Square taper bottom bracket problems (seized/bent cup)

[NickNick]

I'm currently running an Ammaco XRS700, crap bike, but it was free and got me into riding again so shouldn't complain.

Its got the old fashioned square taper bottom bracket which had really stiffened up a few months back. On close inspection, the drive side cup was not sitting flush against the shell, approx half the cup is flush but the rest of it has a 1-2mm gap with the shell. I'd ideally like to take it out and replace with HollowtechII so I can use my new chainset with this bike.

My worry is that its cross threaded and that in process of taking it out I would destroy the thread. From what I've been able to find out, if that happens to a heat treated aluminium frame its game over as it would cost more to fix than frame is worth.

I had a crack at removing it anyway but its completely stuck. I've got a good LBS with a great old school mechanic, had a chat with him and he was of the opinion that there was a fairly good chance it was not cross threaded and that it was an issue with the cup splitting iirc and in which case only the first section of the thread would be damaged. However there would be no guarantee and until he has a go at it there's no way of knowing if the frame is a write off or not.

I really can't afford more than a day of down time with the bike at the moment as I use it to commute to jobs all over the place and between the money & extra time involved with public transport... So I've been doing a bodge to keep it running until I can get a spare frame and keep potential downtime to a minimum.

I've been putting new bearing cages in every couple 3-4weeks, to have non drive side cup tight enough to not have ridiculous levels of play, it has to be in so far that the lock nut won't fit on it. Of course this causes it to over tighten over time, I loosen it up after every ride but on the longer rides its still starting to mess up the cages by time I get back.

I've by chance found a new frame on ebay that I could both afford and was close enough to collect (will be doing separate thread regarding the new frame).

Do you guys&girls have any thoughts on how I could repair this myself?

Is it worth running it up to the LBS (he quoted £15-£35) to see if he can repair it?

Or should I just scrap it? Even fully functioning its pretty crap, but equally if I can get it sorted for a reasonable price, it would be good to have a spare bike.

PS I will try and get some photos taken when I get back this afternoon if that helps.

 

[overmind]

Is it the fixed cup which is cross threaded (I think this is the one on the drive side) ?

 

[NickNick]

Is it the fixed cup which is cross threaded (I think this is the one on the drive side) ?

I think so, I presume the fixed cup is the one that doesn't have the lock nut on it?

 

[Tim Hall]

You say the cup is completely stuck. Assuming the BB is the cup and cone type, with removable bearings and axle, have you tried Sheldon's nut and bolt method, as outlined on this page (scroll down to Fixed Cup tools). It's a masterpiece of engineering theory and elegance, plus a bit of brute force. I think I used an M16 bolt in place of the 5/8" he suggests.

 

[MichaelW2]

If the BB shell is not accurately faced, then any external style BB will be misaligned. Fit a Shimano style cartridge square taper of reasonable grade and you will have full free riding for many years. The cartridge systems are not affected so much by poor frame alignment and facing.

 

[overmind]

I think so, I presume the fixed cup is the one that doesn't have the lock nut on it?

This is the fixed cup (note: the fixed cup unscrews CLOCKWISE)

This is the adjustable cup.

 

[mjr]

If the BB shell is not accurately faced, then any external style BB will be misaligned. Fit a Shimano style cartridge square taper of reasonable grade and you will have full free riding for many years. The cartridge systems are not affected so much by poor frame alignment and facing.

But to fit a cartridge, you'll need to remove the fixed cup, which is where we came in...

 

[Ajax Bay]

Fit a Shimano style cartridge square taper of reasonable grade

But to fit a cartridge, you'll need to remove the fixed cup, which is where we came in...

And the OP's concern is that removing the extremely well fixed drive side cup will 'screw' the threads. The current BB is not fit for purpose but the OP needs to use the bike daily. I think his best course of action is to buy a (£13-£15) Shimano UN-55 BB or similar (with correct length spindle) and then on a Friday evening, go for it (ie remove the drive side 'fixed' cup, with the help of his LBS (first thing Saturday morning) or with @Tim Hall suggestion (above)). Either the thread will be OK to screw the UN-55 in; or it won't. In the latter case, OP will need a bridging loan of a friend's spare bike, perhaps, pending arrival of the new frame he's spotted.

 

[si_c]

Get the LBS to remove the fixed cup if you're not comfortable doing it yourself. If the worst comes to the worst and it is cross threaded it's not game over as you can get bottom brackets designed for situations like this where they are compression fit.

