We always did the old tires as plant some add a tire layer them then you canOne mistake I made I didn't put a bottom in I got hit with gophers and voles/mice I will put 1/2" hardware cloth on the bottom this year. The garden did so well they didn't hurt me to bad but it ticked me off. I also had about 20 grow bags I grew potatoes in they did really well and easy to harvest just dump them out.
take them off as you harvest also