Spaces on a threadless headset stem

Colin Blackburn said:

How exact do the spacers need to be when putting a stem on a threadless headset?

If I can't get a combination of spacers to be exact is it better to be wrong one way or the other?

There is no 'exact', the stem/top spacer must be sufficiently far above the steerer tube that the
cap will tighten properly, but the stem should be suficiently far onto the steerer that it clamps
properly (some/many stems have an indication of this depth). If the steerer is too long then you'll
not get the headset tight.

James

Colin Blackburn said:

How exact do the spacers need to be when putting a stem on a threadless headset?

Park say there should be "about a 3mm" gap between steerer and top of stem or spacer, and advise:
"The stem needs to press down on the spacers in order to adjust the bearings. If the steering column
is level with the top of the stem, another spacer is needed below the stem."

I reckon 2 to 4mm is ok (or a little bit more or less depending on stem and top cap design). If
can't get close enough with existing spacers, get some (more) 2 & 5mm spacers. Should be able to get
within 1mm with the right clever combination of spacers.

Quoted message said:

If I can't get a combination of spacers to be exact is it better to be wrong one way or the other?

Got to make sure top cap is not pressing directly on steerer, so I prefer to have too much of a gap
rather than too little, but don't go too far, else the top of the stem won't be clamping well.

~PB

Pete Biggs wrote: [...]

Quoted message said:

Got to make sure top cap is not pressing directly on steerer, so I prefer to have too much of a
gap rather than too little, but don't go too far, else the top of the stem won't be clamping well.

Thanks to both respondents. Now where did I put that little metal ring?

Colin