This will allow you to keep using that frame if the worst comes to the worst.

See this for example.

 

[Illaveago]

It may be an obvious question, but are you undoing the cup in the right direction?

The other thing is if you can remove the cup and find that when you try to replace it it still cross threads you could try doing what I did. I used a new sealed bearing unit and placed the non drive cup fully in first ,using that to centralise the shaft and help align the other bearing cup.

 

[QFour]

According to Mr Brown cup is probably left hand thread. Bit of heat may also help as two dissimilar metals will expand at different rates. You could also try laying bike down and putting plenty of penetrating oil round the threads for a few nights. Good Luck

 

[Ajax Bay]

Bit of heat may also help as two dissimilar metals will expand at different rates.

Have you done this? How did you heat the bottom bracket area without damaging the paintwork?

 

[NickNick]

Thanks for all of the recommendations and sorry about delay in replying, managed to arrange to collect the new ebay purchased frame (old Zertz insert era Specialized Allez in reasonable condition), which around work commitments took up the bulk of the day. Spent from 5pm-midnight swapping things over and dealing with the mandatory snagging issues and desperate runs to LBS to get headset bearing cartridges before they close (just made it on time). By 1am I was test riding my new bike (can't believe how light it is in comparison) so its taken a whole load of pressure off and the fear of being stuck without a bike has rescinded!

Plan is to try to get the old frame's BB dealt with, if I can it gives me a spare bike which would stop breakdowns of the main bike being so stressful!

I've managed to take some pics which show how twisted the cup is. Its definitely the fixed cup and it has somehow ended up like this after a number of months of regular usage (when I first got the bike and gave it a service the fixed cup was definitely flush and has not been removed), I'll then respond to individual points.

angle 1

• NickNick
• 11 Oct 2017

angle 2

• NickNick
• 11 Oct 2017

angle 3

• NickNick
• 11 Oct 2017

(excuse the dirt, last ride involved a lot of canal towpaths, can clean up and take more pics if needed)

I'll have one more go at doing it myself (hate not being able to do a repair myself!) when back from Newhaven and if that fails with take it to LBS.

 

[NickNick]

You say the cup is completely stuck. Assuming the BB is the cup and cone type, with removable bearings and axle, have you tried Sheldon's nut and bolt method, as outlined on this page (scroll down to Fixed Cup tools). It's a masterpiece of engineering theory and elegance, plus a bit of brute force. I think I used an M16 bolt in place of the 5/8" he suggests.

Yes it is and yes I did try that method, however I was making do with with bolts/washers that weren't quit big/strong enough and snapped. Think I will try and find a bolt big enough that I can weld its head to the cup and then use big spanner/breaker bar combo.

If that still doesn't work, I'm thinking it might be worth cutting off the face of the cup with a grinder, then using hack saw blade cut 3-4 notches into the remaining threaded part of the cup (stopping just before I reach the threads) and then hammer/chisel them out.

If the BB shell is not accurately faced, then any external style BB will be misaligned. Fit a Shimano style cartridge square taper of reasonable grade and you will have full free riding for many years. The cartridge systems are not affected so much by poor frame alignment and facing.

Its definitely not an issue with shell facing, once I get it out will be going down the square taper cartridge route for this frame as get to reuse the cranks that came with it.

Get the LBS to remove the fixed cup if you're not comfortable doing it yourself. If the worst comes to the worst and it is cross threaded it's not game over as you can get bottom brackets designed for situations like this where they are compression fit.

This will allow you to keep using that frame if the worst comes to the worst.

See this for example.

Had come across those, have read mixed reports on their reliability and it would have stopped me from using the hollowtechii cranks I'd bought, but now that its just going to be a backup bike. that could be the perfect solution if the threads are dead and again seeing as its square taper, won't need new cranks.

According to Mr Brown cup is probably left hand thread. Bit of heat may also help as two dissimilar metals will expand at different rates. You could also try laying bike down and putting plenty of penetrating oil round the threads for a few nights. Good Luck

Will try taking the blow torch to it, managed to use that method effectively in the past on an old steel framed Raleigh. It will damage the paint but that's not the end of the world, might strip and repaint anyway whilst its just a bare frame as I hate the decals/paint job.

 

[QFour]

Heat will of course wreck the paintwork. How attached are you to this bike frame. Seems like you now have something new to you. If you decide to keep it you may find that getting a bar welded across the bearing cover will certainly make it easier to move. Beats buying special tools. While getting a bar welded on ask them to heat it up for you. Good Luck