Question about the 105mm accessory bar

[danfoto]

I've just fitted one to my Sherpa and I'm perplexed.

The spacers on my stem are either 6mm or 12mm high.  The collar by which the accessory bar attaches to the stem is 32mm high. 

I've had to take 30mm of spacers off my stem, which means that the top surface of the top-most spacer on the reassembled stem is now 2mm above the top of the steerer tube (? not sure that's the right term, but I mean the tube that's attached to the fork crown). This in turn means that the cap through which the headset adjustment bolt passes does not, for some reason, want to seat concentric with the top spacer.  And as an ex toolmaker I'm inclined to take that as a sign that something's not quite right.

So two questions really.  One is have I got it right with the spacers or am I missing something obvious?  And why oh why is the collar of the accessory bar not the logical height of 36mm?

 

[julk]

2mm of spacer above the top of the steerer tube sounds about right.
You want the top spacer to be a bit above the steerer to allow for adjustment of the headset bearings.

Why the top cap is not a good fit is a mystery to me - any possibility of a photo?

[danfoto]

2mm of spacer above the top of the steerer tube sounds about right.
You want the top spacer to be a bit above the steerer to allow for adjustment of the headset bearings.

OK, that makes sense so thank you.   Looks like the top spacer was originally only marginally above the steerer then.

I still think that collar should be a multiple of 6mm high though, and not 32mm

ETA - by the way, what kind of bearings are they?

[julk]

I bought and used a combination of smaller spacers to get the everything in place and the steerer just down inside the top spacer.
If you do that and you change your mind (I have) you can alter the setup to almost any combination of fittings and/or spacers.

The bearings are either all ball or roller or a race of each. I am sorry I have never dismantled my headset to find out, but would expect to find ball bearings.