No matter how much power the engine makes, if just one of the clutch components isn’t working as it should, you won’t be going anywhere. This is the missing link between rumbling pistons, conrods and cranks, and the wheels. It’s what makes the transfer of power possible, so a good clutch will make the best use of what an engine has to give.
What are Clutches?
Clutches are the mechanical components tasked with the transmission of power from one vehicle part to another. They take engine power and connect it to the drive shaft and then onto the driven wheels. The same component allows drivers to disengage the engine power (by pressing the clutch pedal) while changing gears. And while there are different types of clutches, you’ll need the right one for your vehicle and engine, to maximise the transfer of rotating force or torque through the gearing and down to the wheels.
Types of Clutches and How They Work
Clutches come in a few varieties, The working principle is similar, but a few additional components make the best use of power in different types of engines. The most common clutch for cars is the friction clutch, This consists of a release bearing, a pressure plate, and a clutch plate and operates either by a mechanical cable or with hydraulics. The bearing is the component that engages or disengages the flywheel and the transmission.
Single-plate friction clutches are by far the most common in the majority of cars, while high-powered vehicles may use a multi-plate clutch. The functioning of the whole assembly is relatively simple. When drivers press on the clutch pedal, the flywheel and transmission are disconnected, or more precisely, the bearings apply pressure to the springs in the pressure plate and this releases the clutch plate.
Multiplate clutches use several friction plates stacked together and this is what you’ll find in cars with high torque output. The assembly is both efficient while at the same time preventing damage to separate parts. Single-plate and multi-plate clutches can further be classified into dry and wet clutches. The latter use oil for lubrication and cooling of the components, and are mostly found in multi-plate car and motorbike clutches with very high power output numbers.
Dual clutch systems are a recent addition, providing smooth and fast shifting between gears. They do this by utilising a separate clutch for even gears, and a larger clutch for the odd gears, meaning at any given time one of the clutches will always be engaged. This helps with power transfer and can substantially reduce fuel use. Lastly, electromagnet clutches are found where the is no need for a clutch pedal, instead, the clutch assembly is engaged and disengaged by a pair of paddle shifters located on or near the steering column.
Materials
The materials used in different clutch parts determine how long they last and how efficiently power is transferred from the engine to the transmission. There’s a divide between what is used in everyday passenger car applications and what you’ll find in vehicles deemed for the track. Outer pressure plates are most often a sprung-metal design, while there’s more variety in the friction plates. These can be made of organic materials, and are adequate for most day-to-day driving as they allow for smooth and quiet operation. However, they do suffer under heavier loads, and this affects durability. Friction plates made of carbon or Kevlar composites handle high heat much better, so are more in line with the torque that comes out of high-performance engines.
Lastly, the best clamping force (and the least ‘clutch slip’) is offered with a ceramic friction plate, though connecting parts like flywheels also need to be made tough. This is what you’ll find in purebred race vehicles.
If you’re upgrading the clutch for your car, then materials will have a major impact on price, but also provide the needed boost in smooth power transfer. An aftermarket clutch for cars will be paired with a significantly lighter flywheel as this puts a lower burden on the engine, with less mass to turn and gets the revs up quicker. Shifting will also be lighter and there’ll be less power lost.
Common Signs of Clutch Failure
Clutches can last up to 200 thousand kilometres, but some do call it quits much earlier. A determining factor here is how hard you’re on the engine and gearing. Problems can occur gradually or come on at once and often without prior warning.
Clutch slip is one of the most frequent issues with worn-out clutch components and this happens when the car is in gear but can’t transfer power to the wheels. The loss of power and poor acceleration can also be accompanied by the engine holding on to unusually high RPMs. Drivers may also find it hard to change gears, and the clutch pedal acting up. Stiff clutch feel results from damage to mechanical cables, loss of hydraulic fluid, or worn-out pressure plates. And a soft clutch will have a lower catch point than usual and can be coupled with burning smells and grinding noises as parts start to overheat.
These and similar issues should be dealt with promptly as they can pose a serious safety hazard. OEM replacement and uprated car clutch kits are sold online and in-store at all major automotive retailers.