The subframe is part of the vehicle chassis and, despite its size, is relatively straightforward to refit. A car can fail its MOT if the subframe is corroded, so it must be routinely checked for unwanted moisture and general rust. Given that the subframe holds most of what sits in the front of a vehicle, its size can sometimes lead to loosening bolts that cause rattling and shaking in the engine bay. If you experience this, consult a mechanic to find the right fitting for you.