Author Topic: Bottom bracket thread wasted ... new frame?  (Read 655 times)

Bottom bracket thread wasted ... new frame?
« on: December 04, 2017, 01:53:46 pm »
For some time I noticed that my gears wouldn't change as I set them up.  On closer inspection I noticed my bottom bracket not properly attached to the frame. I took it apart and was about to get a new bottom bracket, when I saw that the thread on the frame had wasted. 
In the pics you see that the thread on the bottom bracket itself is still pretty good

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but the thread on the frame is "run down" on the front

,

- evidently where I would be pushing into the pedal - whilst the back is still reasonably OK

, .

I tried as plumber's approach but to little avail.

, .

The bracket has come loose again and is stopped from falling out by the crank attached on the other side.

I know that with some effort there is an option to insert a coil into the thread, but that would mean that the bottom-bracket needed a smaller diameter.

BTW, when I took the bike apart a few years ago, I saw it must have been one of those last British manufactured Raleigh Randonneur diamond shaped steel-frames (1975 or thereabouts). 

Anyway, never mind the current rust on the bike, has anyone an idea how I can keep my frame?  Or do I have to get a new one?

Thanks for your thoughts.
Stefan

Eine Sache ist nur verloren, wenn man sie aufgibt. (Freiherr von Stein)

Re: Bottom bracket thread wasted ... new frame?
« Reply #1 on: December 04, 2017, 02:01:32 pm »
I've rescued (for some value of rescue) a frame from much worse than that.

You have two options:
Tange Prestige BB

Epoxy metal.

You've lost very little threading there. I think wire brush out the rust very thoroughly. Inspect for cracks. Reinsert BB and see how loose it feels (mine was so loose there was a gap all round, I'd stretched the BB shell).  I suspect just a little.

Now get some decent epoxy metal. Make it up, smear it into the threads, just a bit. You don't want fast set, and you want it to have the consistency of old linseed oil putty.
Now oil your BB threads - this is to stop it sticking to the epoxy. Very carefully screw it in to the bb and screw out. This is to 'recut' the threads over the epoxy. Let the epoxy fully set and try it. It might now be a really hard fit, you can always sand out the epoxy it it is too hard.
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Re: Bottom bracket thread wasted ... new frame?
« Reply #2 on: December 04, 2017, 02:33:25 pm »
Thanks very much for that advice.  I'll have a go.

When I put the white tape on I needed quite a bit. The gap felt like 1 mm either side, but it might have been less, as the "feeling" for this depends on experience, and I have little of this.

Thanks again - will probably be after Christmas, before I report back.

Have a good one!
Stefan
Eine Sache ist nur verloren, wenn man sie aufgibt. (Freiherr von Stein)

citoyen

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Re: Bottom bracket thread wasted ... new frame?
« Reply #3 on: December 04, 2017, 02:47:58 pm »
Don't worry. If you're looking for an excuse to buy a new bike, we're behind you all the way.  :thumbsup:

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Re: Bottom bracket thread wasted ... new frame?
« Reply #4 on: December 04, 2017, 02:49:05 pm »
My Dawes Galaxy has had this problem for more than 10 years.

I have had great success with YST threadless bottom brackets.  Just make sure they are screwed up tightly.

My frame could do with a respray now, and I'm considering whether it's worth getting a new shell at the same time.

Blodwyn Pig

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Re: Bottom bracket thread wasted ... new frame?
« Reply #5 on: December 04, 2017, 08:01:54 pm »
if its a last ditch attempt, then fit with all methods mentioned, and when as tight as can be drill 2 small hole through shell (or even do this before refitting) then just into the thread of the bb unit, and tap with a thread and insert 2 locking grub screws.

Re: Bottom bracket thread wasted ... new frame?
« Reply #6 on: December 04, 2017, 08:06:14 pm »
Well, I've ordereed a YST threadless BB. Will see how this goes, when it arrives on Thursday, I hope.
Eine Sache ist nur verloren, wenn man sie aufgibt. (Freiherr von Stein)

Re: Bottom bracket thread wasted ... new frame?
« Reply #7 on: December 04, 2017, 09:50:20 pm »
If the frame is worth it, and steel, traditional solutions from frame builders include running brass into the threads and retapping, and cut-and-close. The latter involves cutting across the BB shell from side to side (underneath), closing it up, and brazing the gap. This creates a marginally-smaller shell into which a new thread can be cut.

