Bumpy ride.

My 95 Chevy Lumina has a 3.1 engine, automatic transmission, and about 179,000 miles. Over the past few months, I notice at slow speeds that the car often rides bumpy. I recently had the goodyear tires rotated and balanced. I have been doing that every 3 months for the past year. At the most recent rotation, the dealer said that a rim was bent and that it may have been causing the bumpy feeling. I replaced the rim that same day through the dealer. They said that there were no broken belts in the tires. Unfortunately I still have that nagging bumpiness at slow speeds. The car rides smoothly at the speed limit and is in good alignment. Any ideas? Thanks