While you're at it, try this:
flip the bike upside down, and point the front wheel straight forward. Judge by the wheel/frame, not the bar. Now hunker down a couple of yards/meters away from the bike and look along the wheels. Do they track as they should?
On a healthy bike the wheels should align "perfectly", and have the rims in the same plane.(that is, if you ran one piece of string between the top part of the wheels and another between the bottom parts of the wheels both pieces of string should come out parallell.) If they don't, something is wrong.