Double-clutching is a driving technique solely used in manual transmission vehicles. To understand how it works, the most important thing to know is that there are three systems involved: the engine, the clutch, and the transmission. Your engine produces power, the clutch transmits that power to the transmission, and the transmission sends the power to driven wheels. Each one of these systems, the engine output shaft, the clutch, and the transmission output shaft, can all rotate independently.
The purpose of a clutch is to act as a buffer between the engine and transmission, so when the speeds are mismatched, the clutch is utilized to sync the two systems together. The rotation speed of the transmission output shaft, the shaft that’s sending power to driven wheels, however, is dependent on what gear the transmission is in. In lower gears, the engine will spin fast relative to the transmission output shaft. In high gears, the transmission output shaft will spin quickly relative to the engine.
Double clutching, although (slightly) time consuming, eases gear selection when an extended delay or variance exists between engine and transmission speeds, and delays the wearing on the synchronizers, which are just brass cone clutches themselves, and wear out slightly a little bit every time they are used to equalize the transmission revs with the output revs.
One can “rev match” the same way without declutching the first time to take the transmission out of gear; as long as it’s not under load, a transmission can usually be pulled out of gear and into neutral without significant difficulty, and then the operator can match revs, clutch and engage gear in the same manner as previously described. The first declutching is simply to make taking the transmission out of gear easier. It is also possible to rev match and shift into a lower gear without using the clutch at all, but unless one is very skilled and practiced, this will generally take a lot of material off the synchros or grind quite a bit until it gets into gear (with unsynchronized transmissions). Provided one correctly matches the revs, a transmission can be shifted into gear quite easily without any clutch, but this is usually best left for emergencies only for the average automobile driver.
While most prior vehicles needed to be double-clutched to ease gear selection, there is no need to add the extra wear-and-tear to your current clutch system. For any type of clutch repair and replacement contact us today.
Cover Image Credit: Mazda Parts