Originally Posted by
znomit
Why are these a thing? They should be removed after tightening the stem bolts.
They serve no purpose when riding.
This. Unfortunately the rumor persists that it helps protect the fragile steering tube from damage.
One of several "
carbon is fragile and poorly understood" myths (apparently).
Originally Posted by
Kontact
In my experience the cap itself helps prevent creep of the stem that is tightened to only 5nm. It probably shouldn't work that way, but they do.
I haven't seen this stem creep/loosening of bearing preload, and I rode without a preload tensioner for several years.
5 N-m stem bolt torque doesn't sound like much, but it's more than enough to keep the stem from twisting under heavy torque, so it seems that it ought to prevent the stem from creeping up the steering tube. Might something else in the headset stack be moving/deforming? Bearing race on the fork crown, maybe?