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Old 08-03-10, 09:03 PM   #1
jameswelle
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Is this frame destroyed?

A friend gave me a 2002 Bianchi SL Lite Alloy that hadn't been ridden in a while and needed some work. The drive-side cup of the bottom bracket was very hard to remove from the frame. I had to use a 4ft long pipe to get enough torque to get it out.

The threads look like they may be destroyed. It looks like the metal from the shell and the metal from the cup fused together or something? Is that what happened?

The cup says "Campagnolo 1.370 x 24 TPI". Is the frame destroyed or is there anything a shop can do to salvage it?







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Old 08-03-10, 09:09 PM   #2
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To me it looks like there is just a bunch of debris in the threads. The BB looks like it has aluminum threads but even if it's steel, remember the male threads will usually fail first. Clean the threads out carefully.
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Old 08-03-10, 09:11 PM   #3
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I'd have to say that the metal pulled out in the first part of the threading pretty much tells the story. It's toast as far as fitting in a same thread size BB. You can chase out the threads but that won't replace metal that is already gone. It'll just clean up what is smeared into the way and leave you with half height or less threads with plateau tops.

It leaves you with two options as far as I can see. First is to have the BB shell re-threaded to a BB style that uses a larger thread size. But unless it is larger enough it'll just mess up the threads again. On top of that I'm sort of thinking without checking that this is already the much suggested larger Italian threading that folks suggest as a fix for ruined English size threading. If so then that won't help you at all. Second, or perhaps the only option, is to use a threadless BB that pressure locks into place thanks to tapered cones. Velo Orange sells such a beast.
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Old 08-03-10, 09:14 PM   #4
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To me it looks like there is just a bunch of debris in the threads. The BB looks like it has aluminum threads but even if it's steel, remember the male threads will usually fail first. Clean the threads out carefully.

Check out the smeared metal embedded in the threads of the BB. That's metal torn away from the crests of the shell threading that was holding the BB in place. It's pretty much reamed it all away. Also the stringy looking things you see in the picture of the BB shell is actual thread metal that was sheared off. Much damage has been done.
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Old 08-04-10, 07:21 AM   #5
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What would cause this? Would the male threads on the cup and the female threads on the shell fuse together if the bottom bracket was never serviced and removed?
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Old 08-04-10, 07:23 AM   #6
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The cup appears to be aluminium; I'd hazard some corrosion has preceded some serious galling.
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Old 08-04-10, 07:32 AM   #7
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I would try chasing the threads and using loc-tite to help hold the new BB in place.

A friend who used to work at a beach-side shop with lots of seized BBs suggests using some sort of impact wrench in order to salvage the BB shell when removing a seized bottom bracket. He said the heat generated from all the torque of slowly spinning it out of the corrosion or rust usually pulls the threads out of the shell, whereas quick bursts of energy from the impact wrench can avoid overheating and stripping.
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Old 08-04-10, 07:44 AM   #8
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All you need to do is chase the threads and get a new BB. There appears to be plenty of turns of good thread left near the face. It only take about 4 turns to get all the strength from a thread.

Next time, use grease of anti-sieze on the threads and be sure that the shell has a drain hole, so water can run out.
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Old 08-04-10, 08:23 AM   #9
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OK, I will take it to a shop here and see if they think the threads can be salvaged at all.

In order to prevent this on future bikes, what should I do? Was it caused by water getting into the shell, corrosion starting, and then galling (basically the two metals fusing) occurred?

If you install a bottom bracket correctly, and then never take it out or re-grease it or anything for 10 years, would you expect this to happen or would it be fine?
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Old 08-04-10, 08:25 AM   #10
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Quote:
Originally Posted by BCRider View Post
Check out the smeared metal embedded in the threads of the BB. That's metal torn away from the crests of the shell threading that was holding the BB in place. It's pretty much reamed it all away. Also the stringy looking things you see in the picture of the BB shell is actual thread metal that was sheared off. Much damage has been done.
I could be wrong but to my eye the bb collar looks aluminum and the bb in the frame looks steel, although it is on the thick side if it's steel.

Could it be that the frame required an English BB and someone tried to force in an Italian one?

At any rate, I don't think we can recklessly assume the debris comes from the threads in the frame.

Last edited by garage sale GT; 08-04-10 at 08:35 AM.
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Old 08-04-10, 08:52 AM   #11
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As already noted, grease or antisieze on the threads. Leaving a BB in place for 10 years is not wise, particularly if the bike is ridden in the wet. Yearly maintenance would then be wise.
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Old 08-04-10, 10:38 AM   #12
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Does galling basically mean that the two metals fuse together?

Does it happen only because the aluminum started to corrode due to water? Or would it happen even if the threads were dry?
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Old 08-04-10, 11:18 AM   #13
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Galling takes place during tightening or loosening. You could also have galvanic corrosion involved.

http://metals.about.com/library/bldef-Galling.htm

http://en.wikipedia.org/wiki/Galvanic_corrosion
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Old 08-04-10, 11:55 AM   #14
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Originally Posted by jameswelle View Post
What would cause this? Would the male threads on the cup and the female threads on the shell fuse together if the bottom bracket was never serviced and removed?
It's most likely a result of electrolytic corrosion. This is always a risk when dissimilar metals come into contact. Using an anti-seize compound on the threads would likely have prevented this.

As the shell was originally tapped as English, it is likely possible for it to be retapped to Italian dimensions. Otherwise, a threadless cartridge as suggested above would also work.
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Old 08-04-10, 12:03 PM   #15
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Yeah, I am confused on the threading on this bottom bracket.

