CARTRIDGE BOTTOM BRACKETS, brilliant aren't they
- Thread starter srands
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My pals seem to have had nothing but trouble with external BBs on road bikes. I shudder to imagine the lifetime on MTBs with all that mud.
Cartridge BBs are OK and I have a couple of UN72 which have lasted over 20,000 miles. However, to get it all to fit in a cartridge the bearings are smaller than a cup and cone, which has 11x 1/4" balls. That's fine on a solo bike, but tandems have much higher bearing loadings and cartridge BBs only last a couple of thousand, whereas the cup and cone ones last longer in terms of bearing wear.
Cartridge BBs are OK and I have a couple of UN72 which have lasted over 20,000 miles. However, to get it all to fit in a cartridge the bearings are smaller than a cup and cone, which has 11x 1/4" balls. That's fine on a solo bike, but tandems have much higher bearing loadings and cartridge BBs only last a couple of thousand, whereas the cup and cone ones last longer in terms of bearing wear.
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That's why they turned to external againhamster":3pmx38dd said:
Moving to ISIS/Hollowtech(Octalink) made the cartridge system strain even further as the shaft got thicker balls shrank.
So they moved them outside to use bigger balls or made them fit in the frame itself (BBxx stuff, way to modern for me to bother to know it's name)
I must say though, I'm disappointed as my original UN90 has started to get some play, still very smooth running though.
BB30 was also another approach, with the advantage of the bearing shells getting some support from the frame, unlike external. However, I've heard a couple of disappointing stories about BB30 too. It amazes me, surely such a bearing would be well-understood by now and after a century people would be able to make a durable one? :?
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hamster":113e6zxd said:
I'm guessing they could just increase the shell size? (them adjustable single speed ones for example. Though knock on effects with taking up more room behind the frame, unless you shape them.
The problem I see with HT-II and if BB30 takes the same approach, is the same problem with cartridge bearings in hubs etc and they can so easily be overtightened to displace the two races in the cartridge. At least with cup'n'cone old 'rubbish' setting it was easy and it didn't damage everything so much.
I guess bearing style type and some cartridges may be made to have a similar behaviour to cup'n'cone side loading.
One for me not to worry about though.
