My steering wheel shakes while I'm braking.
Brake pads are new
Rotors resurfaced and tires balanced.
What's causing it shake like that?

 

The Ujoint on the steering shaft could be worn out, the rack bushings could be worn out, the tires themselves could be out of round and you could have bad tie rods or steering rack.

Also make sure you use a torque wrench and properly tighten all the lugs to spec

 

Your tension rods. Check them for leakage