There are (were) 3 versions of the car. TC5 (discontinued), TC5F, and TC5R. The F is the foam edition - stiffer chassis and top deck, different springs, etc. for running foam on carpet. The R is the rubber edition - more flexible chassis and top deck, etc. for running rubber tires.
The original TC5 was just kinda standard and in the middle, not really specialized for foam or rubber.
Glitter Lidz - "My driving doesn't shine but my lid does!!"