Vibration - Braking over 40mph

[jsm10]

All, I am hoping someone can help me with some advise.  My wife's 2011 Tahoe had a couple of issues.  The first is a noticeable vibration when braking at 40mph and above.  The other problem was a typical brake grabbing when you have a warped disk brake rotor.  I changed both back rotors and the issue with the brake grabbing went away.  The grabbing was what I consider typical warped rotor behavior.  You could feel it at nearly all speeds with varying frequency with the vehicle speed.  However, I am somewhat puzzled by the vibration during braking that only occurs at about 40mph+ that is still remaining.  Absolutely no issues at lower speeds.  I was thinking maybe it could be the front rotors, but I would think a warped rotor would cause problems at all speeds.  Before I threw money at a set of front rotors, I figured I would try to get some input from other folks.  Is there anything else that could cause this (cupped tires, slop in a ball joint, etc.) or is a set of front rotors probably the best place to start?  Thanks in advance! 

[riverbanks]

You got it, nothing like a second opinion though,change the fronts, make sure all pads slide freely, dragging causes warping

[jsm10]

Thanks!  Going to give the rotors a shot and see what happens.

[karlmg]

Aside from the brakes, check the steering components for tightness.