steering wandering on nnbs

[chartersj]

I have been trying to figure out why our 2011 yukon wanders all over the road and steering wheel shakes over bumps. I had it aligned this week and the dealership says everything is tight. I have 22" escalade rims on it, the tires are getting wore down, but i just tried the 22's on my 2011 silverado today and the truck does follow the low spots in the road, but the steering wheel does not shake over bumps at all with them. The yukon will pull be pulling left or right on flat roads, hit a small bump then dart the opposite way, and its very hard to keep driving straight down the road. The truck does none of that with them. I put the 20's off my truck on the yukon and it drives much better, i could feel a little bit of wobble over bumps in the steering wheel but nothing like with the 22's on. Something must be worn on the yukon to make it act that way, and was wondering if the front ends are the same between the two? Do the rack and pinions wear causing these symptoms or would it not have aligned properly if that was the case?