We were taxed at the Otay border yesterday for every spare tire over 6. They tried to say only 4 were allowed, but we had the border crossing letter from SCORE which stated 6. They then placed a value on the tires at $300 each, and taxed us at 16%. Also, make sure you have your original paperwork on your vehicles. They would not take copies this time. Just an FYI for people coming down.