Lately, I've been having trouble with my M3L's handlebar rotating forward in its clamp whenever I go up the sloping curb of my driveway. Whenever this happens, it prevents me from completely folding the bike (my stubby bar ends hit the brake track, rather than squeaking by the tire). It doesn't seem like my taking the curb is overly abusive, either (walking speed with a 140 lb rider), so that's another source of concern.
So far, I've tried degreasing the clamp area with isopropyl alcohol, shimming the clamp with aluminum, and Loctiting the clamp bolt. Unfortunately, the problem has returned, despite all of these attempts at a fix.
Has anyone else had this issue? If so, have you found a way to get the handlebar to stay put?
Did you remove the clamp bolt and examine the thread? Do you know how much torque you're applying when you tighten it?
1) Yes: it does look like there's a bit of metal clogging the very start of the bolt's thread. Now that I think about it, I'm wondering if this may be stripping the clamp threads....
2) I do not know: I don't have a torque wrench. I do know that before I put the shim in, it seemed like I would have to twirl and twirl the bolt before it would tighten. Now, with the shim in, the bolt tightens much more positively after several turns.