For manual transmission vehicles, the stroke of the clutch diaphragm spring, which is for pressing the clutch disc onto the flywheel, is not properly set, and therefore, excessive load may be put on the clutch diaphragm spring, when the clutch pedal is depressed to the maximum in a cold ambient temperature. If this problem is left unattended, the clutch diaphragm spring may break, in which case, the clutch could remain connected and the gear change could become impossible.