bottom bracket issue - cups keep working loose

redvision

Hi all,

Wondering if someone can offer me some advice,

My training bike has a square taper BB but ever since i bought it (3 years ago) i have had nothing but problems with the non-drive side cup working loose.
Several LBS have looked at it and each time try to use loctite to hold in place, but a thousand or so miles later and exactly the same thing happens.
They also warned me that each time it works loose the threads slowly get worn away which will exacerbate the problem long term - yet each shop who has looked at it have not found any issues with the threads.

I noticed yesterday that the chainset had play in it yet again, looked at the BB and indeed, the non-drive side cup has worked its way out by about 2mm again.

There seems very little point in taking it to the shop for them to tighten it back up - i have the tool to do it myself. I just wanted to ask for opinions on why this keeps happening and what, if anything, can be done to to and cure it once and for all because it is driving me mad!

Thanks for any advice

dj58

What make/model BB is it? Have the BB threads been chased through, has the frame been faced?

craker

Have you tried changing it? Some brands have metal non-drive side cups, most Shimano ones I've seen are plastic.

Facing seems plausible, I can't think why a properly done up BB would work loose otherwise (originally cut with a worn tools and has cut too much material away perhaps).

FWIW the thread went on my old Raleigh and I've swapped out the BB for one of those self threading ones where the drive side screws directly into the non-drive side. You might have to put a chamfer on the inside of your bb shell, as the up down movement of the axle can cause the cup to loosen off. That might be something to have a go with with your current BB of course.

redvision

Hiya DJ, its a square taper BB (Shimano UN 55 if i remember correctly).

Nope, the frame has not been faced since i bought the bike. None of the shops have even suggested this. Would it be needed for this type of BB?

Thanks

redvision

craker wrote:

Have you tried changing it? Some brands have metal non-drive side cups, most Shimano ones I've seen are plastic.

Facing seems plausible, I can't think why a properly done up BB would work loose otherwise (originally cut with a worn tools and has cut too much material away perhaps).

FWIW the thread went on my old Raleigh and I've swapped out the BB for one of those self threading ones where the drive side screws directly into the non-drive side. You might have to put a chamfer on the inside of your bb shell, as the up down movement of the axle can cause the cup to loosen off. That might be something to have a go with with your current BB of course.

This is really interesting. The last time it was changed was in October and the actual BB still feels silky smooth.
Im surprised the shops have not mentioned facing at all. I always assumed that was only necessary for the external ones and so i didnt even think to ask them about it. Could it really be the primary cause?
Any idea how much it costs to do?

The very fact that none of those who have looked at it have even suggest this as a possibility makes me wonder if i should try and find another lbs - although there aren't any others close by (within 40miles)

Manc33

I took mine to a shop expecting them to put the BB tool in a vice and rest the whole bike on that to tighten it (the reason I couldn't do it tight enough at home).

What happened was... the mechanic didn't move the bike anywhere, he just squatted down with a special Park Tool thing (it looked like a giant wing nut) and turned it by hand.

I just hope it never comes loose. :roll:

If yours keeps coming loose... did you see how the LBS tightened it? By hand on the floor, or on a vice?

Maybe its just not being tightened enough, I don't understand how it can be by hand (without using the frame for leverage).

Like I said ages ago on here the splines on those BB cups make it so you cannot tighten it, I would think apart from using a vice it cannot realistically be done.

A lot of people say just tighten it up enough by hand and ride the bike, it will tighten itself - sure it will. :roll: Maybe in theory thats what it is meant to do, I won't argue about that part. Thing is I am talking about the real world.

redvision

Manc33 wrote:

If yours keeps coming loose... did you see how the LBS tightened it? By hand on the floor, or on a vice?

Maybe its just not being tightened enough, I don't understand how it can be by hand (without using the frame for leverage).

Like I said ages ago on here the splines on those BB cups make it so you cannot tighten it, I would think apart from using a vice it cannot realistically be done.

A lot of people say just tighten it up enough by hand and ride the bike, it will tighten itself - sure it will. :roll: Maybe in theory thats what it is meant to do, I won't argue about that part. Thing is I am talking about the real world.

Yes i did. The last shop which had it (when they put in the new BB) fitted it in front of me. They used something similar to this http://www.merlincycles.com/shimano-tl- ... 44486.html (which is what i have since bought) and they tightened it with a wrench.
They seemed to use as much force as they could and it did seem seated perfectly. IIRC they actually said thats going to be a ******* to get off when this BB goes.

Since then though it has somehow once again slowly worked its way loose

dj58

redvision wrote:

Hiya DJ, its a square taper BB (Shimano UN 55 if i remember correctly).

Nope, the frame has not been faced since i bought the bike. None of the shops have even suggested this. Would it be needed for this type of BB?

Thanks

Facing may be required If using a square taper BB with a separate lock ring or HT II type external bearing cups, depends on how good the tolerances on the frame are. However the UN 55 doesn't use an external lock ring, although it does have a shoulder that butts up to the BB shell.

