Bottom Bracket completely worn out 3 times in 6 months

shongololo

My wife's Cannondale CAADX bottom bracket (BB30) was in pretty bad shape in February, so she had a bike shop replace it.

About 2-3 months later the bottom bracket was completely done-in again. She took it back and they replaced it again, saying that the part should have lasted longer.

Another ~3 months later it is completely shot-through again. This time they charged her and said that the shaft attached to the crank (FSA Gossamer) is 'rough' on one side, and that this roughness is what is destroying the bearings.

Her daily commute sums to about 10km, so it is relatively light usage - maybe 500km between the bottom brackets giving out, certainly no more than 1000km.

Is this a 'thing', where the shaft somehow becomes pitted or otherwise builds up an accumulation of grime that causes the bearings to disintegrate? Is there a way to resolve this (cleaning?) or does one have to buy a new crank?

Thanks.

meanredspider

Personally I'd buy a BB converter to allow you to run a different BB system like Hollowtech II

It maybe that you have alignment issues in the frame that mean that the bearings are getting killed. It will mean running different cranks but at least your wife can get on with riding the bike.

wongataa

shongololo wrote:

Is this a 'thing', where the shaft somehow becomes pitted or otherwise builds up an accumulation of grime that causes the bearings to disintegrate? Is there a way to resolve this (cleaning?) or does one have to buy a new crank?

Sounds like cobblers to me. The outer race of the bearing shouldn't move relative to the frame. The inner race should not move relative to the crankset shaft. The balls in the bearing do the actual rotating allowing the shaft to spin. When the balls degrade or the parts of the bearing the balls run against degrade that's when you get noise and a crunchy/lumpy feeling when the cranks turn. If the shaft is a bit rough it shouldn't matter. You could always take the crankset off and see what the shaft looks like for yourself.

Monty Dog

The reason the crank spindle is rough is probably down to the bearing seizing and the spindle turning within the inner bore. The problem is that BB30 is a bit of a crock, particularly if the bike is ridden in the wet without mudguards - spray from the rear wheel gets down the seattube and settles in the BB shell - the bearings are now immersed in dirty water and don't last very long. The problem is Cannondale and their ilk don't inform the owners as it's effectively an admission that it's not really fit for purpose for riding in the rain without mudguards. Fitting an adaptor BB and a 24mm spindle crank helps because at least the bearings are slightly better protected, as would fitting a rear mudguard.

Ben6899

I have one BB30 frame and I have fitted the Rotor conversion kit, to run a DA crank. Touch wood, it's been fine since this.

shongololo

I removed the cranks tonight and noticed the slightly roughened area where the bearings probably siezed at some point. But it is still quite smooth and doesn't seem like something that would cause new bearings to fail because it rotates with the inner bearing sleeve.

What I did notice is that there is nothing protecting the bearings, just the wavey washer. Looking at installation instructions, there is supposed to be a bearing shield, which would make sense. My current hypothesis is that the bike shop misplaced the bearing shield and water is free to get straight at the bearings...

sungod

there should be a shield each side, whoever fitted them got it badly wrong if there're no shields, these press against the inner race each side, without shields there'll be no sideload or the'll have bodged it with spacers

well maintained i'd expect a set of bearings to last years and/or 10,000-20,000 km depending on conditions, certainly mine do and they have plenty of wet rides, but cannondale don't seem to be that good on bb shell quality

find another shop with a mechanic who can do it properly or diy, it's not difficult, packing the bearings with grease will extend life, new ones are usually lightly loaded and sometimes with grease that's easily flushed out, i use a waterproof/marine grease, it lasts ages

the sram bearing kit comes complete with shields, washer and shims