Originally Posted by
phtomita
Hello,
I have a Nishiki Tri-A frame built with modern components and my handlebar rotates forward when I put more weight on tops.
It happened recently when I found a snow/ice patch on a trail and found myself balancing and to get through, but walked most of the parts
.
And recently when I climbed some standing up.
I can loosen and tight back to the position I want, but this keeps happening few times now.
The size of quill stem and handlebar are for 25.4mm, so it is not an unmatched size issue.
Any suggestion/opinions are welcome.
In addition to the good advice already given you can rough sand the clamping section of the bar and use carbon gripper paste too.
The bar clamp of the stem is key here if it is closing all the way and not getting tight enough, something is amiss.
Not all marked parts are always what or as they seem, someone could have clearanced the bar clamp of the stem and the bar has probably been ground down from slipping so won't hold, too small anymore.
One or both could have been mismarked or incorrectly sized but sounds like you may have measured already.
Shims can be fussy but often do the trick.
