Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

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goodlife
Posts: 7
Joined: 19 Sep 2008, 3:11pm

Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

Postby goodlife » 3 Jul 2016, 2:00pm

I built up a Dawes Ultra Galaxy 853 frame a couple of years ago. It was a new model with disc brake mounts, a replacement from Dawes for a ~10yo canti Ultra frame that had rusted badly from a defective paint job.

I felt a bit of play in the cranks a while ago but didn't do anything until just now, I assumed it was the BB (from the original Ultra Galaxy, so ~12 years and 25000 miles old) finally wearing out. When I checked it turned out the BB was loose in the shell and has worn out the drive side thread quite badly, so it won't tighten. I've wound quite a lot of PTFE tape around it and it's fairly tight now, but I don't expect that to last long.

From reading around, it seems the proper way to fix this is a new bottom bracket shell. So:
- is it worth spending money on this frame? It says 853, but I think I saw somewhere only the 3 main tubes are actually 853.
- are there any other satisfactory ways to fix it I could consider?

I'm rather annoyed with myself for not noticing this before it was too late. I like the bike as it is, and hoped it would last me many years.

cheers,

rob.

gerrymcm
Posts: 446
Joined: 30 Oct 2012, 2:52pm

Re: Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

Postby gerrymcm » 3 Jul 2016, 2:29pm

I reckon Bb shells aren't tubing specific so any steel one could be cut/shut and then re-tapped
I've never had this done to a bike but I'm sure others on here will have.
Or
http://www.edinburghbicycle.com/product ... om-bracket
i think a couple of manufacturers make these differing lengths as well.
Or
I think I've read Brucey on here saying that you can effectively epoxy stuff into place and then use heat to free it again in the future. If you went the epoxy route and used a decent BB you could get another good few years out of it.

Simplest is the threadless especially if you can get correct length and you like the bike.

good luck

Valbrona
Posts: 2240
Joined: 7 Feb 2011, 4:49pm

Re: Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

Postby Valbrona » 3 Jul 2016, 5:23pm

Check out the press-fit bottom brackets you get. The square taper ones what go in BB shells with damaged threads.
I should coco.

Brucey
Posts: 35924
Joined: 4 Jan 2012, 6:25pm

Re: Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

Postby Brucey » 3 Jul 2016, 6:32pm

goodlife wrote: ....are there any other satisfactory ways to fix it I could consider?...


you can nearly always fit a BB cup using epoxy resin so that it won't come adrift. It can be removed later using heat, which is OK, because most of the other repair options involve using heat too. If you use a BB system that uses two separate cups (and many do, even though they might be supplied with a loose left cup only, the RH one can often be removed too) then you can replace like-for like and never have to disturb the RH cup again even if the BB you fit wears out or breaks.

However, probably the damage is mostly confined to the bottom and the rear of the BB shell.

I have repaired many such frames using the following method:

1) clean up the threads

2) add individual blobs of MIG weld metal (using short bursts, on a 'hot setting') to the BB threads, concentrating on the worn areas.

3) add enough blobs so that you have the equivalent area available as would be required for about four full threads

4) grind the blobs down so that the ID is the core diameter of the thread

5) retap the thread

This method is attractive because it results in a permanent repair whilst damaging very little of the paint on the frame. You might lose a couple of square inches of paint on the BB shell and that is all.

BTW I wouldn't feel that bad about stripping the thread in a Dawes frame; for years they had this quaint idea (for a supposedly quality frame) that the BB shell threads shouldn't need to be cleaned up after brazing, and that the most ill-toleranced BB cup should screw into the BB shell very easily, no matter how much distortion occurred during welding/brazing, or how much paint there is in the threads. The result of this approach is that most of the Dawes BB threads I have seen have been as slack as wizard's sleeve, or only snug by virtue of the paint in them. This can make them intrinsically unreliable; if they are slack enough I think it is a good idea to fit BB cups to supposedly 'undamaged threads' using epoxy resin in any event.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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531colin
Posts: 12507
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

Postby 531colin » 3 Jul 2016, 8:52pm

Brucey wrote:..........
BTW I wouldn't feel that bad about stripping the thread in a Dawes frame; for years they had this quaint idea (for a supposedly quality frame) that the BB shell threads shouldn't need to be cleaned up after brazing, and that the most ill-toleranced BB cup should screw into the BB shell very easily, no matter how much distortion occurred during welding/brazing, or how much paint there is in the threads. The result of this approach is that most of the Dawes BB threads I have seen have been as slack as wizard's sleeve, or only snug by virtue of the paint in them. This can make them intrinsically unreliable; if they are slack enough I think it is a good idea to fit BB cups to supposedly 'undamaged threads' using epoxy resin in any event.

cheers


For several years Dawes have simply imported boxed bikes from factories in various countries.....I rather doubt they are all manufactured in the same way as the UK made Dawes bikes.

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Redvee
Posts: 2177
Joined: 8 Mar 2010, 8:58pm

Re: Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

Postby Redvee » 4 Jul 2016, 12:55am

A frame builder should be able to ream and sleeve it for you, Argos Racing in Bristol can.

goodlife
Posts: 7
Joined: 19 Sep 2008, 3:11pm

Re: Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

Postby goodlife » 5 Jul 2016, 9:30pm

Thanks for your suggestions.
The BB is a Shimano Hollowtech, fixed cup on the drive side. After I packed and tightened the worn drive side, I noticed there was play on the non-drive side, there was room for the BB to move up and down a bit in the cup so the whole unit, including the drive side threads, rocked with pedalling. Presumably this is what caused it to come loose and start to wear the threads.

It looked like most of the wear was to the threads in the shell, so I didn't expect it to work, but I bought and fitted a new BB, and it held when i tightened it as much as I dared. So it looks like I might have got away with it this time. I shall try to learn my lesson and not ignore that kind of thing again before it's too late.

cheers,

rob.

gerrymcm
Posts: 446
Joined: 30 Oct 2012, 2:52pm

Re: Worn BB thread in Ultra Galaxy 853 frame - worth fixing?

Postby gerrymcm » 6 Jul 2016, 12:01am

I suppose as it's a HT2 BB you could still epoxy the right hand cup in (if it slackens in the future) and when the bearings go remove it via either a bearing puller or knock them out and replace them with the bearing from a new HT2.