Hey there!
Something is puzzling me.
I understand and am familiar with the consensus that we want the stem bolts around the compression plug on a carbon steering tube. Thus, a very minimum amount of spacers about the stem.
But now I look at my Trek Domane manual and I see this.
40mm max above stem. That's longer than the compression plus which, by design, always sits flush on top of the tube.
Isn't that strange?
I'm lucky enough in a way to have gotten a 2nd hand Domane with a long enough tube to play around before deciding what is a good height for me, but I'm also slightly worried about adding more than my current 10mm about the stem…
by MCBarista
3 Comments
There is nothing inherent in the concept of carbon steerers that requires a compression plug in order to counter-balance the compressive forces from a stem clamp. In fact, carbon tubes are able to take significant compressive force when it’s applied evenly. (The Titan submersible excepted.)
Rather, we’ve simply seen the specific requirements of some early designs turn into an almost religious dogma of How It Must Be Done, and lots of associated unfounded speculation and ritualistic behavior.
Trust Trek here. I don’t know if their recommendations are based on a different layup, different wall thicknesses, or just testing, and I don’t really care. Just take this as an example of where “rules of thumb” should be looked at cautiously in the modern (composite) age and we should be referencing primary sources more often than in years past.
I’ve always doubted the role of the compression plug.
But follow up question: Why does Trek specifies a maximum spacer height at all?
I have a mountain bike with carbon steer and 40mm stack below the stem. Just for my piece of mind I replaced the short stock compression plug with a 90mm long one instead that fills to the bottom of the headset spacers.
It’s probably overkill in my case, but might work for you until you find the stem height that works best for you.