The Rear Motor Mount is commonly known as the first modification owners should make to their car. Stock Fiesta STs have some serious issues with their rear motor mounts. Firstly, under heavy acceleration when shifting the engine can actually knock against theengine bay creating a rather audible bang. Secondly
, the stock mount allows the wheel to “hop” as you shift or start from a stop. This hopreduces traction and causes a shift in the weight of the car that could offset the car during a corner.
Aftermarket mounts negate these two effects by providing a tougher bushing that will not allow the engine to move as much. This can be met with some negative effects. Some rear motor mounts cause vibrations throughout the cabin and in some cases this can be unbearable. My recommendation lands with the Cobb rear motor mount as it adds the least amount of vibrations within the camera, many users claiming it is no different from stock other than the positives.