- Location
- London
not being funny but I never realised that pressfit couldn't be sorted at home - they are a mystery to me. And the word "press" makes everything sound so simple.
My bottom bracket is making a hell of a racket...
- Thread starter T4tomo
- Start date
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Ajax Bay
Guru
- Location
- East Devon
@rogerzilla Roger - please can you share any reasons for your deprecation of the UN-300? I held the UN-55 as a BB I'd spend a premium on because of its reputation and a couple waiting to be pressed (screwed) into use (various bikes, some 68, some 73 shell). I want them to run as smoothly and for as long as 'Special Green' (it's a wax) on a frosty ski.
Typed this and then went looking for answers - so same Q as @Blue Hills While looking here are some sites (which don't add value. I particularly thought the 'restoration' site was useless: UN-300 costs less and is lined up with Tourney, so it must be worse. No: the few remaining UN-55s cost more because they are increasingly scarce (I wish I bought a 100: seriously better than the NYSE. I could find no comparative reviews.
Both 55 and 300 are the same outward spec. The key difference (not the washer thing: what's its function, in practice?) seems to be that whereas the 55's threaded interface on the drive end is integral with the BB body, the 300 threaded section is bonded to the body (so effectively slides on like the non-drive side end does, to hold the BB securely in position. Assume cheaper to manufacture; but has that an adverse effect on performance (smoothness and logevity)?
https://www.mantel.com/uk/shimano-bb-un300 - cheapest I could find for the UN-300 (but NB £10 shipping from UK).
Here's one for the OP: https://www.acebikeco.com/components/gears-drivetrain/shimano-un55-bottom-bracket__8819?
Typed this and then went looking for answers - so same Q as @Blue Hills While looking here are some sites (which don't add value. I particularly thought the 'restoration' site was useless: UN-300 costs less and is lined up with Tourney, so it must be worse. No: the few remaining UN-55s cost more because they are increasingly scarce (I wish I bought a 100: seriously better than the NYSE. I could find no comparative reviews.
Both 55 and 300 are the same outward spec. The key difference (not the washer thing: what's its function, in practice?) seems to be that whereas the 55's threaded interface on the drive end is integral with the BB body, the 300 threaded section is bonded to the body (so effectively slides on like the non-drive side end does, to hold the BB securely in position. Assume cheaper to manufacture; but has that an adverse effect on performance (smoothness and logevity)?
https://www.mantel.com/uk/shimano-bb-un300 - cheapest I could find for the UN-300 (but NB £10 shipping from UK).
Here's one for the OP: https://www.acebikeco.com/components/gears-drivetrain/shimano-un55-bottom-bracket__8819?
rogerzilla
Legendary Member
The UN300 BB already isn't holding up well in the real world. The UN55 is heavy but usually goes on for years and years. Mind you, even the UN55 is a low- to mid-range component; there used to be a UN7x and UN9x range.
In summary: the UN300 is like most cartridge BBs, in that it uses a pair of 6903 bearings trapped between the cups and a central sleeve (which needs to be very stiff, or the bearings experience shear, and bind when the cups are tightened). Your frame had also better have good parallel threads and a well-faced RH to the shell. Water sealing is fairly rudimentary. It's a Tourney-level component. The UN55 was a unit design (sleeve integral) so not sensitive to cup tightness, relatively insensitive to poor BB shell prep, and I think it had an extra row of bearings. It was very well sealed.
In summary: the UN300 is like most cartridge BBs, in that it uses a pair of 6903 bearings trapped between the cups and a central sleeve (which needs to be very stiff, or the bearings experience shear, and bind when the cups are tightened). Your frame had also better have good parallel threads and a well-faced RH to the shell. Water sealing is fairly rudimentary. It's a Tourney-level component. The UN55 was a unit design (sleeve integral) so not sensitive to cup tightness, relatively insensitive to poor BB shell prep, and I think it had an extra row of bearings. It was very well sealed.
Ajax Bay
Guru
- Location
- East Devon
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).
I never had a problem, you just need a different tool.
rogerzilla
Legendary Member
There are lots of stories of early UN300 failure if you search. Overtightening the cups may be a factor because of the design.
I'm fairly sure I saw a cut-up UN55 and it had more than two races, but I can't find the photo. If I still have the old 107mm UN55 I commuted on for years, I'll saw it up. As for engineering reasons: Dura-Ace pedals have three races, Hugi hubs (and clones like DT) have four races...
I'm fairly sure I saw a cut-up UN55 and it had more than two races, but I can't find the photo. If I still have the old 107mm UN55 I commuted on for years, I'll saw it up. As for engineering reasons: Dura-Ace pedals have three races, Hugi hubs (and clones like DT) have four races...
Ajax Bay
Guru
- Location
- East Devon
I have searched for "UN-300 failure" Roger (this morning, this afternon and just now). Clearly you have google fu. Would have thought you could find maybe just one link. Anyone else want to contribute? Pedals are cantilevers as, effectively, are rear/freehubs. Engineering requirement is different.
Of course these hubs "have four races": two bearings, each with an inner and an outer race.
DT-Swiss front hub:
DT Hugi Hubs - The ultimate cycle touring hubs? NO!
The matching front hub is more conventional with two of the 6000 series bearings and a tough 16 mm alloy axle.
presta
Guru
I'm not surprised it broke up if you were pedalling at 7420 RPM.
- Location
- London
Must admit I was wondering if it has been around long enough for real world data on it.
(I won't be able to contribute for a fair old while due to my stocks of UN55s)
OP
OP
T4tomo
Legendary Member
Mine has done 1 ride and been absolutely fine, I'd say that's 100% reliability for the UN300.
fossyant
Ride It Like You Stole It!
- Location
- South Manchester
I've 6 months on my UN300 and it's mainly been ridden in crap conditions - water and mud. So far so good.
OldShep
Über Member
- Location
- South West Scotland
Add Shimano and take out the dash is more fruitful.I have searched for "UN-300 failure" Roger (this morning, this afternon and just now). Clearly you have google fu. Would have thought you could find maybe just one link. Anyone else want to contribute? Pedals are cantilevers as, effectively, are rear/freehubs. Engineering requirement is different.
Of course these hubs "have four races": two bearings, each with an inner and an outer race.
DT-Swiss front hub:
View attachment 630923
DT Hugi Hubs - The ultimate cycle touring hubs? NO!
https://www.bretonbikes.com › homepage › cycling-article-blog › 103-dt-hugi-hubs-the-ultimate-cycle-touring-hubs-no
The matching front hub is more conventional with two of the 6000 series bearings and a tough 16 mm alloy axle.
Ajax Bay
Guru
- Location
- East Devon
Nope. Zero. Maybe https://duckduckgo.com/?q=shimano+un300+failure&t=ffab&ia=web
just doesn't want me to see @rogerzilla 's "lots of stories of early UN300 failure".
It's entirely possible that "it has[n't] been around long enough for real world data on it." credit @Blue Hills
I see noone else (other than Roger) is asserting its lack of longevity.
I'm just looking for information to inform my next choice: a UN-300 or Stronglight JP400.
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LittleWheelsandBig
Veteran
‘Shimano UN300 failure’ found several reports for me, mostly on other forums.
https://forum.cyclinguk.org/viewtopic.php?t=146281
https://forum.cyclinguk.org/viewtopic.php?t=146281
- Location
- London
isn't that one failure?
and someone suggested that it might have been a quality control issue?
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