Required spacer above stem - Trek Domane
 

In August I purchased a 2020 Trek Domane SL6.

When I brought it home, I noticed a 3mm spacer above the stem and the stem was angled down (-7 degrees). I wanted to flip the stem wanting a higher handlebar (neck issue), and to add a bit more, I wanted to place that 3mm spacer below the stem for a little extra height. I emailed the owner of the bike shop asking why the spacer was above the stem and if it would be ok to put this spacer under the stem. He said yes, no problem and "I think the tech just set it up the way they like it,..." I do understand I can buy a shorter stem with more rise, but I'm merely starting with this one (100mm at 7 degrees) to see how I feel.

A few weeks later I brought the bike in for an unrelated issue and when I got the bike back, the mechanic (not owner) stated that the 3mm spacer MUST to be above the stem. Something about the ISO speed coupler in the front fork.

Not that I don't trust him, but I wanted to see what the Domane Service Manual stated about it and how the ISO speed coupler is affected It's not in that service manual that I can find. But notice the photo on the Table of Contents page.....there's a spacer above the stem.
http://trek.scene7.com/is/content/Tr...ual_USEN_3.pdf

I'm wondering if other Domane owners have that same spacer above the stem? If yes, were you told why? If the spacer isn't there, should it be?

If the fork has a carbon steerer, then yes you need a spacer above stem. Additionally make sure the compression plug is centered in the stem to support the clamping force.

I see, well thank you, I did not know that. Yes, the Domane does have a carbon steerer. My Cervelo RS has a carbon steerer but no spacer above the stem, was never installed with one and is from the same bike shop.

The industry learns about stuff after bad things happen enough, like steerer tops cracking under the compression the stem's pinch bolts being too close to the steerer end. Some companies/shops/mechanics are more proactive about this type of thing then others are. Andy

Nothing to do with Isospeed coupler. If the steerer is carbon, put a spacer on top unless the manufacturer says otherwise (which I doubt).

Otherwise, your steerer may crack, and you don't want that to happen.