Thanks for responding. I do keep my car aligned, have the tire pressure checked regularly and am well known for my slow driving. (My kids wear dark glasses when riding with me because I am the one in the right lane driving the speed limit.) The psi idea is not one I have tried. My mechanic, who has worked on all 4 of our Toyotas for years, said he sees this problem with the Sienna and the Solara. He thinks it is a design problem. I wonder if a change from Bridgestone or Dunlap will help. Both have been subject to recalls previously to to quality issues on the Siennas. The dealership is recommending Yokahama. Any thoughts? Thanks again. I appreciate the ideas.