CLUTCH PROGRESSIVITY

The clutch progressivity is a characteristic that determines how smoothly, evenly and predictably the driver can control the connection of the engine to the wheels, i.e. control the transmission of torque from the engine to the transmission when releasing the clutch pedal.

Proper progressivity ensures a comfortable start without jerks, smooth gear shifting, reduced wear on transmission parts, and improved vehicle handling.

On modern cars, the progressive activation is determined by the design of the clutch and its drive, as well as the lining material of the driven disc.

Types of clutch actuation characteristics:

• Linear progressivity. The torque increases in proportion to the time or stroke of the clutch pedal.
• Nonlinear progressivity. The transmitted moment grows according to a more complex relationship: at first smoothly, then faster. 
• Smooth progressivity is optimal for comfort. It is typical for most modern cars, where soft work is important, the absence of jerks at low revs.

The main aspects of progressivity are the

• smoothness of the increase in force when the clutch is engaged
• uniformity of torque transfer from the engine to the transmission
• pedal sensitivity to driver's efforts

The clutch progressivity is influenced by a combination of engineering and design solutions.

Pressure plate design:

• diaphragm spring – this type is used in modern cars. At the beginning of the pedal stroke, the force increases smoothly, which allows you to precisely dose the moment, and closer to full power — more sharply, ensuring reliable clamping and no slippage.
• cylindrical springs are an obsolete type. They often have a more linear or even sharp characteristic, which makes the activation less predictable and more "jerky".

Characteristics of the slave disk:

• damping springs – these springs located inside the hub of the disc are designed to dampen torsional vibrations and shock loads. Their rigidity and quantity directly affect the softness and smoothness of picking up the moment.
• friction material – the composition and wear resistance of the pads also affect the nature of the grip on the flywheel.