Finally got my tires mounted on the RPF1's and noticed this black o-ring on the inside of the wheel, right where the axle nut goes through. I think it is referred to as a spacer. Do I keep it, or remove it?

 

That's called a "hubcentric ring". Its purpose is to reduce the diameter of the center bore (that's the big hole in the center of the wheel) so that it just fits over the hub (the part that surrounds the end of the axle nut) without any gap. Without a hubcentric ring, the center bore would be much bigger than the hub, which leaves the job of centering the wheel solely to the lug nuts, and makes the wheel more susceptible to vibrations from being ever so slightly off center.

As long as the hubcentric ring sits just over/around the hub, leave it in and use it.

Also, I'm curious about something. From the photo, it looks sort of like the seating area of the wheels - the part that comes into contact with the lug nuts - is ball-shaped (radius), rather than tapered (cone). Is that correct, or is that just an illusion in the photo? Most aftermarket wheels have a conical/tapered shaped seating area, whereas Honda/Acura wheels use a ball-shaped seating area, so this would be rather unusual. (You should be using lug nuts which have the same shape seating area as the wheels.) See the photo below to help understand what I'm talking about.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">

Also, I'm curious about something. From the photo, it looks sort of like the seating area of the wheels - the part that comes into contact with the lug nuts - is ball-shaped (radius), rather than tapered (cone). Is that correct, or is that just an illusion in the photo?
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not exactly sure. Let me go take some more pics of the wheels and lugnuts.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gursh d &raquo;</TD></TR><TR><TD CLASS="quote">not exactly sure. Let me go take some more pics of the wheels and lugnuts. </TD></TR></TABLE>

I find that it's easiest to tell by running your fingertips over the seating area. You should be able to tell whether it's conical or ball-shaped that way.

 

its a cone shape.