Some cities or counties have annual or semi-annual white goods (fridges and air conditioners) recycling, and they will include used tires.

Call your county office and they'll direct you.

Where I'm originally from, LaPorte, Indiana (up north for all you southerners), the county has twice a year white goods/tire drop off at the county fairgrounds. Now and again they include paints and out of date or no longer used medicines (dropping medicines/scripts down the toilet pollutes the water).

Google tire recycling in your county and you might be able to get rid of them free.