[Closed] Slamming stem on a carbon steerer - extra spacer on stem needed?

I wouldn’t have thought it makes blind bit of difference. So are Cannondale implying you can only run their bikes slammed no spacers at all 🤔

I run spacer on top of slammed stem only to give new buyer option to raise it when I sell it on.

I always run a 5mm one above the stem having once been advised to do so by an LBS. Can't imagine it makes much difference but it's not really noticeable and I suppose gives you the option to raise the stem a fraction if you ever need to.

The Cannondale Si top cap / bung system is designed to internally support the carbon steerer (on their ally steerer bike it has usual star nut flat top cap setup).

On their carbon steerers the top cap fits inside the steerer for the top of the stem, the bung is to be fitted a set distance inside to align with bottom of stem.

For bike brands where a spacer must be fitted on top of the stem it is as they are designed for the steerer to finish above the top of the stem - spacer is then needed of course.

Yes it's about supporting the steerer from crushing forces of the stem

Some also say you need a spacer below the stem (Scott I think). Some say carbon paste on the steerer a must, other's say never use it (Trek?).

It's the boring answer but I'd do what your particular manufacturer says in case you get a warranty issue later.

Good excuse though, "It's not my middle aged lack of flexibility, they've made me put a spacer below the stem...."