Originally Posted by
roadiejorge
This. I have a 5mm spacer between the cap and the stem and it makes sense because it doesn't seem like a good idea to have that much pressure close to the end of the steerer tube, especially carbon since it would crack if too much torque is applied.
This. The top bolt of the stem will have very little effect if the carbon steerer tube is flexing and cracks. A few mm down from the end of the tube it is much stronger.