got the 5100's in front, alignment done and then rotated the tires side to side. all of a sudden i get a slight 1/4-1/2" wobble in the steering wheel around 55 mph. just enough to notice. if i let go of the wheel the truck tracks straight. above or below 55 and it is smooth.

i'm hoping it's a balance issue but thought i'd ask here before i start throwing $ around.

Sounds like an unbalanced wheel to me...

good to know. thanks!

I concur. I had that happen before, it only showed from 55-60, anything higher or lower and it was smooth.