UN55 BBs not so good anymore?

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fastpedaller
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Re: UN55 BBs not so good anymore?

Post by fastpedaller »

Against my 'gut feeling,' I decided to see if an FSA/RPM unit would come apart - that's the last time I try that! I should have waited until I could get a wrecked one from a skip.
IMHO (and now experience, albeit of 1 try) It is impossible to do with any knowledge of whether the outcome will be good or bad.
I used an old BB shell and screwed the LH cup in - a light whack with an alloy hammer onto the axle and the Lh cup was off. No drama there, and I was confident no damage was done. Next - how to get the bearings off the axle? There is NOTHING to grip except either one of the bearings or the spacer tube. Because each bearing abuts a shoulder on the axle, there is no possibility of pressing on the INSIDE race of the bearing in order to get it off. Some Youtube clips show folk holding the spacer tube and whacking the axle with an alloy hammer, and yes that will work, but only if the interference fit is light. I tried holding the spacer by hand, and also in the vice (as it was doomed at that stage anyway). the result was one smashed bearing, and another I'd be reluctant to rely on. An unmitigated disaster and I also had to grind 2 flats on the inner race of the broken bearing to split it and remove it from the axle. Having now got it apart, I may purchase some bearings and rebuild it..... It's not really economical, but on the basis that I can remove the inner seals and load the bearings with plenty of grease, the outcome will be what I was aiming for. In hindsight, grinding and punching a small hole in the spacer and squirting SFG in seems a much better idea than attempting to remove the bearings on a good unit.
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bgnukem
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Joined: 20 Dec 2010, 5:21pm

Re: UN55 BBs not so good anymore?

Post by bgnukem »

I guess when the sleeve is fitted there's no space to get the arms of a puller behind the outer bearing ring and remove it that way? Even so, the removal force would be passing through the bearing and would likely damage it.

Grinding a hole in the shell and filling it with grease is one thing, but if the bearing inner shields remain in situ then not much grease is going to enter the bearings themselves.
fastpedaller
Posts: 3435
Joined: 10 Jul 2014, 1:12pm
Location: Norfolk

Re: UN55 BBs not so good anymore?

Post by fastpedaller »

bgnukem wrote:I guess when the sleeve is fitted there's no space to get the arms of a puller behind the outer bearing ring and remove it that way? Even so, the removal force would be passing through the bearing and would likely damage it.

Grinding a hole in the shell and filling it with grease is one thing, but if the bearing inner shields remain in situ then not much grease is going to enter the bearings themselves.


there is no means of getting a bearing puller between the pacer and a bearing - until the bearing is moved.... catch 22
I guess if it's Semi-Fluid Grease, then it's thin enough to flow into place and get through the inner seals. What other options are there? the 'foam on the outside' idea is a good one.... foam or felt soaked in grease and then held in position with an O-ring on the axle may stop any ingress?
robc02
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Re: UN55 BBs not so good anymore?

Post by robc02 »

Just to clarify: When I said "tapping", I meant just that - a light tap or two. The whole thing came apart very easily with very little chance of damaging the bearing.

I have worked on two Token units now and both were easy to take apart - so easy I forget the exact details!
fastpedaller
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Joined: 10 Jul 2014, 1:12pm
Location: Norfolk

Re: UN55 BBs not so good anymore?

Post by fastpedaller »

robc02 wrote:Just to clarify: When I said "tapping", I meant just that - a light tap or two. The whole thing came apart very easily with very little chance of damaging the bearing.

I have worked on two Token units now and both were easy to take apart - so easy I forget the exact details!

The FSA/RPM ones are a very tight fit on the axle! As evidenced above. Ok to rebuild of course, as It's possible to press them on with the correct size of tube.
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Sweep
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Joined: 20 Oct 2011, 4:57pm
Location: London

Re: UN55 BBs not so good anymore?

Post by Sweep »

Rather than advanced deconstruction, anyone got any feedback on the Shimano replacements yet?
Sweep
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: UN55 BBs not so good anymore?

Post by Brucey »

fastpedaller wrote:...I used an old BB shell and screwed the LH cup in - a light whack with an alloy hammer onto the axle and the Lh cup was off. No drama there, and I was confident no damage was done. Next - how to get the bearings off the axle? There is NOTHING to grip except either one of the bearings or the spacer tube....


