Highway speed being 70 mph+ ?
That's where aerodynamics comes into play......
If your car sits level or a little "front high" (large tires may do that), the winds at that speed will tend to lift the front and lower tire contact with the road.
Suspension adjustments should correct that, and even tire sizing will play a part. I went with adding a front spoiler, and I've seen some improvement with that as well.
P.S., There are tons of OEM options available to accomplish what you're trying to do.