After driving at 79 mps for about 5 or 6 hours the Dynamic Drive Failure (DDF)fault pops up. Then in about 20 minutes the tire fault pops up. We exit, turnoff the car, and check the tire pressure to be sure that they are all filled to 38 PSI, reset the tire monitor and drive off. The DDF has gone away, I thought. Then about 30 minutes later the DDF pops up again. After stopping and only taking short trips I have not seen the DDF pop up.
1) What are the problems with driving on the interstate with a DDF?
2) Is there an easy fix to the DDF problem.
3) What is the best PSI for my Bridgestone RFs when driving on the interstate at 70 to 80 MPH?

Thanks to all.