Bicycle Mechanics - How long should a bottom bracket last?

I am surprised that the cartridge bottom bracket on my mountain/urban bike has only lasted about 5,000 Km. :notamused:

It started making clunking noises so I have replaced it with a Shimano unit.

The original is branded Neco and I believe that that they are made in Taiwan.
Perhaps this brand is a bit suspect? :crash:

As I live in a farming area, the land around here is like a billiard table, so I have not done any hill-climbing, at all.

I admit, that I cycle to keep fit and always use the highest gear possible, so that I have to work all of the time. This means that there is always quite a bit of pressure on the drive train.

Perhaps this practice has contributed to the premature failure?

I'd be very interested to hear comments.

Regards,
Roger :)

how long they last depend on the riding conditions, rain, dry, dusty etc. no real way to put a number to it

Riding in the highest gear possible will NOT make you more fit. If that were true you would see racing cyclists pounding around in 100+ inch gears all the time turning the cranks at 50 rpm. That being said, unless you are out of the saddle in a high gear and low speed a lot, cranking a high gear will not wear the BB that much (though it will chain and gears). The bike will just sway more in response to the off-center stress of pedaling too high a gear.

Probably grit from those ploughed fields , just get another replacement part,
and You would be wise to overhaul your wheel hubs , and headset bearings to replace
contaminated grease..

I added O rings on the BB axle endsto gain another seal, when I pressed them against the outside
of the BB cartridge shell's ends when I put the crank arms back on..

My police patrol bike is about 15 years old and still has the original cartridge BB in it. I spin a lot.

I have a $70 fsa isis bb on one bike and a $12 nashbar bb on another. They both appear to have been made by the same company and riding the bikes, I can't tell a difference. But I can replace the $15 one 5 times over before it costs the same as the.fsa. it would be annoying to do but it really doesn't take that long nor is.it that tough of a job.

I am surprised that the cartridge bottom bracket on my mountain/urban bike has only lasted about 5,000 Km. :notamused:

I admit, that I cycle to keep fit and always use the highest gear possible, so that I have to work all of the time. This means that there is always quite a bit of pressure on the drive train.

Perhaps this practice has contributed to the premature failure?
A properly maintained, high quality bottom bracket can last a lifetime. But obviously many bottom brackets fall short of this.

It is highly unlikely that pedalling in high gear will cause premature wear. More likely lubrication failure and/or contamination are the culprits.

BTW, pedalling in high gear will not make you more fit, but it will put more stress on your joints which is not a good thing.

How long should a bottom bracket last is sort of a loaded question.

It used to be they lasted nearly forever, but most modern BBs don't last that long. Reduced weight has increased deflection, which increases wear, and the cartridge bearings used can't be field stripped and rebuilt the way the old cup and cone systems could. The real enemy isn't wear per se, but wear compounded by the effects of dirt and weather.

Bottom bracket is dependent on so many things that it is hard to say how long one will last... I seem to be getting 15000 - 20,000 km out of Shimano cartridge bottom brackets but am pretty light and spin more than I mash.

My old cup and cone bottom brackets seem as if they will last forever with regular service.

Have been test piloting some of these Neco bottom brackets and have not experienced any issues with them... they use a standard sealed cartridge unit and run out quite smoothly.

I'd certainly think any BB should last far more than 5,000km - perhaps yours was flawed in some way / QC miss, etc.
Anyway, replace it and ride on!
Oh, and you might want to read up on fitness cycling before you blow out a knee by mashing a big gear all the time. =)

My FSA MegaExo external BB has 27,000 miles on it and still seems okay.

My FSA was done at 18,000 miles

Thanks for the comments, guys!

I guess that it was just a faulty BB.
I don't think that the dust from the farming here is an issue, as I always pack waterproof grease around the outside of the bearings, before replacing the pedals.
Using an 'O' Ring is a good idea, though.

I'm sorry but I may have mislead you in saying that I always use the highest gear possible.
Yes, I do, but not to the point of mushing all of the time.
As I said, it is fairly flat around here and using the 11-tooth cog allows fairly easy cruising.
I do have to put in a bit of effort of course, but I'm nowhere near the point of putting myself in danger of injury.

Again thanks for the comments.

Regards,
Roger

My FSA was done at 18,000 miles

See, more proof that I'm just not a very strong pedaler. :D