Originally Posted by
cyccommute
The stem should be slightly above the steer tube. 3mm is about 1/8". If the steer tube is flush with the top of the stem, the top cap can't compress the bearings in the headset properly. You'll end up with a loose headset...not a good thing.
Not quite.
Something has to be above the steerer but it doesn't have to be the stem. A spacer will do fine as long as the top edge of the steerer is 2-3 mm below what ever is up there.
In fact, for carbon steerers, having the steerer project above the stem is desirable to assure the steerer fully supports the stem. Then a spacer above the stem is used to achieve the needed headset adjustment gap.