Hollowtech II pinch bolts self loosen

[oldpotatoe]

Originally Posted by tctyres

I didn't use my torque wrench. They are very tight. I can take another look at this.

I don't recall ever having used a torque wrench, however. I have 3 bikes with Hollowtech II cranksets, and I've had zero issues over the past 5 years. This is the first time this has come up. It's odd.

I agree that it sounds like something else is going on.

First that 'cap' is just for installation, not for 'security'. Second, if they are 'really tight', I wonder if you have deformed or 'wallowed' the crank arm to spindle to the point were they won't stay tight? That's why that wee plastic 'plate' is in the crank arm 'slot' to prevent this(part 4), to prevent over tightening and deformation...BUT yup, blue loctite and a torque wrench is a good idea.

[tctyres]

I finally got around to taking a look at this and inspecting everything.
Here's a quick update:
There are no cracks.
There is plenty of grease/scuzz on the bolts. (Part 3) They were definitely not at the same torque, and one was well below torque spec.
Both bolt washers were in place.
The crankarm fixing bolt was missing. (Part 1) I think this was because it was loose, and it came off in transit. TSA inspected the bag, and I'm certain that bolt was on prior to travel.
I don't like the play in the bottom bracket.
Both the shim on the bb and the washer (Part 5) were in place.
The grooves on the spindle and the crankarm look fine.

The crankarm loosened a second time because I did a road fix the first time but did not follow up.

So, I think the steps are replace the bottom bracket, replace the paper clip part (#4), clean everything, and use blue loctite.