It says 1.370 x 24 which means the threads are English-sized, right?

But I had to turn the drive-side to the right/clockwise to remove it and the non-drive side left/counter-clockwise, so that makes it seem like it is Italian threaded, but in reverse of what is listed here: http://www.sheldonbrown.com/gloss_ta-o.html#threading

Bizarre.
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Old 08-04-10, 12:05 PM   #16
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The 1.370 x 24 TPI indicates that it's an English bottom bracket. You should verify that it has a 68 mm width. If it does , then there are there are threadless bottom brackets available.

http://www.velo-orange.com/grcruthbobr.html
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Old 08-04-10, 12:05 PM   #17
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yes, But, Your auto focus doesn't give a clear picture of the BB shell threads on the Near side,

If it were a Film camera ('prosumer' one) I'd say stop it down to a very small aperture, (higher f number), to increase the depth of field,
slow down the shutter speed to get the exposure right, then take another picture..

But from the condition of the in focus Far side, ant that the threads in the BBshell that would contact that point, are OK, Ill say:

chase the threads, that is use the BB threading tool to clean up the existing threads , rather than cut new ones , then buy a new BB,
this time grease , or use anti-seize and buy the proper installation tool for the new BB.

You will not need threadlock [which wont work with greased surfaces, anyhow] if you get the Cartridge BB tight enough in the frame,
with the proper Ring wrench , for that BB you need : http://www.parktool.com/products/det...5&item=BBT%2D4

There is a different Version of that same Campag BB which is intrenally splines, It uses the same tool as Campag's Cassette lockrings for the wheel.

NB there are 2 Square taper standards so You need to get the right one JIS, Japan, ' and ISO, European parts.

though some crossover is possible, ex: I have an 80's Campag Mtb Crankset and it is functionally interchangeable
with Shimano's M730.

Last edited by fietsbob; 08-04-10 at 12:37 PM.
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Old 08-04-10, 12:28 PM   #18
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So it is an English bottom bracket but it is threaded in reverse of what is normal?

i.e. the fixed cup is right-threaded and the adjustable cup is left-threaded.
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Old 08-04-10, 12:31 PM   #19
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the Right, drive side in the British pattern is always left hand threaded on the right side, Right hand threaded on the left side.
the BB axle turning while you ride, so the cups in the frame tends to stay tight that way ..

SAT test pointer , remember the bearing ball rotates in reverse of the 2 parts it contacts..

Last edited by fietsbob; 08-04-10 at 12:35 PM.
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Old 08-04-10, 12:46 PM   #20
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If the threads are toast, you can try out a Mavic BB instead. that does not use the threads on a BB but uses angled retainer rings that tighten against bevels cut into the faces of the BB shell instead. They were sold in the 80's and 90's, but lots of them still pop up at ebay for auction. You will have to find a bike shop that has the correct Mavic cutting tool(s) to cut the needed bevels on your BB faces. Look to spend about a hundred bucks though, for an NOS Mavic BB....plus the cost of the BB face beveling at the bike shop. Could be worth it if your frame is a good one, as the Mavic BB is high quality. I beleive Velo Orange also sold their own version of the BB, and could be a cost effective alternative if you can find them.

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Old 08-04-10, 01:22 PM   #21
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Sorry if I am being dense, but I'm still confused on the threading.

The fixed/drive-side cup says "Right Lock" with an arrow pointing counter-clockwise. To remove it, I had to turn it clockwise. Which means that pedaling would loosen the threads.

So the drive-side cup is right-hand threaded or Italian threaded, right?

The adjustable/non-drive-side cup says "Left Lock" with an arrow pointing clockwise. To remove it, I had to turn it counter-clockwise. Which also means that pedaling would loosen the threads.

So the non-drive side cup is left-hand threaded, right?

That doesn't match any entries in the table on Sheldon Brown's site: http://www.sheldonbrown.com/gloss_ta-o.html#threading

The only entry it partially matches is English, but with the threading reversed on each side.
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Old 08-04-10, 02:13 PM   #22
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Precession would make the effect of pedaling work opposite of the way you think it would. If you had to turn the drive side clockwise to loosen, it is left hand threaded. It is an ISO bottom bracket, and from the picture , it looks like a Campy AC-H. I would try to chase the threads to see what the real damage looks like. My gut is telling me that it will be fine with a new bb installed. Just make sure you pull it once a year and regrease the threads. The old bb was stuck due to galvanic corrosion, which could have been avoided by renewing the grease (or anti-seize) in those threads once a year or so.
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Old 08-04-10, 02:19 PM   #23
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The threading is normal English. Left handed on the right side and right handed on the left. Clockwise to remove is left-handed.

Last edited by DaveSSS; 08-04-10 at 02:55 PM.
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Old 08-04-10, 04:12 PM   #24
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Got it! Thanks for all the help. It sounds like if the threads can't be chased, I can always expand to Italian threading then.
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Old 08-04-10, 04:29 PM   #25
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Got it! Thanks for all the help. It sounds like if the threads can't be chased, I can always expand to Italian threading then.
While I've heard of that being done, it really requires boring the BB shell to a slightly larger diameter first. Just cramming a right handed Italian tap into a left hand threaded BB isn't a great idea. The minor diamter of the thread should be bored into the BB shell first. Also, the BB would be 2mm too narrow (68mm rather than 70mm) and need a 1mm shim on the right side, at the minimum.
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