Finally, other people have noted the problem with the peeling chrome on rims. Mine started on my 2000 GS300 when it was just out of warranty in 2002. The district rep for Lexus claimed they did not have a problem, but a few tire stores told me it was a common problem and blamed faulty chroming. I suspect it may also have to do with the way the tire install/removal equipment rubs on the rim as it does its job.
Nothing you can do except fill your tires every 3-4 days or buy non-lexus rims.
I am disappointed by lexus when it comes to taking responsibility for these type problems. Due to this and another problem, I have unfortunately put them in the "just like the rest of the A$%hole car companies" group.