You mean the steerer tube. Correct, you can run spacers above the stem temporarily while you dial in the fit. But you should cut off the excess steerer tube once you confirm your fit.
I believe the compression plug is not designed to have any spacers above it. I don't remember the exact reason but there's a strongly worded warning in the Specialized instructions about it. Other manufacturer's use a different type of expander plug which does not have this restriction.
The reason is because the greatest stress on a steerer is the interface between the bottom of the stem clamp and the carbon steerer tube. When torqueing on handlebars when sprinting, the bottom edge of the stem clamp creates a stress riser trying to shear the carbon steerer. The expansion plug reinforces this area. Spacing the compression plug upward raises the bottom edge of the plug which removes support of the plug under the highest stressed area.
Hope that helps.
A picture of the plug below:
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Road Bike, Cycling Forums
5.4M posts
205K members
Since 1990
A forum community dedicated to Road Bike owners and enthusiasts. Come join the discussion about bike parts, components, deals, performance, modifications, classifieds, troubleshooting, maintenance, and more!