pocono

I have a 2008 Highlander Limited. Paid a lot of $ for this baby. I have 5 - 19 inch wheels that are corroded. My Toyota dealer said it's because of what they put on our roads here in the Poconos of Northeast PA. Bull! I thought Alloy wheels resisted corrosion, I am not getting any cooperation from Toyota on this matter. I see there have been some other corrosion issues out there. Please let me know how to proceed or what to do?