My external BB thats been riden for months now spins in my scandium frame if i give it a turn. The cranks are ht2 XT so it doesnt seem be causing any issue at the moment...
But i guess this is bad and the thread must have ripped out due to my rad riding style, but could it be dangerous though? i guess not worth or possible to fix in a scandi frame?
I'd certainly have a go at using an engineering adhesive or PTFE tape on it rather than allow it to go on - that's if you can get it out
Might be the thread on the cups, or frame or both. You might get lucky and find it can be re-tapped.
If not, there are square taper BB's available which tighten up on themselves and dont use the BB shell threads.
Or the cup may have just worked loose?
Hope that helps.
thanks for info. farmers choice can you give an example of the square taper bb that might work. or will all square taper BB work?, i confess i forgot how they install as my last square taper was impossible to remove from my old 1995 marin
Have a look at the chains and BB's section of the velo solo website. Its at the bottom and called a YST threadless bottom bracket.
A normal ST BB won't help as it still requires threads in the frame. The YST jobbie doesn't.
Which could be nice.
Personally I would take it all out and have a shufty first. Re-tapping might still be viable.
the thread must have ripped out due to my rad riding style
nope, join the club.
you are the 4th one ive noticed in a short time
why the **** is the drive side a [i]none self tightening[/i] left hand thread?
you can maybe save it by going isis bb and cranks
..............i had to too
why the **** is the drive side a none self tightening left hand thread?
???
hmm it is the drive side and my riding style is not very rad 🙂
Same thing happened to me
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Looks like the bearing completely seized while being stored over the winter. First time out, the whole assembly must have turned with the cranks. Thankfully, with an aluminium BB shell and a titanium frame, there was no permanent damage!
yup mine looks like that, but the frame thread also looks similar to that but not as bad but buggered..
cant blame thread loss on thread handedness.
Shyte seized bearings in HT2 external bearing system on the other hand can walk the plank for it. At least it means your bearings seized in both the inner and outer races. If it siezes in just the outer race, then you can end up with a purty little scoreline right through your HT2 axle until......ping!
First time out, the whole assembly must have turned with the cranks.
that's some torque you must be producing druidh, thought of the olympics?
if it'sa shimano bb, the plastic insert should prevent total seizing shouldn't it ?
This is a general question to the "massive" - could the BB shell be helicoiled so that new ext BB cups could be installed.
I'm amazed that anyone can strip the thread on a BB shell/cups because the bearings are seized. Must be able to exert a lot of force. I assume that it was obvious straight away what had happened?
cynic-al - Member
that's some torque you must be producing druidh, thought of the olympics?
scaredypants - Member
if it'sa shimano bb, the plastic insert should prevent total seizing shouldn't it ?
1961Bikie - Member
I'm amazed that anyone can strip the thread on a BB shell/cups because the bearings are seized. Must be able to exert a lot of force.
I'm open to suggestions as to how else this fault can occur. Is there some other force being exerted on the bearing which I'm not aware of? I presume that the threads aren't dissolving of their own accord.
this seized bearing thing doesnt sound right in my case, the BB bearings seem to spin fine
2 spacers on drive side, shortish threaded cup - wear 'n' tear ??
If (shell) threads are knacked, I'd be tempted to threadlock it in to stop spinnage & rely on the compression from the NDS to hold it all together
I think scaredypants has a good point in that you would expect the plastic/metal interface of the insert/axle to let go before any thing too bad happens. Having said that the picture posted by druidh would suggest that it hasn't, the cup has wound out until it can go no more and then stripped.
Bugger.
Final port of call would be to get a BB that you can service the bearings easy enough without having to remove it and then araldite the thing into the frame.
I'm open to suggestions as to how else this fault can occur. Is there some other force being exerted on the bearing which I'm not aware of? I presume that the threads aren't dissolving of their own accord.
Cross threaded on assembly which partially damaged the threads on one or both components and then useage. I can't shift my Ultegra ext BB cups out of the frame even applying as much of my 102kg as I dare. So my point is that if it was seized bearings then I assume that you would feel some resistance when you stood on the pedals before the threads stripped.
Anyone have any thoughts as to my helicoil idea? Should be possible if an insert of the right size is available.
Goldtec/BETD do all sorts of cycle engineering. Mainly parts but they would probably be able to tell you if helicoil insert or other solution is available. Or a frame builder like Dave Yates/Paul Hinde/Curtis etc.
http://www.argoscycles.com/renovation-pricelist.htm
Ream and sleeve bottom bracket (thread replacement both sides) £75.00
DT78 idea isn't a bad one actually. You could contact Hope and ask if they think it would be possible to remove the bearings in their BB cups while in situ and then as suggested fix in with a high grade industrial adhesive.
[url= http://www.mountainbikecomponents.co.uk/items.asp?CategoryID=236&Name=Frame+repairs ]Bedt 's service[/URL]
Druidh your analysis is too simple. You couldn't even turn the cranks if the axle was seized. The axle would be scored etc etc.
More likely to me is that the bb cup loosened and rocked over time, destroying the threads. There could be other explanations of course.
I'm open to suggestions as to how else this fault can occur.
It's difficult to imagine anything other than the cup(s) not being installed tightly enough in the first place.
You could use a Diabolus BB these have 30% longer threads.
(shimano saint also longer on drive side)
Wholely with cynic-al here druid - there's no way you stripped it in one go like that, the threads are actually very strong and would take considerable force to shear, so much you'd notice it lock up and have to really force it against the bars. Instead I think it's more likely it's worked loose and you've chewed the threads over time. I could work out the force involved but I reckon you'd be looking at hundreds of lb/ft (i.e. jumping on a seized pedal).
out of interest - with an external bb, why is it essential to not have the bb move? the pressure on the bearings is applied through the cranks, so whilst it'll obviously f*ck the frame up, if that's already happened, what's the disadvantage of carrying on riding? Guess it might develop a little play after a bit?
We have a bike with an XTR pressfit HTII, when the bearings seize (as they do regularly with irregular use) the axle spins inside the bearing, but we've never had the bearing try to rotate in the cup. The axle is now polished where the bearing sits as its only a firm fit, unless the bearing corrodes onto the axle I can't see how you would be able to transfer enough torque to spin the bearing or cups.
scaredypants - Member
[i]2 spacers on drive side, shortish threaded cup - wear 'n' tear ??[/i]
yep, got it in one!
example, with this setup and hope bb you are left with only 10mm thread engagement (wtf)
bb cup tightening up anti-clockwise....
crank turning clockwise.....
......recipe for disaster when it gets gritty/notchy/seizes
i was fortunate though ......
..i [b]only[/b] paid £480 for my frame 😥