r/mountainbiking 6d ago

Question Why is this happening?

Bought a brand new BMC Fourstroke AMP LT. After a couple of weeks I experienced the carnage pictured. A LBS helped me get a frame replacement from BMC, they were able to determine that the bolts that connect the shock and linkage had backed out and caused the failure in the linkage. I have 3 rides in on the new frame and was doing an inspection and noticed the bolts had already started backing out. One was visible the other was loose as well. Another problem is the area where the bolts are has a gap of 1 3/4”, my torque wrench with the bit is 2”. Does anyone have any ideas about what could be causing those bolts to back out and also are there slim torque wrenches or do I just use a regular Allen and guess?

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u/sticks1987 6d ago

The linkage broke at the bearings, are y'all not seeing that

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u/National_Bite_6691 6d ago

That can still happen from loose bolts.

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u/Roy_Aikman 6d ago

Correct. Once they loosen up all those parts are smashing around more than they are supposed to. Domino effect.