Bottom bracket creeping to port - any suggestions?

[adonymous]

My Bob Jackson was built up fixed at the turn of the year with a Miche Primato BB and cranks. The BB cups don't have lips on them to stop lateral movement. Three times now I've noticed a slight scraping noise which on examination has turned out to be the crank spider arms coming into contact with the outside of the right chainstay. Today was the third time I've removed the cranks and adjusted the BB cups to move the cranks a wee touch (4mm or so) to the right to clear the stay. Each time they've slowly crept back and contacted the frame after about 800 miles or so. Being a bit paranoid about stripping threads on the BB shell, up till now I haven't done the cups up mega tight but today I made sure they were - to the point that there's a noticeable difference in the 'effort' needed to turn the BB spindle with the cranks off.

Should this fix the problem? I haven't used any kind of thread sealant on the BB cups up till now - is there any non-permanent product I should be using which will still allow me to remove the cups when needed? Teflon tape? Anybody got any experience with this issue and how to resolve it?

[rogerzilla]

I would take it back to whoever built it up and let them fix it, if convenient.  If not, fit a new BB as running with an over-tight one will ruin it anyway.

English BBs should actually self-tighten rather than loosen, so this is rather odd.

[aidan.f]

I had the same  problem, Threads are  probably  slightly damaged now allowing the cup to move about and loosen. Re-assemble with a smear of epoxy adhesive (araldite) as thread-lock. If  you de-grease the BB cups  + grease the shell beforehand, you will be  able to dissassemble with  a bit  of effort. I have fitted and subsequently  replaced several BB's 'bodged' in this  manner.

[Sergeant Pluck]

Have a read through this thread:

https://yacf.co.uk/forum/index.php?topic=30879.0

The Miche cups need to be tight or they will move.

In the end I gave up with the Miche as it has quite an odd chainline / chainstay clearance combination. In short, to get the right chainline it needed to be too close to the chainstay, if you have a frame that has no indentations in the chainstay such as my Bob Jackson Vigorelli. It works well with an all-Miche set-up but that's all IMO, if you are fussy about your chainline.

[adonymous]

Gents,

Cheers for your responses.  Roger and Sleepy, YHPM to this effect.

Sarge, thanks for pointing me towards that thread.  My BJ frame is a 1974 vintage and there are no indents on the outside of the stays.  Maddeningly, there are on the inside but seeing as how I'm running thin tyres and no mudguards, these are not required!

I've just had a visual check of the chainline after moving the BB starboard a bit and even without a rule it looks a couple of mm off now with the chainring slightly further out than the sprocket.

I think I'm just going to have to monitor the situation for now.  I've only done one twenty wet mile spin since moving the BB, heading out for more soon.  I usually wear my iPod on anything more than a run to the pub (yes, I know) so I think it's maybe time to turn the volume down and develop more sensitive feet.  I've got several layers of electrical tape wrapped round the relevant part of the stay now so hopwfully any movement will be detected sooner rather than later.  After reading through that thread, though, I'm thinking that a change of BB, or at least spacing out the rear sprocket, may be needed rather than just fixing the BB threads / creep issue.

Damn, more cash.

[Sergeant Pluck]

I've just had a visual check of the chainline after moving the BB starboard a bit and even without a rule it looks a couple of mm off now with the chainring slightly further out than the sprocket.

That's exactly what I had: with the correct chainline, the spider was just barely touching the paint on the stay (I'm really glad I noticed at an early stage); adjusting the cups to move the spider out a few mm obviously put the front too far out for a 42 mm chainline. Annoyingly, it did not put it out enough to work with a Goldtec hub (at least not without excessive cup bias).

Another thing I explored was just changing the BB (my thinking: even if the line is not quite right, another BB might ensure that it would at least stay put and not eat my frame) but I could never find one that ticked all the necessary boxes.

To cut a long story short, Adonymus, I wish I had realised much sooner that the Miche simply cannot work with my non-idented chainstays. This would have saved me many many pounds in failed attempts to get it all just so while retaining the Miche, farting about with a different hub and a couple of different BBs.

Campag BB and cranks give me a 42 mm chainline (or very close, AFAIR) with loads of chainstay clearance at the spider (in fact the closest clearance now is the pedal ends of the cranks).