I'm currently working on an official model which requires part 61254, listed as "TYRE LOW NARROW Ø24x7MM" in LEGO's database. It doesn't appear to be in either the most recent AIOI, complete.zip, or the parts tracker, but the most recent ldraw.xml makes reference to a "Tyre Small New" as 61254.dat. Does this part actually exist? If not, I would like to request it. This part does exist within LDD.
Would an export of the geometry from LDD help?
Yeah, it probably would.
The part looks quite familiar to me though, I wonder if I actually have one of these floating somewhere around.. though that'd qualify as an archeological discovery when it comes to my way of sorting non-Technic bricks. :p
It looks very similar to the previous Tyre Small, I think. If the LDD geometry is accurate, I would guess that the treading is very slightly different and that the outer diameter is a tiny bit smaller. I'm attaching the LDD geometry. I'm not really sure what would be required to make this a suitable LDraw part.
Working on it, based on LDD...