Thinking of a 8000kv Mamba MRS4

1/10 tires are way too huge and will stress out the driveline, they do make adapters for touring car wheels though and there's a few spikey tires availible for those.

Have you already bought the system yet? If not, just go with a slower motor, my 6800 in my 18t is almost too much for the small 200' long street next to my house, not just because of the speed either.....the truck has super acceleration too. Maybe just go with a 5400 system, then run more voltage if you want to go faster (i.e. 3s lipo or 12 cells). It will still be more than enough in the Micro RS4 and pretty quick in a 18t as well, 8000's are flat out stupidly powerful, and almost uncontrollable because they like to flip forward on hard braking and make steering inputs dicey at high speeds.