i've tried a couple of cars and all work fine , though I have had the NewtonVehicleAddTyre crash before too , usually it ends up the car and tires not being groupped up properly , or a tire not having it's action set , or that i didnt recompile the level , so try those things , check that every tire has the tire action , that the car model has it's proper action , that they're groupped correctly , and compile the level , close gamestudio , reopen it , and run the level , should work . For some reason sometimes if you dont restart gamestudio after recompiling after the tyre error u'll keep on getting it untill u restart the proggie.