This doesn't make much sense. The surface you run on is about the same as ours here. Isn't ashphalt ashphalt?
Do you guys use anything to treat the surface of the track?
Sugar? VHT? Soda+ Castor+ Alcohol?
Is it Sealcoated? If you sealcoat your track, tire wear with foam goes way way down. On sealcoated tracks (there are 2 that I go to) foam is pretty much the ONLY thing that works. Perhaps thats why we run foam only. On ashphault which is very abrasive, perhaps rubber compounds will last longer than foams.
When we use VHT, by the time a lot of cars run on the track, tire wear goes down, and Traction is always good.
On tracks with just ashphalt, no treatment, it takes a lot of cars running foam to wear into the surface before traction goes up and tire wear is down. If it rains, then start all over again. This was the case at the 1/8th worlds in Cincinnati which I did get to see (No, I didn't get any pics of the Venuzualian, but she did stand right next to me for while).