BB cup moving, reason/solution?

[foxyrider]

Here's the scenario, my 'audax' bike, steel frame, full Veloce groupset, @ 6000km in last year has developed a BB issue. The RH (chainset side) bearing cup moves when i'm riding, lots of noise, occasional wobble of chainset but spinning nicely still. It's the Power Torque set up.

I have a set of replacement cups (cost sod all really so not worth mucking with old ones) however i'm loath to put them in without knowing why the originals are moving (it's only the RH that's moving, the LH is still snugged up nicely).

Any ideas? I thought initially it had unscrewed but clearly as the gap opens and closes in use its more than that. The frame is Columbus steel with a Haden BB shell.

As a comparison, my carbon bike runs SR with Ultra Torque, the cups, which are pretty much identical are rock solid. It's not a low mileage bike, it has done @ 7000km over the same period without any issue

[peetee]

Did you fit it? If so how easily did the cup go in?

[Brucey]

Any ideas? I thought initially it had unscrewed but clearly as the gap opens and closes in use its more than that. The frame is Columbus steel with a Haden BB shell.

where is 'the gap'? Presumably the frame has British threads?

IIRC the RH bearing is meant to be a sliding fit in the cup. Occasionally the fit works itself loose there and the cure is new cups.

cheers

[foxyrider]

Any ideas? I thought initially it had unscrewed but clearly as the gap opens and closes in use its more than that. The frame is Columbus steel with a Haden BB shell.

where is 'the gap'? Presumably the frame has British threads?

IIRC the RH bearing is meant to be a sliding fit in the cup. Occasionally the fit works itself loose there and the cure is new cups.

cheers

Between the cup and BB shell, yes UK built thread with British cups

[foxyrider]

Did you fit it? If so how easily did the cup go in?

Not sure to be honest, I was working in a bike shop at the time so I might have got one of the spanners to do it or I might have done it myself (shrug) - whilst I can do pretty much anything, if I can get someone to get their hands dirty I will

[Brucey]

where is 'the gap'?

Between the cup and BB shell....

one of the objections to external bearing BBs in general is that the forces of precession may not self-tighten a loose BB as well as if the bearings are inboard. In truth it doesn't always work anyway (it depends on how the parts fit and how you pedal amongst other things) but if you are seeing a lot of movement the BBcup and/or the BB shell are worn. Aluminium cups that move inside a steel BB shell can stretch the shell and ruin it, amazingly enough.

If there is a fairly rattly clearance between the BB cup and the threads then it is a really good idea to use some kind of threadlock to help retain the BB cups, else they are very likely to work loose again.

cheers

[Valbrona]

Take that cup out and you might find that the threads are jiggered.

[foxyrider]

Will have to source some suitable threadlock and then bite the bullet