OK, wanted to answer this post so it may be of help to someone.
I measured my 1968 Lemans steering wheel, the standard offered wheel, not the deluxe wood wheel. I am not a steering wheel expert and am not sure if the industry standard uses the outside measurement of the wheel, the inside steel ring to which the plastic outer rim is molded, or some other way. I for the most part am figuring on an outside diameter used to measure a wheel, but was also able to measure the core steel ring.
I measured using a tape measure (not the most accurate) and placing the tape on the outside of the molded plastic rim - so there could be variances in measurements from one wheel to another, but this should be close.
I measured horizontal (side-to-side) across at the spokes. I get 16" outside to outside. The metal trim on the spokes is even with the molded plastic rim, so no extra protrusion on the width measurement. I get 15 1/8" outside to outside measuring vertical ( top-to-bottom). So not a perfect circle and this was confirmed as I took diagonal measurements - wider at the center and narrowed down as you measured vertical.
My wheel is shot, really cracked and split, to the point I can see the steel inner ring which the plastic is molded on to. Measuring top-to-bottom from the center to center of the formed core steel ring, I get 14 1/2" (14.500").
My wheel is cracked enough that the steel rod is .370" in diameter as I measured it. At the top of my wheel (the vertical position), the edge of the plastic measured down into the edge of the steel rod was .130". Opposite this at the bottom vertical, I got .275," or just more than double at the top which would indicate a shift in the steel ring - ie, not a perfectly centered orientation between the steel ring core and the molded outer plastic ring. Taking the steel core ring measurement and adding the above numbers, 14.500" + .405" (.130"+.275") = 14.905" which is not far off from what I got with the 15 1/8" outside vertical measurement.
That said, in my opinion, the steering wheel is a 15" diameter wheel. However, if using just the vertical measurement only (which is the way most of us would quickly measure a steering wheel), someone would also be correct to call it a 16" wheel.
What you can say without question is that it is not
a 14" wheel.