Bottom bracket coming loose

my cup and cone BB keeps coming undone on the drive side.

the bike is an SS on a freehub with spacers. the chainline is about 2mm off, but i dont have any chain dropping problems. there is a slight tight point in the roatation but its not that noticeable.

any ideas why this might be happening? my guess is the chainline but im not totally convinced.

More likely to be the tight spot than the chainline. Every time you hit the tight spot it'll tend to work the cup and lockring. I take it you have got a lockring on it?

Loctite?

If you can rotate the chainring around a couple of holes it may get rid if the tight spot. Search on here for a couple of threads a while back about adjusting chainrings and chain tension.

i think the tightspot is mainly a result of the chainline being a bit off. unfortunatly the crank is a old cheapy with rivited chainring so it cant be adusted.

dont want to use locktitie as i wont be able to get it out again if i ever want to. i dont want to take a blowtorch to the BB shell as it would ruin the paint. at some point im going to raplce the crank and have a sealed BB.

Did you sort this?

I was riding in today and mine did the same. I changed the cranks at the weekend and thought I hadn't tightened them enough as they felt loose. I tightened them and carried on then realised the BB was unscrewing! First time that's happened in over a year of riding fixed. What the fuck?! Can't figure it out. The looks of it the RH crank is pushed upp against the BB and is acting as a lever to unscrew the BB as I ride.

Basically the BB is 'screwed' I reckon. Who are Shimano anyway?! ;)

English threaded bottom brackets are designed to unscrew when you ride, provided you cycle forwards with the bars preceding the saddle. If you cycle backwards, then I've no idea what the problem could be...

it is happening to me. i think i may have stripped the lockring/adjusting cup threads. i have taken it out and am now trying to install a simple, standard, cartridge type BB. this will no doubt cause me problems.

I am having this problem too, someone said it is from the forces of riding brakeless....
Their solution is to clean the bb cup(s?) off and put some loctite on the threads to keep it in, he said it wont come out till you want it to.
Anyone have experience with this? What loctite should I use?

This happened to me today, resulting in me having to walk home with bike on shoulder, I wonder if its a chainline issue as mine is 1mm out, should that really make a difference?

i have tried tightening the cups with a trixie tool, seems to be good, do i need to do anything else?

the drive side unscrewed a couple of mm and the right hand side crank started to be digested by the BB Cup.

:(

If the threads feel good and tight run some Loctite 242 Lock and Seal on the thread, this can be released and is BLUE, never use RED or Green

If the threads are slack you have a bigger problem, you will need to get some weld/braze run into the shell and re-tapped, this will usualy ruin the paint though. If the bike is a serious hack bike whack the shell into a slight oval and re-tap the threads, get a good bottom bracket and use some Araldite on the threads, this is the last bracket you will ever be able to fit to the frame though!

Running the chain too tight will also not help.

Hope this helps.

The Thread should be good as its virtually a brand new Orlowski frame and Campag BB. Maybe i was running the chain too tight, maybe the chainline is out and thats what affected it, the rear wheel locked up and slowed me down, the cranks would not spin ... got it home,

can chain line really bust your bike?