a new frame leave it (which I know is easier said than done) and get the threads chased/cleaned. Otherwise your new frame will be useless.

Or, also likely, the frame is painted, paint is left on the chamfer, then it's threaded and chased. There is quite often paint left on here, as neither the facing nor chasing will remove anything from the lead in chamfer.

Some of that paint is then carried in by rentons BB not being started square.

You say the BB cup is new, crikey it’s looks totally brutalised. Fitting marks all gouged both ways on outside and filth all in the cross cut threads.

Agreed, looks anything but a new cup.

Bike shop.

Bike shop it is !

I can always install cups half or most of the way in by hand on every frame I've had before grabbing the wrench.
That bb cup is now buggered, frame threads look okay but the facing could be better. I always face my own frames and they've always needed it.

I wouldn't touch it if you brought it in to my workshop, it's a brand new frame and it's thread is damaged (clear as day in the first pic). If I tried line-tapping it,the onus is on me if it makes the damage worse,i'd recommend you to send it back.

Interestingly there are a couple of other people on the Facebook Cotic owner group that have had the same issue on the same frame and on the same side.

Had similar on. An old (new at the time) soul in the shop.

Ran the var chaser through and it sorted it out .

The first photo in particular looks alot worse than I had though.

Isn't the first pic just a trick of the light, seems fine on the fourth pic.
If it's been chased by cotic before being packed up I can't see how its happened.

4th pic doesn't look much better

3rd pic looks ok if your squinting.

I think it is how the light is catching it to be honest.

In the other pictures the threads look ok and not damaged.

I can't see a defined start of the thread though as it may still be covered in paint. Maybe this is why it's going in wrong

I made sure that it was parallel to the frame when screwing it in and this still happened.

I've pinged cotic an email to ask their advice too.

That's screwed.

Speak to Cotic then take it to a shop and get the thread chased. More than likely the edge of the first thread has distorted meaning it will screw in initially and then cross thread. Thankfully its not been screwed in fully.

The bb is dead. Get a new one

Click on the first pic and enlarge it.
That's ****ed.
The first 3 or 4 threads in the bottom left of the picture look particularly bad.

I had a similar issue on my Cotic, not recently mind. I took it to a shop and have had no issues subsequently with changing the BB.

Question: would an aluminium BB cup do that damage to a steel thread ?

Doubt it, but you should be able to get the cup in by a few full turns before needing tools. Maybe use a pick or little wire brush to clean the paint off the initial threads so you can see clearly where the threads start.

I agree that first pic has the threads absolutely gubbed

Question: would an aluminium BB cup do that damage to a steel thread ?

Well, from the looks of the 'new' bottom bracket cup that appears to have been fitted with a lump hammer and cold chisel, I'd say yes! 😲

Anything can be damaged if you try hard enough.

You say you've tried 2 cups... you've mentioned a new cup, and you've taken photos of a cup that is not new.

There might be a genuine QC issue, but you're not helping yourself by potentially damaging the frame threads with a minging old BB cup.

What have you actually done? it's easily fixable whatever it is - I bought a second hand rocket frame off here with the BB seized so badly that I ended up shearing off the outer cup, even that was only £15 or so at a bike shop to carefully remove the remains and re-tap the thread.

That is genuinely a brand new cup.

I used a bit of the green grease that comes on new BB and rubbed some of that around the threads before screwing in the cup.

The cup went in ok to start with but as it got tighter I backed off a bit and then went again. It all looked parallel until when it got to torque the cup in and then you could see it was off.

I fully appreciate that the cup looks battered. My BB tool although being a genuine Shimano one isnt great but work. It just leaves marks on the cup.

I'm guessing that what is on the threads is the grease and whatever was in the threads on the frame.

Other side went in fine.

Two other folk have had issues with the drive side cup in their new BFe max frames. So not sure if a QC issues.

I've emailed Cy to see what he says.

It all looked parallel until when it got to torque the cup in and then you could see it was off

That just doesn't add up, especially given how you've basically used the BB shell as a tap to re thread the BB cup.

I've got no reason to make it up.

As it stands I've got a £550 frame that I can't use.

I'm not saying you've made it up, but that what you said doesn't make sense.

The cup suddenly gets cross threaded after you've screwed it mostly in?

Just a thought.

If you inspect the BB shell, is there any possibility that someone has accidentally used the wrong thread chaser in that side, then realised their mistake and tried to fix it by using the correct one. That could mangle up the threads somewhat if it was not run through a few times to sort it.

Seen it done. (Not by me 🙂 )

Shirley that BB wasn’t new when you started this 🤔

That said I don’t believe that’s the primary issue.

I have had threads chased, shell faced pre shipping of frame and by my LBS.

On occasion the threads in the BB shell have almost been sharp so when a BB cup is threaded in its literally recut the BB threads - most obvious with anodised cups.

That said I don’t believe that’s the issue either.

It’s looking cross threaded to me 😕

It’s looking cross threaded to me

Do you mean the frame and if so do you think it's likely it was like that before I started ?

You might have been better off just talking to Cotic before you started this thread...
Better still if you'd not posted pics of the BB.