About 2 months ago I had a pair of Nitto 555's mounted and balanced on my front rims. I went with the 245/24 17 on the stock rims. After I left the shop I noticed a vibration in the steering wheel. I know the car has straight alignment but the steering wheel seems to shim back and forth from left to right. I took the car back in a couple days later and had the tires rebalanced. Of course it was due to a bad balance. But the last couple of weeks now it has been acting up again. If I let my hands off the steering wheel the car stays straight, but the steering wheel vibrates back and forth about an inch. Any ideas what this could be? I'm not sure if the tires are still not balanced properly or is there possibly some damper that can be adjusted to tighten up the feel of the steering wheel. Anybody have any suggestions?