# How long do bottom bracket bearings usually last?



## Treker

I'm just curious how long bottom bracket bearings usually last. I have a 2006 Trek 2100 with about 4,000 miles on the stock bottom bracket. Should I be considering replacing it at a set interval? 

I don't know if it makes much of a difference or not, but I am a big guy (6' 5 1/2", 205 lbs), so I assume that I am probably putting more stress on the bearings than a smaller and lighter guy would. However, I am also a spinner, and climb in the saddle most of the time, which I would assume would put less stress on the bearings than someone who does more out of the saddle climbing.

Thanks for you input!

Jay B.


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## FBinNY

It depends on too many factors to make any generalizations. Properly adjusted, and discounting weather related factors, all the bearings on a bike should last close to forever.

Back in the bad old days of "primitive" steel spindles and threaded cup bottom brackets, most would outlast the bike, or 25-50,000+ miles. However today's _superior_ cartridge bearing bottom brackets, especially those with outboard bearings don't seem to last as long, and many need replacing in the 5-10,000 (or less) range. That's progress.

Simple rule is (unless you're starting a long trip) "if it ain't broke don't fix it". Do normal maintenance, keep things properly lubed and your BB should last for another 4,000 miles or more.


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## AJL

FBinNY said:


> Back in the bad old days of "primitive" steel spindles and threaded cup bottom brackets, most would outlast the bike, or 25-50,000+ miles. However today's _superior_ cartridge bearing bottom brackets, especially those with outboard bearings don't seem to last as long, and many need replacing in the 5-10,000 (or less) range. That's progress.


Man, that suxs. I just installed some outboard bearings (HT II) for a Shimano R700 compact crank  No wonder I never had to replace anything on my "primitive" bikes. I just cleaned them once a year (with gasoline!) and repacked the bearings with Teflon or maritime grease. Yay for progress, NOT!


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## jmlapoint

My 'primitive' Campy Record tapered-spindle and cup/balls BB is still going strong from 1975.
Never wet, and I overhaul it every couple a years.
Change is good, but not all progress is forward.

John


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## Kerry Irons

*String theory*



Treker said:


> I'm just curious how long bottom bracket bearings usually last. I have a 2006 Trek 2100 with about 4,000 miles on the stock bottom bracket. Should I be considering replacing it at a set interval?


Your question is about like "How long is a piece of string?" The weather you ride in, how well your frame was built/prepped, and the quality of the BB will be big influences. If I had to replace BBs every 4K miles, I'd be doing it more than 2X per year. My last BB (Campy Record square taper) lasted 60K miles before I screwed up the install and cracked the flange on the RH cup - the bearings were just fine. My current (Campy Chorus square taper) has nearly 58K miles with no signs of distress.

If you turn the BB axle with a light touch of your fingertips (cranks off) and there is no binding or gritty feeling, then you're fine.


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## Richard

Part of the problem lies with the transition to "two piece cranks", with the bearing cups threaded onto the frame. When the industry went away from "cup and cone" loose/caged ball systems, facing a BB shell became a lost art. Square taper (and Octalink/ISIS) cartridge type bb's are far more forgiving of a bb shell that's slightly out of "face." The sealed cartridge bearings were "integrated" to the spindle, not to the frame. I had a Shimano UN72 in my old Bridgestone MTB last 10 years and it spun like new when I sold it.

But in our shop we see a lot of "two piece" cranks with problems, and that includes Sram, Shimano, FSA, even my beloved Campy. When those bearing surfaces are aligned by the BB shell, that shell must be absolutely "square." I've got a Campy UT and a Sram/Truvative/Bontrager GPX and both have been smooth as silk and wearing well, but I faced the BB shell before install (a steel Masi and a vintage Bertoni.)

That being said, the smoothest and slickest BB's in my stable are the Campy Chorus and the Stronglight square tapers in my old Falcon and Fuso fixie repectively.


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## boneman

*There are a lot of factors but for me*

It's been mostly about the riding conditions. I think Kerry pretty much points out the salient issues as well as the best way to determining if your BB needs replacing.

Like him, I have a number of BB's that have gone over 20k and a lot more miles w/o issue. This includes the traditional caged bearings and cups BB as well as the sealed. I'm glad to see someone else has separated the flange of a Campy sealed BB. I just got a little too enthusiastic on the install but obviously have since learned my lesson.

I just installed my first BB with outboard bearings, in this case a Campag UT. I bought a set of Chorus UT cranks used knowing it had a bad bearing (stock). I have the tools to pull and replace so with with replacement bearings cheap, it was worth buying. As for bearing life, we shall see.

The last 11 years have been ridden in very mixed conditions, lots of rain/wet and entirely on Phil, Shimano and Campag cartridge units. About 7,000-10,000km/year and no BB issues. My current location, Singapore, is excessively humid and corrosion/rust will no doubt be an issue. I've had to pay more than normal attention to lubrication and water issues than I have in the past but I don't expect it to be worse for the cartridge BB's although I can see the potential for outboard bearings having a shorter life. We shall see..




Treker said:


> I'm just curious how long bottom bracket bearings usually last. I have a 2006 Trek 2100 with about 4,000 miles on the stock bottom bracket. Should I be considering replacing it at a set interval?
> 
> I don't know if it makes much of a difference or not, but I am a big guy (6' 5 1/2", 205 lbs), so I assume that I am probably putting more stress on the bearings than a smaller and lighter guy would. However, I am also a spinner, and climb in the saddle most of the time, which I would assume would put less stress on the bearings than someone who does more out of the saddle climbing.
> 
> Thanks for you input!
> 
> Jay B.


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## Mr. Versatile

The Campy Chorus square taper BB that was on my DeRosa lasted ~ 60,000 mi before I moved them to my commuter.


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