GM-GMC: 2007 GMC Brake shimmy, gmc 4x4, 20 rims and tires

Question
I have a 2007 GMC 4x4 with the 5.3l.  When i apply the brakes i get a shimmy that is pretty bad.  I have to be going over 50mph for this to happen.  I checked the rear shoe's and they are good.  The front pads have already been changed.  What else can this be.  I have put 20" rims and tires on it.  Not sure what else to check.

Answer
i had this happen to me but with my car. and i hope your truck is still in warranty? mine was because the factory rotors were garbage and had the brakes done 3 times before i finally replaced the OEM rotors with better aftermarket ones and upgraded the pads to ceramic ones. this finally fixed the issue.

i would call gm to see if there is any kind of issue with that since your truck is so new.