1991 Lexus LS 400 Tires and Shocks

This is an older car but has been very well maintained. The model comes with a ride height adjustment feature for normal height or high ride height for poor road conditions. I noticed tire noise and had it put up on lifts to see what was happening. The rear tires are feathering and I am pretty sure that the back shocks are shot but the front tires are cupping. The front suspension is an air shock and was on normal height. If the rear shocks are bad will the ride height adjustment cause a problem with the tires in the front? The height adjustment seems to work.