jefmcg
Guru
Data point. My FSA bb that came OEM on my giant bike lasted a little over 13,000km. Ridden in all conditions, and completely submerged at least once. That was not a good day 
Bottom Bracket Lifespan
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NormanD
Lunatic Asylum Escapee
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- Heworth the other side of life!
30,000 miles??? ...I use BB30 and measure the life span in minutes 
Moodyman
Legendary Member
The Shimano Square taper on an older bike did circa 12k miles and was still butter smooth when the bike was stolen.
The Shimano Hollowtech on the current fleet last around 2-3k miles - used everything from a tiagra to Ultegra. Timeframe doesn't improve with more expensive ones.
In that 2-3k miles I also do a strip every 7-800 miles to top up the grease. I think with Hollowtech there are two reasons they don't last - one the bearings are ridiculously small for the kind of power put them through them and secondly the seal is not great and water gets in easily.
I think if didn't commute in all weathers they might last longer.
The Shimano Hollowtech on the current fleet last around 2-3k miles - used everything from a tiagra to Ultegra. Timeframe doesn't improve with more expensive ones.
In that 2-3k miles I also do a strip every 7-800 miles to top up the grease. I think with Hollowtech there are two reasons they don't last - one the bearings are ridiculously small for the kind of power put them through them and secondly the seal is not great and water gets in easily.
I think if didn't commute in all weathers they might last longer.
External bottom brackets were marketed as allowing larger bearings, but the ball bearings are usually small and radial in HTII BB's.
My singlespeed's bmx BB uses 6204RS sealed bearings with 5/16" (7.938mm) balls which last years even if neglected.
From http://www.slowtwitch.com/Tech/Bearing_Breakdown_2822.html:
"To make matters worse, some products use bearings that simply are not designed for the application. Remember that part about radial vs angular contact bearings? Well, some hubs and bottom brackets use radial bearings – which are only designed to take forces in the vertical plane. If you only ride your bike while seated, and never turn a corner, you’re fine. I don’t know about you, but sometimes I stand up, or sprint, or ride in such a way that is otherwise not a perfectly controlled laboratory condition. In effect, using a radial bearing in an application that will see substantial lateral loads assumes eventual failure. It is possible to help alleviate this issue by using a larger ball bearing size – this “gifts” the design extra load capacity, so it will last somewhat longer. But unfortunately, bearings are the heaviest part of the hub – so more bearing means more weight (which doesn’t help sell product)."
My singlespeed's bmx BB uses 6204RS sealed bearings with 5/16" (7.938mm) balls which last years even if neglected.
- Cup and Cone BB bearing size:_______1/4"___(6.35mm)
- Shimano Cartridge BB bearing size:____7/32"_(5.56mm) and 5/32" (3.97mm) (TY-30)
- Hollowtech II BB bearing size:_________1/8"__(3.2mm) (Tiagra)
From http://www.slowtwitch.com/Tech/Bearing_Breakdown_2822.html:
"To make matters worse, some products use bearings that simply are not designed for the application. Remember that part about radial vs angular contact bearings? Well, some hubs and bottom brackets use radial bearings – which are only designed to take forces in the vertical plane. If you only ride your bike while seated, and never turn a corner, you’re fine. I don’t know about you, but sometimes I stand up, or sprint, or ride in such a way that is otherwise not a perfectly controlled laboratory condition. In effect, using a radial bearing in an application that will see substantial lateral loads assumes eventual failure. It is possible to help alleviate this issue by using a larger ball bearing size – this “gifts” the design extra load capacity, so it will last somewhat longer. But unfortunately, bearings are the heaviest part of the hub – so more bearing means more weight (which doesn’t help sell product)."
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D
Deleted member 1258
Guest
The Pearson fixed I've just retired has a UN54 bottom bracket installed that has been in there for years and still spins smooth and free, the original ISIS bottom bracket the bike came with wouldn't last a a year before it needed replacement, I've just brought a Genesis Flier, its only done 400 miles and the bottom bracket is grumbling under load already, it seems to me that there a huge variation in longevity between bottom brackets depending on type and use.