Am I to take it that you mean the RH (DS) cup was off, as well as the LH cup? So that you had just the two bearings and the spacer tube on the spindle?

If so (as I mentioned previously) at this point you can simply displace the spacer tube sideways (there is nothing holding it apart from friction) and add as much SFG as you like. Or drill a hole in the sleeve and catch/remove the swarf. You can also (destructively ) remove the inner seals. To remove the seals, pry the exposed part of the seal of the bearing, and cut it radially using side cutters (which generates no swarf). Then either tug the seal out whilst moving the spacer tube appropriately, or tuck the seal back in, slide the tube the other way, and repeat the cutting. Now you have each seal in two halves, which can be pulled out. The seals are normally thin brass, overmoulded with rubber, and are not very difficult to cut. If you can't cut the seal, simply gripping it with snipe nosed pliers and wiggling it will soon fatigue and break the brass part.

If you have got both cups off and want to get a bearing off the spindle this is also possible. Again slide the spacer to one side, and support one bearing over the edge of bench vice jaws. Some tapping with a soft hammer is usually enough to shift the bearing. [Yes, the load is reacted through the centre part of the bearing but this shouldn't be so large a load that you damage the bearing.] If the spacer tube is a cheap steel part (as is normally the case, but not in the Token units) then if you don't like the way the bearing is supported, you can simply crush the spacer tube slightly in order to give the bearing better support; this allows a 'straighter push' and the bearing will come off more easily. A cheap steel spacer tube can be made round again subsequently by working it using a hammer and a suitably sized socket.

I have dismantled literally dozens of these things (mostly used ones, where rust causes the bearings to bind and not want to come off the spindle so easily) and I don't remember breaking one in the process. Maybe yours was unusually tight for some reason?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Brucey
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Re: UN55 BBs not so good anymore?

Post by Brucey »

Brucey wrote: …. I don't remember breaking one in the process. Maybe yours was unusually tight for some reason?....


I shall remember now.... I decided to start the day with a bang and dismantle a lightly used 'powerpro' BB of this pattern.

the victim
the victim


poised for RH cup removal
poised for RH cup removal


seconds later
seconds later


now for the trickier bit
now for the trickier bit


oops….
oops….


so it all went to plan apart from the last bit. The reason why the outer part of the RH bearing isn't in the final photo is because it lies, in pieces, in at least two distant corners of the workshop. So some of these BB units do have tighter bearings than others for sure; the bearing hadn't moved at what I considered to be a 'normal' level of force so I hit it harder (much harder than I thought was either safe or would do normally) and lo and behold it broke. I wasn't that surprised, given how hard I hit it.

So if I wanted an easy life I should have quit whilst I was ahead, after the third photo. I also had a quick go at removing a seal with the spacer tube in situ and it was less easy than I remembered; perhaps the shoulders on the axle are slightly larger than other BB units of this pattern, giving you less space to work in. IIRC it should instead be possible to remove the outer seals and then poke the inner seals out of position, through the bearing. They can stay inside the spacer tube, floating around on the spindle, drowned in grease; they are unlikely to do much harm there.

FWIW I have seen several of these 'powerpro' units where the bearing outer has cracked in service, so it seems quite likely that the bearing steel they use is not at all tough. The bearing was marked 'TH Industries' (which means Thun Industries I think, who presumably make 'powerpro' BB units) and 'KKK' which I assume to be the cartridge bearing manufacturer.

New balls please!

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
rjb
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Re: UN55 BBs not so good anymore?

Post by rjb »

And here's another, a Kinex made in Slovakia. Was surprised by how few balls there were inside, 7 each side from memory. To assemble it you can only insert 1/2 an arc as then there is no room to squeeze another one in. You spread them out evenly then insert the nylon ball separator/retainer.
The fag ones I've dismantled were very similar in construction.

IMG_20201117_114655.jpg


The new Shimano un300 use the same size bearings as the old stronglight 650? Unit, but the stronglight one spreads the bearings further apart which reduces the bearing load.

Stronglight
Stronglight
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
fastpedaller
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Location: Norfolk

Re: UN55 BBs not so good anymore?

