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ashwinearl said:
i'd say they were either loose or you torqued them too hard when installing them. i use my al-bolts since 5 years and never had them fail. BUT i had the exact same thing happen when installing a new ring and putting too much torque when thightening the bolts.
pedaling forces don't make the head tear , they would rather shear the bolts.
 

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thats not true....

there is always a force on the bolt thru the center axis of
it, not just a shear force. under a load an alloy bolt could easily
fail this way, which is why alloy bolts are not recommended for
the granny gear.
 

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peabody said:
there is always a force on the bolt thru the center axis of
it, not just a shear force. under a load an alloy bolt could easily
fail this way, which is why alloy bolts are not recommended for
the granny gear.
well-
i'd say the bolts are not that much stressed tensionwise. the tension you torque them is all that's there. maybe a bit if you are running in a crossed gear but that's only minor. i'd say those bolts get stressed almost only from shearing forces.
 

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you could say

there are no forces thru the axis only shear forces, but you
would be wrong. the fact is there are ALWAYS reaction
forces, and they would put the bolt under tension. whether or not
you want to believe it is up to you. again that is why alloy
bolts are not used for granny gears
 

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Of course...

peabody said:
there are no forces thru the axis only shear forces, but you
would be wrong. the fact is there are ALWAYS reaction
forces, and they would put the bolt under tension. whether or not
you want to believe it is up to you. again that is why alloy
bolts are not used for granny gears
Of course in the real world, the bolt will face any number of forces on it. When properly installed, the only significant force that it will see is a shearing force. I'm sure it is not recommended for the granny because of the additional force that will be applied to it. In the end, the only way the bolt will see a non-shearing force big enough to do that is through improper installation.

Chris
 

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correct...

ctxcrossx said:
Of course in the real world, the bolt will face any number of forces on it. When properly installed, the only significant force that it will see is a shearing force. I'm sure it is not recommended for the granny because of the additional force that will be applied to it. In the end, the only way the bolt will see a non-shearing force big enough to do that is through improper installation.

Chris
end of the story.
 

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Hey ashwinearl, totally off topic but that bolt picture is actually quite good. It would make for a good desktop background image - something a little different but bike related.
 

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nino said:
end of the story.
I cracked a few that had been torqued to 50 in-lb. They didn't get that bad though, and I noticed the very small cracks during the bike's winter overhaul. I'm going to try 35 in-lb with the replacement bolts and see how that works.
 

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"Problem Solvers" brand bolts?

The quality of that brand is a bit hit and miss. The thickness of the flange on the head has varied on some that I have. I've had 2 or 3 crack just like that when tightening them. They may have developed small fractures during installation that didn't completely open up until later too. Be sure to lube them really well on the threads as well as any surface that needs to slide against another surface. Besides the few that I've broken, I have them installed on all my bikes, including small chainrings & even my singlespeed, without issues. I tighten them to 9 Nm (~80 inch pounds). I've had 1 inner bolt come loose at 8 Nm.
 
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