However, a threadless BB looks good for your situation, unless you're contemplating a respray.

Re: Bottom bracket thread wasted ... new frame?
« Reply #8 on: December 11, 2017, 09:02:02 pm »
Current threadless square-taper BBs [YST] look and feel better quality than in the past. Ruby Holdsworth now has one - though done up very tight it loosened within a week. Second attempt with lotsa threadlock seems to be holding...not sure I'll tackle PBP on it again though...

Re: Bottom bracket thread wasted ... new frame?
« Reply #9 on: December 13, 2017, 10:29:00 pm »
The other framebuilder option (short of a replacement BB shell) is ream & sleeve - ream out the old threads, braze in a steel liner, then cut threads in that. Argos did one of my old bikes like that, and it was as new for the 8 or 10 years I was riding it.

Traditional threadless BBs relied on a chamfer cut in the outside edge of the BB shell to take vertical loads, and if there isn't one, they'll move, at least until the shell and lockrings wear to match.
The other option is the Velo Orange internal expanding BB. This should be more proof against movement, but I'd probably want to have it out and regreased/anti seized a fair bit more frequently than I'd look at a UNxx.

Re: Bottom bracket thread wasted ... new frame?
« Reply #10 on: December 14, 2017, 11:23:17 am »
About 6 years ago when the BB shell failed on my old Galaxy, which I only use as a winter and town bike, I fitted a cheap Acor threadless one. This did job okay but following a forum thread I decided to upgrade to a more expensive and was lead to believe a much better, Velo Orange one. I went to great lengths to fit it as per the video instructions using Locktite. It lasted less than a month before it started to rotate within the shell. I put the old Acor one back and have not had a problem since. Velo Orange did refund my money.

Last year when the BB on my Super Galaxy, which I use for my cycle camping, started to show signs of play, I got Argos Racing to do their shell repair. This cost around £80 but well worth it for a more permanent repair. There was no damage to paintwork and they did it in less than a week. This method would definitely be my recommendation.


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Re: Bottom bracket thread wasted ... new frame?
« Reply #11 on: December 15, 2017, 01:18:01 pm »
I feel your pain :'(

My 30 year old frame has rusted bb threads too, I`ve tried a couple of bottom brackets that screw into themselves and clamp into the bottom bracket shell, the first alloy one lasted 100km, latest steel one is ok. I think the problem is that once the bottom bracket thread rusts away it effectively makes the bottom bracket shell very slightly larger so any replacement cups aren`t a good fit and will eventually start to move.

I don`t trust the frame now, really it`s a bodge job and if it`s rusty in one place it`s rusty elsewhere.

It`s spurred me on to achieve N+2. One bike to replace this one and another frame to prevent all the parts on the rusted out one going to waste :thumbsup:

A new steel frame cost a few hundred quid, it`s a much better design than my old one, better quality too and if it lasts another 30 years it`s a bargain.

My rusty old Woodrup is leaning against the wall opposite me, I can just about remember all those epic rides :)

Re: Bottom bracket thread wasted ... new frame?
« Reply #12 on: Yesterday at 11:55:02 am »
I'm tempted to have Argos ream and sleeve the Raleigh Twenty one day to eliminate the Raleigh BB threading.  They can also mill the shell down to 68mm from the super-wide 78mm.  I have no idea why Raleigh made it so wide, because it actively ruins the chainline (the chainring is too far out, so the chain fouls the chainstay if you try to run it straight) and there is plenty of meat to be cut off at either side of the shell.

Sometimes Raleigh just did stupid things.

The ream-and-sleeve is £90 but I don't know whether it is done without ruining the paint, which would cost you another £150 plus decals.
Never tell me the odds.

Re: Bottom bracket thread wasted ... new frame?
« Reply #13 on: Yesterday at 04:09:17 pm »
The ream-and-sleeve is £90 but I don't know whether it is done without ruining the paint, which would cost you another £150 plus decals.

They did my repair without any damaged to the paintwork. If you are having the shell milled down there will be some bare metal that will need a retouch of some kind.
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