Alighnment

It's much more common for the trailers to have issues that cause it to dog-leg than the tractor. Your tractor's drive tires would show signs of wear if the tractor was far enough out of alignment to cause a trailer to dog-leg. Also, if your trailer alignment was causing the issue every trailer you pull would dog-leg or ride left/right of the tractor when going down the road.

 

Trailer's track from the kingpin to the axles.

You check the trailer alignment measuring from a plumb bob hanging from the kingpin to the axle ends so repeated curb strikes can slowly change the alignment which kicks the trailer doggy.

That's why most run doggy to the shoulder as that side is most common to strike the curbs.

Tractor alignment should include all three axles; had a fleet truck where the driver constantly gripped about fighting the wheel most of the time while driving down the interstate.

After it scrubbed off the original steers in the first 80K miles we sent it to a shop specializing in a 3 axle alignment and it returned with new torque arms on the drives with a warranty.

Driver couldn't believe the difference as he had been on his former bosses since the truck was delivered and it was the first thing thrown at me when I took over as manager.