Car shudders while braking...
This can be caused by:
1) the braking system,
2) improper balanced wheels
3) damaged tires
The rotors are attached to the car with one alignment bolt. The rotor itself is in contact with the cars' axle by a cones shaped edge all around the center. If there is rust between this contact surface (not cleaned properly during the installation of the new rotors), it will cause some shuddering when braking.
The rotors can be warped (production fault or caused by water when hot). The caliper bolt(s) can be loose (a little).
The complete wheel can be damaged (not round) or just improper balanced. The tire can be damaged.
...just some thoughts...greetingz,
with a minor 600+k