Eunice:

The perfect driving line does change with the car. Imagine the difference between AWD/RWD/FWD.

Or compare the line of a car with less power/better handling to a car with more horsepower/less handling. 

Some of them would perform better on the longer and smoother outside route while others would be faster with a sharper bend and the shorter route.

That is obvious but difference is negligeable with respect to the overall length of the lap driven from start to finish, or have you ever heard of a RWD having an advantage over a FWD because it shortens the lap length for example?

What matters is the overall speed the line allows you to carry, that is why you do not approach a corner from the inside and exit on the inside just because its a shorter path around the corner than coming in from the outside, cut the late apex and exit towards the outside using as much or the road as posible (unless its chained to another corner and you have to sacrifice the exit of the first corner in order to have a better line on the second corner and have the best exit speed for the straight after it), the latter line is the perfect line because even though its a longer path, it allows you to carry a lot of speed, and while a RWD favors a slightly differnt line that may be by chance a cm shorter in some part of the corner it looses that cm in another part of the corner to the FWD.


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