Bought and fitted a new crankset with Deore external bearings around 2 months ago. The grinding and crunching sounds started after around 2 weeks. Now there is rusty brown fluid dribbling from the non-drive side. It’s barely rained since I fitted it, I haven’t ridden it through standing water, and I’ve washed the bike twice with a low pressure garden hose (avoiding the bearings as far as possible). Until now I have fitted Octalink and before that square taper and used to get 1 – 2 years trouble-free life from them.

I know I will be berated for not having the BB shell faced but should that result in such an early failure? If so, surely the design is at fault: we’re talking mountain bikes here, not micro-surgery. The design should allow for normal manufacturing tolerances, shouldn’t it?

Anyone else seen a similarly early failure, and can someone recommend an alternative bearing which has some durability, please?

Deore here, get 12 months out of them easy.

Its a bit late for you now, but I always take the top hats and the outer bearing seal off new BBs and fire a load more grease in there, keeps the water out and generally enhances their life expectancy.

Thanks bigyinn, I might just give that a go!

There’s something wrong there. Crunching after 2 weeks?? Either you’ve done some epic rides in those 2 months, it was fitted wrongly / your BB shell is waaay off or you’ve let GT85 / WD40 or similar get near the bearings?

That not my experience of them, most definitely in the case of the last one I fitted, at least a year old & still going strong.

As for replacement’s unit, I’ve yet to have any one convince me that the it’s worth spending more on anything, than Shimano.

I get a good year out of mine, XT lasts a bit longer but there’s not much in it IME

Deore cranks bought in the summer and still running smoothly on Mrs Hooter’s touring bike after about 1000 miles, including some very wet autumn days…

Get hope next time, mine are still going strong after 1000’s of miles (with the occasional regrease every few months).

I’ve had deore and XT BB’s before, they’ve lasted a few hundred miles before seizing.

How tight did you do up the plastic preload cap when you installed it?

Killed one once in 2 rides by over tensioning the preload cap.Rpelacemnt was fine and still is when correctly tensioned.

Coatesy – nail on head there.
Most people do things up way too tight. Side loading on a bearing=death to balls and cups…

I had one, (Shimano Deore) lasted about a year. Which I though was fine.
I replaced it with a nice goldy blingy one from Superstar in May.
I’ve now gone back to Shimano, after two warranty claims and an accusation from SS of crossthreading their BB! Two sets of angular bearings seized in as many months! 😆

Mine didn’t last too well, 6 months or so in winter… Not bad, but maybe half as good as an XT- seals just aren’t as good.