Combustion engines have a problem: They provide a usable output only in a very specific speed range – just the opposite to electric or steam engines. This means that speed, transferable engine output and gearbox must be optimally synchronised in various drive conditions – this function is provided by the clutch. The clutch separates or connects powertrain from and to the gearbox, which every driver knows from his own experience. When the clutch pedal is depressed, this powertrain is interrupted and a different gear can be engaged. The clutch also enables cars, trucks and other utility vehicles to accelerate away smoothly and without engine bucking.