Can confirm. I have one and I’ve only serviced mine once. It’s currently in my Japanese fixie. I even did a Japan tour using it. No idea what kind of black magic it is but it’s never going to die.
rhapsodyindrew on
The bearings do eventually wear out, and then you need to replace the whole BB because this model uses sealed cartridge bearings which are not intended to be replaceable.
I don’t think the sealed cartridge bearings on square-taper BBs are typically any more or less durable than on other BB styles like Hollowtech II, but maybe someone else has more info there. These bearings would be smaller diameter than outboard designs like Hollowtech II, maybe that makes a difference?
All else equal, I would think outboard bearings would last *longer* than bearings in traditional BBs like this one, because the outboard bearings are closer to the crank arm/spider, creating a shorter “lever” and reducing the force on the bearings. I’d love to hear from a mechanical engineer about this though.
blackdvck on
The bearings on these units can be removed and replaced as well .
It’s not that hard a job ,I think RJ the bike guy does a video on YouTube on it.
Ol_Man_J on
Age matters far less than mileage and condition. I’ve pulled the un51s out at the co op that were crunchy before, put in new and leaned against a shed for 20 years. The rust that got cleaned off shouldn’t have had an impact on the bearings anyway.
4 Comments
Can confirm. I have one and I’ve only serviced mine once. It’s currently in my Japanese fixie. I even did a Japan tour using it. No idea what kind of black magic it is but it’s never going to die.
The bearings do eventually wear out, and then you need to replace the whole BB because this model uses sealed cartridge bearings which are not intended to be replaceable.
I don’t think the sealed cartridge bearings on square-taper BBs are typically any more or less durable than on other BB styles like Hollowtech II, but maybe someone else has more info there. These bearings would be smaller diameter than outboard designs like Hollowtech II, maybe that makes a difference?
All else equal, I would think outboard bearings would last *longer* than bearings in traditional BBs like this one, because the outboard bearings are closer to the crank arm/spider, creating a shorter “lever” and reducing the force on the bearings. I’d love to hear from a mechanical engineer about this though.
The bearings on these units can be removed and replaced as well .
It’s not that hard a job ,I think RJ the bike guy does a video on YouTube on it.
Age matters far less than mileage and condition. I’ve pulled the un51s out at the co op that were crunchy before, put in new and leaned against a shed for 20 years. The rust that got cleaned off shouldn’t have had an impact on the bearings anyway.