A lexus problem

I was driving my wifes 2005 Lexus 330 on an Interstste between 65-70 mph. Suddenly the steering wheel started to vibrate as if I had a flat tire. I pulled over, checked-no flat. Cautiously started slowly then picked up speed til I was at 65 again. No problem. Drove all the way home (150 mi) next day, no problem. About 3 weeks later, the same thing happened to my wife on an interstate. Sje stopped, checked, no flat. Started up cautiously, then faster. A ll OK. Came home-no repeat of the problem. Took it to our dealer. Up it went on the lift. Diagnosis: 2 tires had steel belts that were out of shape and the car needed a slight alignment. $800+ bucks. A week later, on an interstate, she had a repeat of the problem. Lexus took the car and the service guys took turns drvng it home at interstate speeds. Couldn’t get a repeat of the problem. I don’t know if this would have any bearing on the situation, but the only thing we’ve done out of the ordinary is use regular gas about 3 of every 4 fill-ups (Chi prices are about $4.50 for regular). Will appreciate any insights. Thanks

What you’re feeling might be tire hop. Tire hop occurs when a front strut becomes worn out where it no longer dampens the spring oscillation. The spinning tire and the spring then reach a certain frequency where the tire starts hopping up and down rapidly off the pavement making it feel like there’s a flat tire. Sometimes just hitting a slight bump with the tire can set off the tire hop.

Unfortunately, the only way to find out if it’s a bad strut is to take the strut assembly apart.