Post by fastpedaller »

Your story wiih the Powerpro was exactly my experience. The inner sleeve on mine wouldn't budge, also the broken bearing was the result of my reluctance to give up. Mine was an FSA/RPM Powerpro, bearings were marked FSA. Bearing races very hard, therefore prone to cracking?
Putting some thought into this, I've now realised there's a relatively easy way to get a serviceable BB......... just use a 73mm one of your chosen length, remove the inner sleeve by destruction, and the bearing inner seals can be removed so lots of waterproof grease can be added. When fitted to a 68mm shell, this gives a handy 5mm for a traditional lockring to be used to adjust the LH cup so there is a smidgeon of pre-load!
FP
Brucey
Posts: 44513
Joined: 4 Jan 2012, 6:25pm

Re: UN55 BBs not so good anymore?

Post by Brucey »

fastpedaller wrote: ...Putting some thought into this, I've now realised there's a relatively easy way to get a serviceable BB......... just use a 73mm one of your chosen length, remove the inner sleeve by destruction, and the bearing inner seals can be removed so lots of waterproof grease can be added. When fitted to a 68mm shell, this gives a handy 5mm for a traditional lockring to be used to adjust the LH cup so there is a smidgeon of pre-load!


yes that could work but I suspect you would need to use retaining compound on bearings where they fit into the cups; the fit is a bit slack and the bearings are normally at least partially retained by the load passing through the sleeve, which would no longer be present of course. This route has another appeal which is that there should be scope for fine-tuning the chainline, using a spacer on the RH cup.

Come to think of it, it may be possible to add a spacer between the LH cup and the LH bearing in a 68mm unit and make enough space for a lockring that way, too.

BTW you can indeed dislodge the inner seals by poking through the bearing, having removed the outer seals. This means that plenty of grease can be added, filling up the centre void if required

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
bgnukem
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Joined: 20 Dec 2010, 5:21pm

Re: UN55 BBs not so good anymore?

Post by bgnukem »

I've often thought it would be nice to be able to control the insertion of the LH cup with a lockring, given that tightening the cup to varying degrees seems to pre-load the bearings and can make them quite rough and 'notchy'.

Might have a go at dismantling my Token BB and removing the bearing inner seals, if the RH cup can be separated from it's bearing without destroying the bearing. I have a feeling water ingress would kill off the bracket pretty soon anyway. Cost around 35 quid too!

What would be a suitable semifluid grease to fill the BB shell, and would the grease harm the carbon fibre sleeve?
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: UN55 BBs not so good anymore?

Post by Brucey »

bgnukem wrote:Might have a go at dismantling my Token BB and removing the bearing inner seals, if the RH cup can be separated from it's bearing without destroying the bearing. I have a feeling water ingress would kill off the bracket pretty soon anyway.


yes they do die after as little as one winter unless you do something with them. You can get both 'token' cups off easily enough, and IIRC the bearings come off the spindle too, but as noted above you don't need to do this to get grease into the centre sleeve; you can prod the inner seals through the bearing, having removed the outer seals.

Re SFG; anything is better than nothing, and something with solid lubricants and corrosion inhibitors is better than that.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
fastpedaller
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Location: Norfolk

Re: UN55 BBs not so good anymore?

Post by fastpedaller »

Brucey wrote:
yes that could work but I suspect you would need to use retaining compound on bearings where they fit into the cups; the fit is a bit slack and the bearings are normally at least partially retained by the load passing through the sleeve, which would no longer be present of course. This route has another appeal which is that there should be scope for fine-tuning the chainline, using a spacer on the RH cup.

Come to think of it, it may be possible to add a spacer between the LH cup and the LH bearing in a 68mm unit and make enough space for a lockring that way, too.

BTW you can indeed dislodge the inner seals by poking through the bearing, having removed the outer seals. This means that plenty of grease can be added, filling up the centre void if required

cheers


I'd be reluctant to try and dislodge the outer seals because (from the FSA experience yesterday) they fit into a groove in the outer race, so could be easily damaged. I note your comment about retaining compound, which leads me to ask.... Do the expensive separate bb units without a structural sleeve use retaining compound? can we just rely on a small preload to hold the outer races?
There's another possible bonus to this idea, in that an additional shield (eg made using old inner tube) could be sandwiched between each cup and its bearing, this could also act as a 'spring washer' thus preventing the bearings rotating in the cups?
fastpedaller
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Location: Norfolk

Re: UN55 BBs not so good anymore?

Post by fastpedaller »

This looks to be the same type of construction as the UN55 - can't say I'm a fan of the blue cups, but I could accept them if the unit works

https://www.ebay.co.uk/itm/68x103-124-5 ... %7Ciid%3A1
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