Caster off on one side

[ericsmith32]

Having problems with the Aspire... makes it real interesting to drive to say the least. They call it tramlining.. basically its one wandering fool. At first I thought it was the new tires I put on. But it has always existed with different tires just at different degrees of severity. I had a alignment done and they got to line up good, the caster on one side was flagged though. I've read that if caster is negative it will cause it. I don't think overall it was negative though. (Sorry don't have the paperwork on me).

My question is how can the caster be adjusted? Did I tighten the sway bar to much? The control arm I put on so I know its not bent.