What will replace the quality of the discontinued Shimano BB-UN55?

[silva]

Sorry, but I hammer my bikes. Used to get 12-18 months out of a UN55. So far this UN300 is holding up well. You aren't Chris Hoy you know. Any BB will be way stronger than you are. What fails is the bearings due to ingress of dirt and water.

Octalink was a crap design and we kept telling you to get rid. Square taper is fine, and these cartridge units are very robust and long lasting.

Well I didn't gave up to save the bucks!
And in the end I found the cause of the losening: water.
Once dried out, I wrapped inner tube around the bottom bracket and the crank didn't loose anymore;
And rode further 17 months without a problem.
And likely, if the frame hadn't broke, many more.
That Octalink bb was priced 60 euro's. That's 70 days a bag of 200 gr potato chips paprika.

But the frame broke, it had to be dismounted, and remounting it, maybe splines got damaged and a suddenly losing crank is quite a safety risk, so time to getting rid of it.

I now have a spare brandnew Shimano BB-5500 70mm M36 118.5 mm length for sale. It was 60 euro, for 30 you get it, and bonus a loosening left crank. Fun guaranteed! PM if interested. Be insured.

 

[silva]

Sorry, but I hammer my bikes. Used to get 12-18 months out of a UN55. So far this UN300 is holding up well. You aren't Chris Hoy you know. Any BB will be way stronger than you are. What fails is the bearings due to ingress of dirt and water.

Octalink was a crap design and we kept telling you to get rid. Square taper is fine, and these cartridge units are very robust and long lasting.

Do you also hammer in the backwards direction?
Aka, are your bikes fixed gear?
Those are hammering from both directions.
Helps in demolition works.

I thought I wasn't a skidding phun kid, but my rear tyres shows an all around series skid patches, alike I am.
From just riding straight while resisting the backwards pedal.
Maybe that's the reason why on the avatar bike the rear tyres last 1 year and on the prevous bike 2 years.

But the latter was before the dumping of the freewheel / move to fixed.

I thought at 1st it was due to wider Schwalbe SuperMotoX instead of MarathonPlus but it's due to ehm "straight skidding".
I notice on my previous spare, now in use due to broken frame avatar bike, bike now also faster than before 2017 rear tyre wear.
The avatar bikes frame broke in may. The Marathon Plus profile looked then like new. I had replaced it and little further usage up to may. It's now 10 weeks further and 2 mm less, making the wide SuperMotoX looking instead better.
Also the wear out of center, a mystery, but possibly due to me having some "natural" habit;tendency to steadily slow down by resisting one pedal more times than the other, what I 'fixed' by flipping the tyre to chew some more months out of it.

So ppl that move to fixed gear and no brakes, win bucks on metal, lose bucks on rubber.

 

[fossyant]

I used to commute on fixed.

 

[Fastpedaller]

Crikey - this is getting long-winded. Anyone seriously worried about the longevity of their cartridge bottom brackets can 'fix' them so the likelihood of bearing failure is minimal. I don't lay claim to be the 'inventor' of this idea - there is more on the Cycling UK Forum where Brucey goes into great detail. The main issue is the bearings are primarily used for fast rotation/ low load parts (ie not clycles), and therefore they need extra lubrication for cycle use. A little grinding (and the use of a centre pop) can make two holes (one 'either end' ) to enable semi-fluid grease to be added (aerosol can/tube aimed at both bearings) which will provide extra lubrication before the unit is fitted. Brucey also advocates the alternative method of carefully prising off the outer seals and adding grease - I've not the courage to try that myself. Another ploy is to avoid grit/water entering from outside, so a greasy felt washer between the BB and crank may do a good job?

 

[rogerzilla]

Misalignment also ruins this design of BB. In the days of cup and cone BBs, any half decent bike shop would chase and face the BB shell of a new frame. The UN-55 type BB made that less critical since both bearings are in one rigid assembly and the LH "cup" is a fairly sloppy fit. Now it's critical again but shops have got out of the habit.

 

[Ajax Bay]

I suggest that, as you highlight, since the spindle and bearings are in one rigid assembly, any misalignment of the BB shell (angle and co-centring) minimally affects a cartridge BB like the UN-300 or UN-55. The LH 'cup' fixes this rigid assembly in a fixed position.
Not quite sure what development (square taper cartridge BB) you think has made it "critical again"?
'Chasing and facing' was fine with metal BB shells: comes with risks for carbon.

 

[rogerzilla]

The UN-300 uses the common design of two bearings separated by a central sleeve. It's not a unit design.

 

[Fastpedaller]

In an idle moment I decided to take a hammer to a new (in my new spares drawer) NECO bottom bracket cartridge (very similar to UN300). After removing the LHS cup I opened the vice jaws and rested the inside of the RH cup on them - a very small tap with an aluminium alloy hammer and the axle fell out, leaving the sleeve and Rh bearing attached to the cup, and the LH bearing still on the axle of course.. No drama and nothing broken, I attacked the inner seal of the LH bearing with a metal scribe and managed to yank it off. The bearing had some grease in it, but I packed it full of grease. The RH bearing seal was a little more difficult to remove because the access was through the length of the sleeve, but the same packing was carried out. If I get around to using this BB I think it will last longer because of its extra initial lube, and of course I can just go through the same procedure ever year or so.

 

[raleighnut]

In an idle moment I decided to take a hammer to a new (in my new spares drawer) NECO bottom bracket cartridge (very similar to UN300). After removing the LHS cup I opened the vice jaws and rested the inside of the RH cup on them - a very small tap with an aluminium alloy hammer and the axle fell out, leaving the sleeve and Rh bearing attached to the cup, and the LH bearing still on the axle of course.. No drama and nothing broken, I attacked the inner seal of the LH bearing with a metal scribe and managed to yank it off. The bearing had some grease in it, but I packed it full of grease. The RH bearing seal was a little more difficult to remove because the access was through the length of the sleeve, but the same packing was carried out. If I get around to using this BB I think it will last longer because of its extra initial lube, and of course I can just go through the same procedure ever year or so.

Adding a few drops of a thin oil (3 in 1 or similar) refreshes dried up grease easily