How long should a bottom bracket last?

[HLaB]

New one fitted today (couldn`t be bothered to moan about the old one at the shop), bike is transformed. Amazes me how something so small, in the scale of things can make cycling miserable. I hate uninvited noises, my bikes have to be silent or I`m out of here!! As a result I have got good at finding odd noises over the years, and I won`t give up until I do.............

The give away for me to BB failure is a sore hip, I'm amazed too how something small scale sets the hip off.

 

[iateyoubutler]

The give away for me to BB failure is a sore hip, I'm amazed too how something small scale sets the hip off.

I`m not surpised, for me it`s a 5mm change in saddle position for hamstring trouble

 

[keithmac]

I had 3 bottom brackets in my old Dawse Edge XT, bought the more expensive ones expecting better longevity..

Someone mentioned might be worth giving a cheap one a go so I did, it was marginally heavier than the more expensive one but lasted as long as I had the bike after fitting (much longer than the expensive ones..).

I think they were sealed Shimano square taper BB's but was a long time ago!.

What make bearing cartridges do the Shimano BBs use?, on the motorbikes I've found Koyo or SKF to be most reliable..

 

[iateyoubutler]

I had 3 bottom brackets in my old Dawse Edge XT, bought the more expensive ones expecting better longevity..

Someone mentioned might be worth giving a cheap one a go so I did, it was marginally heavier than the more expensive one but lasted as long as I had the bike after fitting (much longer than the expensive ones..).

I think they were sealed Shimano square taper BB's but was a long time ago!.

What make bearing cartridges do the Shimano BBs use?, on the motorbikes I've found Koyo or SKF to be most reliable..

Not sure on the actual make, should have looked before I fitted it....doh!!

 

[andrew_s]

What make bearing cartridges do the Shimano BBs use?, on the motorbikes I've found Koyo or SKF to be most reliable..

I'm led to believe that they don't - the bearings run directly on the axle.

You can get SKF square taper BBs if you look hard enough, which used to come with a 100,000 km no quibble guarantee (I think it's 10 years now). The problem was that they cost about 5 times what a UN5x did, and even 100,000 km isn't 5 times the normal life of a Shimano BB.

 

[keithmac]

Just had a google and they are quite expensive (£130?).

Maybe riding style has something to do with BB longevity, more time out of the seat standing on the pedals will put more stress on the BB.

 

[Hedgemonkey]

Just had a google and they are quite expensive (£130?).

Maybe riding style has something to do with BB longevity, more time out of the seat standing on the pedals will put more stress on the BB.

That was my theory too, on top of the horrible conditions from winter riding, I do tend to big ring and honk up the climbs instead of spinning, yes I know spinning is more effective, but then the climbs seem to take soooooo much longer.

 

[iateyoubutler]

That was my theory too, on top of the horrible conditions from winter riding, I do tend to big ring and honk up the climbs instead of spinning, yes I know spinning is more effective, but then the climbs seem to take soooooo much longer.

That might be what killed mine. My ride home every evening has an 8 mile stretch uphill and I try and try to do it faster than the day before, and it`s always done in the big ring. Perhaps I don`t know my own strength!

 

[Tim Hall]

except dirt and water get in between the bearing cassette and the bottom bracket and the cassette doesnt have a good fit so it act like a grinding paste and grind away at the frame. Oh and the water gets into the bearing and they seize up.

and thats why trek brought out oversized bearings to try and stop it happening

Your terminology is confusing. What/where is the "bearing cassette"?

 

[Lee_M]

Your terminology is confusing. What/where is the "bearing cassette"?

is it really or are you just being an arse.

try google and it will take you to exactly what we both know I'm talking about

 

[Tom B]

If it makes you feel any better I've just got through a square taper bb in about 4 months and a previous unit after 6months.

I put it down to my using sunrace units (though they have fsa bearings) and crappy conditions. The original Shimano un26 lasted 3years.

I ride everyday and commute on Northwest roads that are regularly salted, my front guard has lost its spoiler and I've not got around to replacing it. This means crappy salty water is thrown up onto the bottom 3" of the downtube and around the bb. I also rude the bike in lots of muddy gritty stuff.

The last unit failed giving no real noise, no wiggle but mainly lateral float, sufficient to start affecting shifting. Once removed I found it typically sloppy, rough and noisy between the fingers. With one of the bearings rotating on the edge of the unit.

After seeing yellow saddles recommendations on another thread I bought a un55 bearing. Appears to be better sealed around the shift.

Other than putting the cranks on wonky, you can't really mess up installation of this kind of bb can you?

 

[Tim Hall]

is it really or are you just being an arse.

try google and it will take you to exactly what we both know I'm talking about

Yes it is, but I'll not bother thanks.

 

[Yellow Saddle]

What make bearing cartridges do the Shimano BBs use?, on the motorbikes I've found Koyo or SKF to be most reliable..

It is a proprietary cartridge bearing made for Shimano, probably by one of the Japanese manufacturers. I say proprietary because, if you look at the number stamped on the bearing (It's been a while and I'm rusty, but perhaps 6085?) and you look up the nominal dimensions of a 6085(?) you'll notice that the Shimano bearing is 1mm narrower than what it is supposed to be. Bearing numbers are SI numbers that dictate specific dimensions so the number on the Shimano cartridge is a decoy. If you buy the same bearing you'll end up with a bearing that's too wide.
They don't run directly on the axle. There is a plastic bush between the cartridge and the crank spindle.

 

[Yellow Saddle]

except dirt and water get in between the bearing cassette and the bottom bracket and the cassette doesnt have a good fit so it act like a grinding paste and grind away at the frame. Oh and the water gets into the bearing and they seize up.

and thats why trek brought out oversized bearings to try and stop it happening

I'm not sure what you mean. Dirt cannot get in between the cartridge and the BB spindle because it is pressed into a nylon bush that sits between the two. Only on BB 30 do you have the cartridge inner race making contact with the spindle.

Trek didn't bring out an oversize bearing to prevent dirt getting in there. The BB30 consortium lead by Cannondale at the time invented BB30 to counter BB axle flex (the real cause of left hand bearing failure) but failed miserably though poor assumptions and stupid engineering.

 

[keithmac]

It is a proprietary cartridge bearing made for Shimano, probably by one of the Japanese manufacturers. I say proprietary because, if you look at the number stamped on the bearing (It's been a while and I'm rusty, but perhaps 6085?) and you look up the nominal dimensions of a 6085(?) you'll notice that the Shimano bearing is 1mm narrower than what it is supposed to be. Bearing numbers are SI numbers that dictate specific dimensions so the number on the Shimano cartridge is a decoy. If you buy the same bearing you'll end up with a bearing that's too wide.
They don't run directly on the axle. There is a plastic bush between the cartridge and the crank spindle.

I've seen this a few times when rebuilding 2 stroke motorcycle enigines, although the original crank bearings have the 4 digit bearing number stamped on them the replacements are too wide.