Old 07-01-19, 08:46 PM
  #25  
Kimmo
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Originally Posted by Dave Mayer View Post
I am looking at a row of uncut forks with carbon steerers. The wall thickness of these is such that it would take immense compressive forces to crush these. Far far beyond what is reasonably necessary to hold a stem onto a fork steerer.

A well designed carbon steerer should NOT need internal reinforcement to counteract the clamping force of the stem. That would be a very poorly designed system, as there are all different forms of stems and expander plugs on the market. The chance for mechanics swapping parts, or installing the expanders in different ways over the life of a fork is basically 100%.
Haven't you seen deformed carbon parts, including steerers? I wouldn't say it's quite normal, but it's definitely fairly common, IME. It's just plastic, after all. Without a robust expander plug, the steerer can end up effectively tapered if there isn't a bit poking out of the top, neatly explaining the 5mm above precaution. That's why when I cut my steerers flush, not only do I use a good, well-positioned plug, I also tighten the bottom clamp bolt a tad more.

My theory about the deformation is that it isn't necessarily caused by overtorque, but can happen as a result of normal clamping pressure and riding loads, plus enough time. Heat cycles, too, maybe?
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