The front tires are Hoosier asphalt tires- I'm not sure if they are regular production or if they were custom-made for the Tumbler.
Ah, so there's an asphalt Modfied kit in Moebuis' future?! You read it hear first!!!
The front tires on the Tumbler toys I've seen all are peaked at the centerline, so they don't look very good, but those on the real Tumbler, and probably the Moebius kit, could be put to use by many people I'm sure.