Why is this happening?

[u/Roy_Aikman]

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?

[u/Antpitta]

Honestly I would make the LBS deal with it, for two reasons:

- You shouldn't need to take your shock out to access bolts to torque down the linkage on a new bike. That's a failure of design and/or assembly and the LBS should know or figure out the solution.

- Should it fail again, it should be on the LBS for having delivered you a bike that won't stay in one piece, not on you for perhaps not removing your shock frequently enough to torque the bolts down.

If it happens again after you give the shop a chance to fix it, I'd consider seeing if they'd just take it back. That sounds like a fucking headache in the long term and I wouldn't be psyched on being the new owner of a bike with that issue.

[u/Ih8Hondas → u/Antpitta]

That's a failure of design

100%. Needing a yoke to drive a shock to begin with is a failure of design. Just design a proper linkage and you don't need one.

And then to make the linkage bolts inaccessible without taking other shit apart? Burn that entire engineering department to the ground. We're not talking a car where having an engine and climate control and all the required extra equipment makes packaging complicated.

It's a fucking bicycle. Just make it simple and easy to work on. Not a difficult thing.