I agree with DaredevilD about foam tires not lasting. I wounder why US people run foam tires when they could run rubber. Most all indoor carpet tracks on the east coast runs foam tires. Sure they are a tick faster but you have to deal with ride height, roll out, tire wear, over/under doping and chunking. Rubber tires are less hassle. With the right shore rating and temp. Tires in stock class should last twice as long (on carpet).
I just started running a 21.5 class with a HPI spec rubber tire. It is great to not deal with all the above. The car handles great with rubber. In fact more realistic then a foam tire.