Wear cup & cone bottom bracket [pics]

slidetaker
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Wear cup & cone bottom bracket [pics]

Postby slidetaker » Tue Apr 30, 2013 10:26 am

Hi folks,

Pulled apart a cup and cone BB from a late 80s mountain bike. It was still smooth to turn by the tips of fingers, but some play was noticable when holding the crank and pushing in/out.

Most ball bearings have minor chips like these two.
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This is the worst one. Some deformation. :shock:
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The spindle bearing faces were also scarred at both ends.
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The adjustable cup has a very shallow ridge developed which is barely showing in the below pic. :)
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Is it fair to say the balls worn the worst with spindle closely followed while the cups seem to hold up pretty good.
Do other people have simimlar wear rate and pattern when they worked on worn BB??? :?:

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QuangVuong
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Re: Wear cup & cone bottom bracket [pics]

Postby QuangVuong » Tue Apr 30, 2013 1:46 pm

Were the cups on too tight, or too loose? Ive had balls that were worse off(half worn to an oval shape) in the wheel hubs, which made a clicking noise. Only the balls were worn. The cups and cones werent too bad.
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slidetaker
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Re: Wear cup & cone bottom bracket [pics]

Postby slidetaker » Tue Apr 30, 2013 3:51 pm

The adjustment was just right. Maintenance has obviously been neglected. Play was then further developed and wear rates were accelerated.

Yes I am seeking for other people experiences. So far, researches and empirical evidences show the ball bearings and spindle were the weakest link.

It is interesting to note that the wear pattern on the bearing races of the spindle is different from the cups, although they both have similar contacting surfaces with the balls.....

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QuangVuong
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Re: Wear cup & cone bottom bracket [pics]

Postby QuangVuong » Tue Apr 30, 2013 4:46 pm

Difference in wear would be due to the different materials. The balls are softer than the cups and axle(cone), to have a reduction in total wear. The balls will wear away without destoying the cups and cones, and they are much more easily and economical to replace.
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rustychisel
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Re: Wear cup & cone bottom bracket [pics]

Postby rustychisel » Tue Apr 30, 2013 6:41 pm

QuangVuong wrote:Difference in wear would be due to the different materials. The balls are softer than the cups and axle(cone), to have a reduction in total wear. The balls will wear away without destoying the cups and cones, and they are much more easily and economical to replace.


true that.

In my experience - going back to the 1970s - the wear is always to balls, spindle, then cups, in that order.

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Mulger bill
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Re: Wear cup & cone bottom bracket [pics]

Postby Mulger bill » Tue Apr 30, 2013 7:11 pm

Yeah, that's borked.

The cup looks fine for re use tho'.
...whatever the road rules, self-preservation is the absolute priority for a cyclist when mixing it with motorised traffic.
London Boy 29/12/2011

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sturmey archer
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Re: Wear cup & cone bottom bracket [pics]

Postby sturmey archer » Fri May 03, 2013 10:16 pm

I'm inclined to think that the cup cones and balls have only been keeping the spindle in place. The shiny ring around the spindle makes me think it was running as a plain bearing on the outside of the cup - ouch!

Although the cups are normally the last thing to wear I can't think they're really still ok when the balls looked like that . Run the point of a pencil around where the balls roll. You'll feel any pitting.

Cup and cone BBs are rebuildable, traditional and a source of hours of entertainment :roll: while adjusting the lock ring for that perfect clearance. For character building they're only second to cottered cranks.
Personally I chuck 'em in the box of broken bits and put in one of those cheap, ugly, nasty cartridge bearings and forget about it!
1.370" x 24 tpi - what sort of stupid standard is that?

slidetaker
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Re: Wear cup & cone bottom bracket [pics]

Postby slidetaker » Mon May 06, 2013 1:43 pm

Good pick up on the shiny ring around the spindle. It looks to be created by deformed ball bearings....

I had another idea about the very shallow pitting on the cups. If the pitting is very similar in depth and very consistent along a certain circumference on the cup race, with new balls and new spindle, the BB should still runs very smooth and centre. The pitting may create greater contacts with the ball bearings as they are slightly embedded into the race.

Downside is greater drag. Upside is more material supporting the load reducing wear. Am I remotely correct in theory??? :!: :?: :?:

Going back to the pitting, depending on how much preload you put in the adjustment, the pitting location will vary. See below link regarding the theory.
http://pardo.net/bike/pic/fail-008/000.html

I find this strangely fascinating....otherwise I would have spent $12 sealed cartridge BB and watch some TV. 8)

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