Many things can cause a car to shake. The main reasons are; tyre imbalance; uneven wear; tyre separation; an out of round or bulging tyre; flat spotting; and warped break rotors. In most cases you will start to feel a shake as the car reaches between 50-100km/h. If you feel shaking through the steering wheel, it is generally the front wheels, while if you feel shaking through the body or base of the driver’s seat, it is in the rear. If you find you only get a shake or shudder under breaking, it is generally caused by the warped front brake rotors.