UN 300 vs UN XX sealed BB units

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PT1029
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UN 300 vs UN XX sealed BB units

Post by PT1029 »

Over the years I must have seen hundereds if not thousands of bikes with sealed Shimano UN XX square taper BB units. On a few occasions I have seen them with play in the bearings (usually on a very old/wellused bikes).
Hopefully the newer UN300's etc last as well, though on a low sample count (I doubt I have seen that many bikes with the new design BB unit in), I wonder.
A UN 300 about 2 months old came to me very loose in the LH bearing. It had been fitted/used on an old racer about town as a runabout (no mud guards...).
I was asked to replace it, so removed it, the photos show how it came out.
LHS bearing was very rusty, all broken up, I think some balls must have gone missing as there didn't seem that many. The outer half of the LH bearing unit didn't stay on the bearing/axle, but came out stuck in the LH cup.
The RH bearing was very stiff, I needed a spanner/grips on the axle to be able to rotate it.
As far as I can tell, the 2 black plastic rings sat each side of the LH ball race. It looked as though these were the seals to keep the rain out.
Part of the rusty metal detritus suggests that there was a bearing cage holding the balls in place, such rings are well known for breaking up and ruining bearings.
So my initial assessment would be they are far less durable than he old models
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mattheus
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Re: UN 300 vs UN XX sealed BB units

Post by mattheus »

That's good field-work PT (and a bit discouraging!).

Is there a Shimano tech-doc showing the innards of these things?

EDIT: do you have much experience of the Stronglight JP400? Similar price, a company with heritage (for what it's worth).
Jamesh
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Re: UN 300 vs UN XX sealed BB units

Post by Jamesh »

I'm guessing they outsource this low tech stuff to China hence the quality / QC isn't what it should be????

Cheers James
fastpedaller
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Re: UN 300 vs UN XX sealed BB units

Post by fastpedaller »

As these are a similar design to many eg FSA/RPM I wonder if this particular one has had particularly harsh conditions (in addition to the 'no mudguards'? maybe been through a river. I've had FSA/RPM ones on my bikes for 6 years and they are good (I always put a smear of waterproof grease on the outside seal, although I suspect this only benefits for a short period.
Prior to that I'd had the Shimano UN55 on a couple of occasions, and one only lasted a couple of thousand miles before clicking (I think that was particularly unlucky though)
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andrew_s
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Re: UN 300 vs UN XX sealed BB units

Post by andrew_s »

The UN300 are the same as most BBs, with a "sealed" bearing at each end.
The UN55 etc were a very different design, much like the old 3-piece units , with the cone on the axle, and the cups in the ends of a reasonably solid cartridge cylinder.

It doesn't surprise me at all that UN300 are compatatively short-lived, and similar to everyone else's.
zenitb
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Re: UN 300 vs UN XX sealed BB units

Post by zenitb »

Once you take the commodity produced sealed bearing approach you really are in the hands of whoever produces the bearings. I cant believe that Shimano wanted to lose control of this critical area of quality control and cant help thinking this is pure cost saving on their part.

I guess its not out of the question that we could swap the Shimano sourced sealed bearings with some better quality ones - assuming they are one of the standard sizes?

Was there any manufacturers logo on the sealed bearings that disintegrated PT ?
PH
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Re: UN 300 vs UN XX sealed BB units

Post by PH »

Jamesh wrote: 8 Jun 2021, 8:16pm I'm guessing they outsource this low tech stuff to China hence the quality / QC isn't what it should be????

Cheers James
Indonesia according to what it says on the unit.
The country of origin won't make any difference, it will be built to Shimano's spec, if that's lower than the previous BB's it's because Shimano have decided that's the way it'll be. It's hardly surprising, all their ST chainsets are low end, that's the market their ST BB's are catering for.
rogerzilla
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Re: UN 300 vs UN XX sealed BB units

Post by rogerzilla »

My suspicion is that Shimano would like to kill off square taper on decent bikes. HT2 has been around for many years, and they can't see why you wouldn't use that.
zenitb
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Re: UN 300 vs UN XX sealed BB units

Post by zenitb »

rogerzilla wrote: 9 Jun 2021, 11:00am My suspicion is that Shimano would like to kill off square taper on decent bikes. HT2 has been around for many years, and they can't see why you wouldn't use that.
yep...or Octalink...oh wait..;-)
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531colin
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Re: UN 300 vs UN XX sealed BB units

Post by 531colin »

We had all this recently.....of course I can't find it, it isn't here viewtopic.php?f=5&t=105385 which would be logical......Anybody?

Found it here...viewtopic.php?f=5&t=144549&hilit=shimano&start=15

MODS.....might be worth adding this to Brucey's stickout post linked above?

