i just got some tires put on and i get the 42-48mph bounce in the rear end as well. i'm going back to the shop that put them on and i'm gonna tell them that the balance didn't take and hopefully they won't charge me to re-balance them.

 

Yeah mine is real noticable at low 40-45, and later after OD kicks in at some point (i forget maybe 55-60). I find it hard to believe all of us have unbalanced tires causing the same exact problem. I watched the shop balance my tires right in front of my eyes so I know it was done correctly.

 

After I had mine balanced and rotated I'm pretty sure that the vibration got worse. I no longer get the pulse in braking, but this vibration is bouncing me to death.