Threadless Stem
 

I'm installing a threadless stem on an alloy steer tube. The steer tube was cut too short for the stem, so I need to place a 3mm spacer under the stem. This does not allow me use a spacer between the top of the stem and the cap. Is this an issue? I was told that one should have at least a 5mm spacer between the top of the stem and the cap. Does this rule only apply to carbon steer tubes?

Can I get away with no spacer between the top of the stem and the cap on an alloy steer tube?

I should mention, despite not having a spacer between the top of the stem and the cap, everything seems to tighten up just fine, and feels pretty solid.

Thanks.

You don't need a spacer above the stem , as long there 3mm between the stem and the tube for the cap to work . The cap is for adjusting the headset and once that done it lock in place by the stem anyway . as long the tube is long enough for both bolts on the stem to hold .

Metal steerers don't usually need a spacer above the stem. Carbon steerers often are required to do so. Andy

I don't get the question.

If the steerer is too short, adding a spacer top or bottom only makes it worse.

Back to the basics. The steerer must end below the top of the stem and spacer stack. This allows the top cap to push the stack down and compress the headset.

Ideally, the steerer should end 2-3 short of the top of the stack. Add or remove spacers to achieve that. The sequence doesn't matter, so whatever you prefer is OK.

Metal steerer, generally it is OK as long as the top bolt of the 2 in the stem is gripping it, and not above it's top edge..

Sometimes you can solve the problem of a too short steerer by using a stem with a lower stack height.