Somebody even posted a "cut-up" of a UN5X
In summary, UN 5x and the earlier FAG units (with 6 semi-circular cutouts like Campag for the tool)
....are the only ones where I'm certain the ballbearings run actually on the spindle and on the (steel) sleeve of the unit.
I've never examined a Campag, and I'm not sure of the Stronglight ones, I never cut one up.

Most so-called "unit" bearings on the market are not units at all, one bearing is part of the sleeve, usually I think its a manufactured caged bearing pressed into the sleeve, so the actual wearing parts are much smaller than in a UN5x where the bearing is part of the construction.
The other bearing is invariably a manufactured caged ballrace which fits flush up against the sleeve and is held in place by a cup; so this has the additional disadvantage of being subject to any random misalignment of the threads/facing of the shell.
All in all, much less durable than UN5x .....that unfortunately includes the Shimano 300 "replacement" which has the loose left hand bearing.
hamster
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Re: UN 300 vs UN XX sealed BB units

Post by hamster »

@531colin the newer Campag square taper units (Centaur) are dismantlable and use stock industrial bearings. The non-dismantlable earlier ones I don't know.
rogerzilla
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Re: UN 300 vs UN XX sealed BB units

Post by rogerzilla »

zenitb wrote: 10 Jun 2021, 11:19am
rogerzilla wrote: 9 Jun 2021, 11:00am My suspicion is that Shimano would like to kill off square taper on decent bikes. HT2 has been around for many years, and they can't see why you wouldn't use that.
yep...or Octalink...oh wait..;-)
The BikeRadar review of XT HT2 bearings says, without a hint of irony, "– the current versions are now regularly lasting more than six months of hard use."

I assume that's on Danny McCaskill's daily ride :D
slowster
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Re: UN 300 vs UN XX sealed BB units

Post by slowster »

531colin wrote: 10 Jun 2021, 2:07pm We had all this recently.....of course I can't find it, it isn't here viewtopic.php?f=5&t=105385 which would be logical......Anybody?

Found it here...viewtopic.php?f=5&t=144549&hilit=shimano&start=15
See also viewtopic.php?f=5&t=141038, which was the first thread covering this issue.
531colin wrote: 10 Jun 2021, 2:07pm MODS.....might be worth adding this to Brucey's stickout post linked above?
It might be better to have a separate new thread with an OP which contains links to the most useful threads about on the subject of the performance and experiences of Shimano and other brand square taper BBs, which could then be added to Too Good To Lose. There will probably be many new threads over the coming years started by people detailing their own (likely poor) experience with the new UN300/UN100 units, or suggesting better alternatives to them. I suspect most of the future threads will not provide any new insight, but occasionally there will a thread which would be worth adding to a list of links in Too Good To Lose. If you/others and the Moderators think it worth doing, I'll start a new thread and populate it with some links to get the ball rolling.
531colin wrote: 10 Jun 2021, 2:07pm Most so-called "unit" bearings on the market are not units at all, one bearing is part of the sleeve, usually I think its a manufactured caged bearing pressed into the sleeve, so the actual wearing parts are much smaller than in a UN5x where the bearing is part of the construction.
The other bearing is invariably a manufactured caged ballrace which fits flush up against the sleeve and is held in place by a cup; so this has the additional disadvantage of being subject to any random misalignment of the threads/facing of the shell.
All in all, much less durable than UN5x .....that unfortunately includes the Shimano 300 "replacement" which has the loose left hand bearing.
Most of the major UK online retailers are selling the UN300 for £20-£21 (Bikester appears to be the exception at £13.99 plus delivery). Since a Sun Race, VP or similar design BB appears to be only ~£10, is it worth paying twice as much for a UN300? If the OP's example is representative, it looks like a UN300 might be likely to last no longer than a £10 BB.

https://www.bikester.co.uk/shimano-bb-u ... 76707.html

I think a lot of German utility bikes with hub gears were formally fitted by the manufacturers with UN26/UN55 BBs, and are now being fitted with the UN300 (Shimano's Nexus and Capreo chainsets are both still square taper). I suspect that in Germany especially there might be a lot of warranty claims and complaints from irate customers and bike shops to Shimano about the U300 and UN100 if they fail so quickly.
rogerzilla
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Re: UN 300 vs UN XX sealed BB units

Post by rogerzilla »

I've found Tange Seiki BBs to be pretty good. They are the usual "two industrial cartridge bearings and a central sleeve" design, but (a) the sleeve is metal so doesn't squish like the plastic or carbon ones and (b) replacing the bearings is possible, which makes them a lot better value as a long term prospect.
fastpedaller
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Re: UN 300 vs UN XX sealed BB units

Post by fastpedaller »

rogerzilla wrote: 10 Jun 2021, 3:49pm replacing the bearings is possible, which makes them a lot better value as a long term prospect.
Only if it's possible to buy the bearings at less cost than a complete unit :)
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