I put the snow tires on a few weeks ago. I know, I know, winter's almost over. What took so long? Well, I put them on (mounted on seperate steel wheels) on Wednesday for a Friday trip. Friday afternoon rolls around, and the passenger side tire is flat. Not leaking, not low, FLAT. I filled it up and waited three hours (length of the impending trip). It leaked from 36psi to 32, so I felt safe. Got where I was going fine. I had to drive back Sunday, and didn't have an air compressor handy to fill the tire. So I bought a can of fix-a-flat, used it, drove a few miles to distribute the stuff, and drove home.

After that build-up, here's the issue. On the drive home, I noticed an odd vibration that wasn't there before. It wasn't all that pronounced in the body of the car, but it could definitely be felt going side to side in the steering. What was odd about it was that it was sporadic. It would shake back and forth 3 or 4 times, then stop. The period was about a second, going 1-2-3 rest. The shakes taking about a half second, and the rest taking another half second. It really didn't vary by speed.

Any thoughts on what it could be? Could it just be an imbalance from the fix-a-flat? or could it be ball joint/tie rod related? Any diagnostic tips?