Inspect the BB shell threads carefully. How many BB's have you had fitted to date and has the problem occurred with each BB?

http://www.parktool.com/blog/repair-hel ... ng-bts-bfs

redvision

DJ58 wrote:

Facing may be required If using a square taper BB with a separate lock ring or HT II type external bearing cups, depends on how good the tolerances on the frame are. However the UN 55 doesn't use and external lock ring, although it does have a shoulder that butts up to the BB shell.

Inspect the BB shell threads carefully. How many BB's have you had fitted to date and has the problem occurred with each BB?

http://www.parktool.com/blog/repair-hel ... ng-bts-bfs

Well i think it has been tightened about 6 times in the 3 years, and in that time has also had 2 brand new BBs.

Thanks for the link. I am starting to think that maybe it does need to be faced. Worth a shot at least. In which case it will be back to the lbs

dj58

Take the non-drive side cup out and inspect the threads, and those inside the BB shell to see if there are any witness marks that would indicate that the BB threads on the non-drive side are damaged. It could be that the BB threads have not been machined parallel or are out of tolerance or damaged in some way.

"Most bottom bracket shells have an internal thread to accept bottom bracket bearing units from numerous manufacturers. If these threads are not in acceptable condition, they may need preparation. Threads may need realignment, or may have weld splatter from manufacturing that prevents the threading of the bearings. Shells may be out of round due to welding during manufacturing. Additionally, some bearing system benefit from having the faces of the shell square to improve bearing adjustment and bearing longevity. If the shell faces are deformed, and are not parallel to one another, the left and right bearing may not be concentric to one another. Machining the shell face improves concentricity."

desweller

That doesn't sounds good at all. If the thread flank is not correctly formed you can get a scenario where there's not enough friction to stop the screw undoing.

I would have one more shot at loctite-ing the BB in (after thoroughly cleaning the threads with isopropyl alcohol), if it come loose again it might be worth switching to a threadless design.

Matthewfalle

If normal blue Loctite doesn't work you can always work your way up the range (Blue, green, red) but bear in mind once it's in there with red it's going to take a lot of effort to get it out come replacement time ..........

redvision

Morning,

So, an update,

On the way home last night I decided to call in at the LBS which put the new BB in last October. They told me to go and get the bike and they would take a look.

Two mechanics looked at it, they took off the NDS cup (to give you an example of how loose it was they did this by hand!) cleaned it all out and then thoroughly checked the threads. They couldn't find any problem at all. I asked about it being faced and they said they didn't think it would need it but (because i was standing by them i think) they took out the whole BB and used some tool i had never seen before to check. All they found was a very slight overlap of paint on the NDS. When they found this i thought YES, problem solved, but they insisted this wasn't enough to cause the issues. :evil:

They put everything back together for me, putting in yet another brand new BB (the other was silky smooth but they said you might as well change it now) and used loctite red 243. I made sure they tightened it up as tight as possible.

To be fair to them they said they have never experienced this issue before and they are going to contact a few other shops today to see if anyone has any experience of this. They have also offered to contact the frame manufacturer as well, although i don't think that will get anywhere as the bike is just outside of the warranty period.

They only charged me £15 for everything which i thought was fully respectable and they also said that they will cover the lot for 6 months, so if it does work loose again i will be straight back down there.

This said, i think its probably a good idea to start looking for an alternative frame as i fully expect the cup to be loose again in about 1000miles

Thanks for your all your help and advice, really appreciate it.

bill57

In all my cycling years I've never come across a bottom bracket cup that could be screwed/unscrewed more than a third of the way by hand. Do you actually mean without a lever of any kind?
If this is indeed the case, I can't see why facing it would make any difference. It's simply too loose, and by the sounds of it, the thread has been overcut.
What kind of frame is it, steel, alloy or carbon fibre?

keezx

Amazing indeed. never a cup came loose in 40 years with me.
Must be worn-out threads.

dj58

redivision, As a matter of interest what make of frame is your bike and did you buy it new or second hand, complete bike or frame/forks for a self build?

redvision

Evening all,

So just a quick update, the BB worked loose again at start of April. LBS decided it was worth contacting the manufacturer (Felt) as they could not solve it.
Just before leaving work today i had a phonecall from the LBS, Felt could not find a fault with the BB/threads but actually found an issue with the alignment of the rear dropouts, and even though its out of warranty (just) they have offered a replacement frame!

So very grateful to them for that.
Although hope its more reliable than the first!

Would an alignment issue with the rear drop outs really cause the issue with the BB working loose though?? :?

keef66

I cannot see how rear wheel alignment could possibly affect the BB. But good result I'd say.

My son has a Felt with a square taper BB so I'll be keeping an eye on it though.

redvision

keef66 wrote:

I cannot see how rear wheel alignment could possibly affect the BB

This was exactly my thought and the LBS were also not convinced.
But at least the frame is being replaced, so definitely a good result.


Thanks for all the help and advice fellas, much appreciated.