My bottom bracket is making a hell of a racket...

[LittleWheelsandBig]

What am I, your guide around the internet? Did you check out the link in the thread?

Have a look around, perhaps using those search terms, and see what you find.

 

[Blue Hills]

What am I, your guide around the internet? Did you check out the link in the thread?

Yes of course i read it - I referred to it - am a fan of that place.

I'm talking about documented failures over short to medium term - not theories.

 

[LittleWheelsandBig]

In March 2021, AndyA noted “I've seen a handful of wobbly rumbly ones already, it doesn't bode well. I reckon they'll last as poorly as their Ching Haur, RPM, Sunrace bretheren.” in that thread you referred to. Would that count as short to medium term failures?

Feel free to check out reddit and other places that refer to UN300 failures.

 

[Blue Hills]

In March 2021, AndyA noted “I've seen a handful of wobbly rumbly ones already, it doesn't bode well. I reckon they'll last as poorly as their Ching Haur, RPM, Sunrace bretheren.” in that thread you referred to. Would that count as short to medium term failures?

Feel free to check out reddit and other places that refer to UN300 failures.

please provide link from where you are quoting.

That's not that thread you and then I referred to upthread.

March 2021?

That thread was only opened on 8 June 2021.

I stress that I hold no brief for Shimano and in fact would rather the UN55 was still current. It worked. Simples.

 

[LittleWheelsandBig]

Within https://forum.cyclinguk.org/viewtopic.php?t=146281
Which I linked to

is a link to https://forum.cyclinguk.org/viewtopic.php?f=5&t=144549&hilit=shimano&start=15

which has a post by AndyA on 16 March 2021, which I quoted. I asked “Did you check out the link in the thread?”

 

[fossyant]

there used to be a UN7x and UN9x range.

Yup, still got these in both road bikes - 30 years going strong. UN71 and a UN91

 

[Ajax Bay]

Thank you LWaB

 

[rogerzilla]

Ah yes, that's the pic of the eviscerated UN55. Only two races, then, but much better-protected and with bigger balls (oo-er).

A word of warning for those considering NOS cup and cone BBs: the rubber seals don't last forever in storage, and are mostly not good after 30 years. They're better than nothing, but may squeak or be draggy until they've worn in and, even then, they'll be too hardened to effectively keep water out. I have had both symptoms on NOS 105 and DA bottom brackets. No off-the-shelf lip seals I've found will do the job.

 

[LittleWheelsandBig]

Thank you. The rest is a decent interesting answer, but on what evidence do you base the first assertion above and why do you 'think' the second. For 'extra row' (do bearings come in "rows"?) I can think of Zero engineering reasons (aka please show you're not making it up).

There are a few bottom brackets with unusual bearing arrangements that allow for the different loads on each side e.g. chain tension. A Campagnolo Chorus model uses two bearings on the RH side and one on the LH side.
https://www.bikereviewer.co.uk/campagnolo-chorus-square-taper-bottom-bracket-review/

Some just use double row cartridge bearings to try to compensate for small balls.
https://www.raceface.com/products/bb92-double-row-cinch-30mm

 

[Ajax Bay]

Thank you, LWaB. Seems like the odd edge case (bottom brackets).
I have found two UN-55s (68/ one 113 and a 115) which I expect will see me through to PBP 2023 (and maybe see you in the campsite again).

seller:​

Ruddingtonbicycles ​

Bradmorecycles 28 Far Street NG11 6PF, Nottingham, Nottinghamshire United Kingdom

 

[T4tomo]

so we've established:

• the UN300 isn't a significantly different constructions to the UN55, but arguably not quite as good
• a bloke called Andy on the internet has "seen a few wobbly ones"

In truth when something is new no-one has any idea if it will last 10+ years.

My own speculation from fitting one, because the non-drive side has no "ridge" to fit against the BB shell (in contract to the drive side) it is possible to fit it and under tighten it, which may have been the cause of Andy's wobbles.
I think its good practice to whack a bit of grease around the whole thing, help keep the worst of the weather off it.

 

[Ajax Bay]

@T4tomo, I think it's fair to say we've 'stablished that:
The UN-300 is made in the same way as most inexpensive cartridge BBs, with a central alloy section containing the bearings (one each side) held in place by two end pieces which screw into the shell. One of the endpieces is permanently bonded (glued) to the central body.
The UN-55 differs because the central section and the drive side end (threaded) is one alloy piece. But bearings both ends have to be pressed in the same way. I think, in the scheme of things, it would be fair to describe this as a "significantly different construction".
Both models have metal end-pieces*. All the bearings have been pressed into place 'the same way'. Not sure we can say whether the seal design/quality differs. I can't see why Shimano would change that, going from 55 to 300, but I don't know. So ingress of water+ is just as easy (difficult) for both models, with subsequent corrosion or not.
The UN-55 had/s a strong reputation and it's fair to say that's because of its sustained performance over millions of km. Estimate of its longevity is high, with low uncertainty, based on a mass of anecdata.
Estimates of the UN-300's longevity are subject to considerable uncertainty because there's as yet insufficient data.
As for @rogerzilla 's relating the suggestion that UN-300 failure may be due to over tightening, I really can't see any basis for that. All cartridge bearings are screwed in both sides nice and tight (49-69Nm). What would be the mechanism for over-tightening causing damage to the bearings?

*Unlike the UN-26 and its peers which have a plastic end piece on the left hand side, which over time (years) is weakened and can be a pain to get out as its splines fracture unless you're are super careful.

 

[Blue Hills]

so we've established:

• the UN300 isn't a significantly different constructions to the UN55, but arguably not quite as good
• a bloke called Andy on the internet has "seen a few wobbly ones"

In truth when something is new no-one has any idea if it will last 10+ years.

My own speculation from fitting one, because the non-drive side has no "ridge" to fit against the BB shell (in contract to the drive side) it is possible to fit it and under tighten it, which may have been the cause of Andy's wobbles.
I think its good practice to whack a bit of grease around the whole thing, help keep the worst of the weather off it.

does anyone know who this Andy is? Why he would have seen so many a year ago with issues? Is he in the trade? How many bikes does he fettle? I think it was little over a year ago that I even realised this new one had been brought in to replace the "why on earth mess with it" UN55.

 

[Blue Hills]

*Unlike the UN-26 and its peers which have a plastic end piece on the left hand side, which over time (years) is weakened and can be a pain to get out as its splines fracture unless you're are super careful.

On the UN26 - have often wondered what the difference is/was between the UN26 and UN55 - is it just the plastic cap on the non drive side? If so i have thought of just replacing it if needed with an old UN55 metal cap.
I do have a part-used UN26 taken out of a bike - a bike shop fitted it for me when I needed a new BB fitted* - I think they probably put it in (I didn't specify which one) instead of a UN55 to save a bit of money/boost their margin on the job - I don't entirely blame them.

* I had always done my own BBs and have done ever since - I let them fit the new one as I thought they had earned the work as they managed to extract my old one which I couldn't get out no matter how I tried - it had seized in thanks to the UN55 square taper's sheer reliability - it hadn't been touched since I had bought the bike. Lessons learned- always liberally grease the threads and take out/reinsert every few years.

 

[Ajax Bay]

UN-26 (looks as if both end-pieces are separate to central body, @Blue Hills ):

UN-55 (holding by left end of spindle):