Pete, Good work. I checked the geometry and got 326.4516m A 2.4 mm disagreement is not worth investigating and wont affect your overall result.
So I predict your concrete is indeed a lot smoother than your asphalt. Can you post macro digital photos of both surfaces?
Better still try a trick that a road engineer once described to me. Take a measured volume of fine dry sand and brush it into the surface so it just covers a patch. Roughly estimate the area of the patch. Repeat on the other surface. Compare the areas. The larger the patch the smoother the surface. I have never actually followed this advice, and I can see somethings wrong with it.
For the measurement of the Sydney Olympic course I got Hugh Jones to make castings of the surface and send them to me for inspection, and correlation with the results from the different measuring tyres used. There was some qualitative explanation of which riders got which distances, but overall there was too much going on to make much of it, and I never wrote it up.
By a coincidence Hugh has just left two days ago to measure Bejing with Dave Cundy. I did not suggest the experiment again. He has got more important things to do than feed my curiosity!