How do I replace the rear tires on my riding mower?

I have a riding mower purchased from Lowe's just over 10 years ago and all tires need to be replaced. It has a 12.5 Briggs & Stratton engine with a 42" cutting deck. It also has a MTD sticker under the seat when lifted forward. I was able to remove the front tires and rims just fine. Now the task seems to be getting the rear ones off. I removed the center bolt and washer on each but they won't budge. Is there something else that needs to be loosened or do i just need to pound them off with a hammer? I want to take all four in and have new Carlisle Turf Mate's put on. Help?