I remember playing Hard Drivin on the c64, it was a terrible port. The spectrum version was great though.
Spiritual successor? In terms of realistic car modeling, I would say the rFactor series.
In terms of modeling I'm sure you're right. Something about Hard Drivin' makes it feel not like a straight up racing game. It was an odd combination of physics + disembodied stunt tracks.
The combo of a sim, but a playful environment seems very hard to find.
I see your point, maybe something like BeamNG.drive when it is finished.
https://en.wikipedia.org/wiki/Hard_Drivin%27
I thought it was fun due to its realism.
also this bit is interesting from the wikipedia page
Physics The engine, transmission control, suspension, and tire physics were modeled in conjunction with Doug Milliken[18] who was listed as a test driver in the game credits. In the 1950s his father William Milliken of Milliken Research led a team at Cornell Aeronautical Laboratory in Buffalo NY USA (later Calspan) that converted aircraft equations of motion to equations of motion for the automobile, and became one of the world's leading experts in car modeling.
BTW, what is the spiritual successor to Hard Drivin' today?