Several years ago I had an nice old steel frame refurbished. New Ultegra groupset fitted inc Hollowtech 2 BB and chainset. External bearings.

Flash forward a few years and miles (but not enough miles) and the left BB bearing part unwound itself out the BB on a ride in Wales at the weekend and trashed its threads in doing so. I was hopeful it didn't take out the BB shell threads as well and they seem OK (but not great). I was surprised to find the shell had not been faced (which I thought was essential for external bearing BB) so rang the frame builder/referb guy to ask why, and get his take on why the BB had wrecked itself.

"Ovalised BB" came the reply and "we don't face the BB shell as it takes off the protective paint so it rusts." Cure: £130 new BB shell and £100 repaint. Hmmm, I think. Not sure I want to do that. Apparently heavy use can ovalise the BB shell over years especially if they are not higher quality cast kind.

So I thinks- re tapping threads and fit new BB. Guy says this will not help as the BB will now be oval so the replacement bearings will still only have minimal purchase and the same will happen again.

Anyone come across this? I've read all the usual stuff about re tapping the thread and bearing retaining compount Locktight etc but cannot find any reference to Ovalisation (Ovalization) of the BB shell anywhere. Anyone? Rather not spend £230 just now thanks.

PS Helicoil anyone? or will this mean removing even more of what remains of the BB shell and leave it too weak.

May be re threaded Italian, unless it already is Italian threaded.
if so it explains right cup coming loose, its not LH threaded..

might look for a threadless BB.. some are made..

a kludge, lay in molten brass over the threads, then there is metal to re thread again.

but heating to molten brass, may loosen the brazing holding the shell on the frame tubes.

you might look for a shiny new frameset, this time torque the bearings down to spec.

Ovalizing a steel BB shell? I wouldn't think even Chris Hoy could do that.

But anyway, you can just get another set of Hollowtech II bottom bracket cups, put them in, and see what happens. You can use any of them. The Tiagra ones are pretty cheap. Worst case you're back where you started, but out the cost of a cheap set of BB cups.

I worked on a low end bike at the coop that puzzled the hell out of me
until I figured out the BB shell was ovalized. Old school loose bearing BB.

Guy was having trouble adjusting it after removing the adjustable cup
and cleaning and regreasing. I figure it had crap in the threads, so
ran the taps through it. Still the same problem, too tight to adjust
well.

When you run the taps through they force it out round again and that's
the shape as you chase or cut new threads. Not a problem, because you
have the tap handles and all that leverage. As soon as you remove
them, it springs back to oval, so you cannot adjust the bearing play
worth a damn.

But this one was a lower end bike that probably came that way from
the maker. I honestly don't see how you can ovalize a BB shell by
riding it.......wouldn't the cups kinda work against that ?

since you are using external bearing crank, I think you ought to be
OK with just putting in new bearings/cups, since you don't need to make
bearing adjustments......anyway, that's what I'd try, too.

if that does not work, you can either try a standard sealed bearing
unit in the BB, with the appropriate crank for it, or one of those
threadless things they sell at Velo Orange.

I sure wouldn't go with the frame repair except as a last resort.

it ovalized because it was ridden loose. the slight amount of play over and over stretches the metal

the OP's bike, or the one i worked on ?

op's bike. your bike i dunno. prob warped during welding. most companies thread the bb post weld so maybe i am wrong

Hi, Yes that was the first thing I did. Installed cups nicely until I tried to just nip them tight (not hard) and I could feel the threads slip. I obviously didn't force the issue and just removed them. Now with LBS to get thread on shell chased out and facing done as this is cheapest next option. If the shell has gone oval then this fix will not work.

Frame builder seemed quite convinced about ovalisation. Not from some super human effort just years of use.

Pretty sure this wasn't low end. 531 frame from high end builder originally. I'm coming round to my original thought that it was caused by the uneven facing on the BB shell and any damage to the shell threads can be fixed with a quick chasing out. I obviously hope so as this is by far the cheapest option and also means the frame still has years of service in it. The doubt is because the refurbisher/framebuilder is pretty well known and highly regarded.

Of course he was a little on the defensive but still convincing about ovalisation.

Yep that's the doomsday answer I'm hoping isn't the case. Fingers crossed.

Thanks for the replies.

Any thoughts on the Helicoil option? Will it solve oval bb shell? Will it weaken the BB shell as metal will have to be removed to fit it.?

Quesions, questions..

Italian may work but I'm thinking Helicoil will be slightly better possibility as it will introduce more not less metal

Brass option will surely mean repaint so I may as well go for the new BB shell option at a guess.

New frame is always a nice thought but I couldn't give up on my old classic without a fight.

That's unusual unless the bearing cup was threaded in very loosly. Even Italian bb's dont usually have problems with loosening the left (non-drive side) bearing cups.

That's absurd. Any older frame not specifically made for external cup bottom brackets should be faced before one is installed and "rusting" is a non-issue. All you have to do is grease the bb face and, even without grease, the seal between the bearing cup and bb face is tight enough to keep it clean.

One possible short term fix is Lock-tite on the damaged threads.

This is now my take on this as some great people here and some very experienced frame builders have all said about the same thing. Not looking good for the advice of the original expert frame builder. Cheers.