guys . . .
from the pics the cars are clearly sinking into the track . . .
now . . . on the track . . .
provided all the object names and materials are set up properly it could be the way the track model is set up . . .
i was asked recently to fix a track with a similar issue . . .
turned out the grass plane extended under the track sections and caused the cars to sink . . .
so in other words if this is the case the removal of any polys under the track will sort it . . .
if i get time will have a look to confirm . . .