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Old 06-23-10, 05:34 PM   #1
douchebagonwhlz
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BB wear on spindle

On a BB spindle, is it normal to have the marks where the bearings rest on the spindle to be seemingly worn more on one side than another?
I have noticed this on a couple of spindles, is it due to the spot in the pedal stroke that recieves the most pressure? Could this be a precursor to pitting? or is pitting due to grit?
I am speaking of an old style cup and cone BB.
Sorry, no pics. Camera battery down.
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Old 06-23-10, 05:48 PM   #2
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It's totally normal. I would guess that the part with the most wear would be the right hand side, opposite the right hand crank arm, because it withstood chain tension during the strongest part of the pedal stroke.

It is a precursor to pitting, but it's also normal and the only thing you can do about it is maybe mark which way the crankarm was on the spindle, and reassemble it in a different position each time you service it, to spread the wear around.

You can't always swap right and left sides of the spindle because some spindles are asymmetrical.

Pitting is simply caused by the metal being stressed repeatedly. It gets hard and starts to crumble. There's nothing you can do about it except assemble your bb carefully, unless you want to lose a lot of weight and pedal gently just to save the bike. Wiki metal fatigue if you want to know more.
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Old 06-23-10, 06:47 PM   #3
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Most spindles are asymmetrical yet it can be inverted if the chainrings don't hit the chainstays but that is usually impossible (I've done it on a road bike but with a single chain ring that i moved it on top of the spider rather than the original on the back of the spider.. not for wear but for a smaller chainline)

For distributing the wear on the spindle you can install the cranks in difference position related to the spindle (180 degrees)
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Old 06-23-10, 06:56 PM   #4
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It eventually will happen but much more slowly if you don't grind high gears and keep the bearing adjusted properly. I've owned many cup and cone bottom brackets and generally find very little variation in the width of the bearing track on spindle or cups.
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Old 06-23-10, 07:04 PM   #5
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another fun solution for fixed gears only: flip the rear wheel, install the chainring crank and the chain on the left side

Or even a 2side drive like here:

And can even be a fixie with two freewheels without worry of coming loose, and the wear on the spindle would be constant on each side
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Old 06-23-10, 07:07 PM   #6
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I see, so I can rotate the spindle on the square taper seat in order "to keep things rolling." and big gear pushing is hard on the spindle. If the spindle is symetric then it can be flipped around so that the spindle gets pressure evenly.
thanks!
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Old 06-23-10, 08:25 PM   #7
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Actually, the small ring gives the most force because of the tremendous leverage, assuming you are climbing something steep enough to put some load on it.

If the load varies during the pedal stroke, as it surely does, it only stands to reason that it would be more worn at some points than in others.

It is controversial but I favor adjusting cup-and-cone bearings with a little bit of preload, just so you feel a very slight lumpy drag when you rotate the spindle or axle in your fingers, because it spreads the load over more balls. No preload lets the axle or spindle sag a bit under load, and then only one ball is taking most of the load.

Say, Asi, what do you mean to tell us by using the sign over Auschwitz as your sig?
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Old 06-24-10, 04:41 AM   #8
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Quote:
Originally Posted by garage sale GT View Post
Say, Asi, what do you mean to tell us by using the sign over Auschwitz as your sig?
offtopic:
It's just a reminder about history.. for me it matters. (and it's not the Auschwitz sign specifically.. any concentration camp had one). It's the irony in the message... (work makes one free)
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Old 06-24-10, 10:36 AM   #9
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It is important to preload the bearing upon assembly. Poor adjustment will cause pitting and excessive wear. You seem to have done the job properly.
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