I just put a 4" suspension lift on my 96 f150. Everything went pretty smooth. I took it to my local mechanic to get aligned with my stock tires on and it drove great. Then I bought a brand new set of mounted and balanced Mickey Thompson 33" 12.5 baja claws mounted on M/T 15" x 10" classic lock rims. Put them on and was loving it, it looked great. Then I drove it. My truck pulls severly to the left!!! I can see nothing wrong. Tire pressure is fine. What could possibly be making my truck do this????

 

Makes me wonder if everything was good and tight after the alignment.

Did you take it offroad after putting on the new tires?

 

Could be the tires. I have had problems with tires before that would cause it to pull either right or left. Swap sides with the tire and see if it pulls to ther other side.