STM Italy Street Wet Slipper Clutch Aprilia RSV4/Tuono V4 2009-Current
- Street Wet Slipper Clutch- Hub, Drum, Primary and Secondary Springs, associated parts and mounting hardware
- 121 mm primary spring * Also available in differant weights 90 kg to 190 kg
- 85 mm secondary spring * Also available in differant weights 30 kg to 80 kg
- Kit includes assembly instructions with disc pack diagram
- Each Street Wet Slipper Clutch come with suggested spring weights
- Ready to install as direct OEM replacement
Street Wet Slipper Clutch Details:
- The STM Wet Slipper Clutch is adjustable, by replacing primary and secondary springs the engine brake and clutch slip settings can be altered
- Built from hard steel alloy, the STM Wet Slipper Clutch is durable and doesn't wear as fast as other slipper clutch designs.
- Uses OEM friction plates, drive plates, and basket
- Engine oil lubricates and cools clutch plates, STM FLS (Forced Lubrication System) is designed to route oil through specifically designed passageways
- Cooler clutch temperatures increase performance and exend the life of the clutch
- The STM wet clutch a has larger friction zone which makes street riding easier.
- Direct replacement of the OEM clutch
- RSV4 2009- Current
- Tuono V4 2009- Current
Characteristics of STM EVO Slipper Clutches
There are 6 major components to a STM EVO Slipper Clutch: Hub, Drum, Pusher Plate, Spring Pusher and the Primary and Secondary Springs. Ball and ramp design allow the movement between the hub and inner drum > Secondary springs regulate amount of resistance to engine brake > Primary spring, pusher plate, spring pusher > Engage/disengage the clutch with the crankshaft input. The Ball and Ramp design allows the "slip" in the Slipper Clutch- reducing or eliminating wheel drag/rear wheel hop on down shift.
What is unique about the STM EVO slipper clutch?
Unlike other conventional coil spring slipper clutches the STM EVO clutch instead uses a preloaded primary and secondary diaphragm spring.
The Primary spring puts uniform pressure on the pusher plate and the clutch pack- acting as coil springs would. Primary springs are available in differant weights to match the characteristics (power) of the motorcycle engine. STM EVO clutch primary springs give consistant lever feel regardless of the wear condition of the clutch discs and a predictable, soft lever feel (if desired) compared to a conventional 6 helicoil spring setup.
The secondary spring controls the amount of pressure on the clutch drum and regulates the opening of the slipper clutch and amount of engine brake. Secondary spring.
- The STM EVO slipper clutch is adjustable, wherein the rider can adjust the amount of slip and engine braking- setting how much or how little the clutch slips is done by changing the weight of the secondary spring
- The lighter the secondary spring, the less engine brake there is.
- The heavier the secondary spring, the more engine brake there is.
- If a rider would like the feel of a 2-stroke engine for instance, then the lightest secondary spring possible would be used.
- The STM EVO slipper clutch primary and secondary springs have less drag than helicoil springs. This Diaphragm type spring is not under tension while the clutch is closed, unlike helicoil springs which are always slightly compressed.
- The STM EVO slipper clutch hub and drum are constructed of Steel Alloy- designed to be friction free with high wear resistance.
How a Slipper Clutch works:
~Without a slipper clutch
At speed- and on a sudden downshift and throttle closure, the motorcycles rear wheel abruptly slows, hopping or skidding as it meets back torque transmitted from the crankshaft. The rear wheel now wants to spin the engine, vice the engine spinning the rear wheel. This is caused by the engine revs suddenly increasing- due to a shorter gear being suddenly mismatched with the engine speed. This generates reverse torque (engine breaking)-putting energy from the crankshaft back into the clutch. With large displacement 4 stroke motors, more engine braking is generated- a 2-cyclinder Ducati 1198 as an example, can create a great deal of engine braking.
~With a slipper clutch
The reverse torque energy from the crankshaft is absorbed by the inner hub of the slipper clutch it's connected to- Similar to a torque wrench, a slipper clutch will break at a specific level of force- that force resistance is broke by the hub lifting up and shifting on the balls and ramps of clutch drum-pushing the clutch pressure plate out. This disengages the clutch friction discs, ultimately freeing the rear wheel from the torque of the engine.
On the racetrack it allows you a safer and more efficient way to enter a corner while downshifting on the brakes all the way to the apex. Not having to worry about locking up the rear wheel in the brake zone is a major reason why riders choose a slipper clutch for the race track. With motorcycles that do not have electronic engine braking rider assistance, an STM EVO slipper clutch can also provide a level of tunability that cannot be acheived otherwise.
Benefits of the Slipper Clutch:
- Prevent engine overrev
- Reduced clutch lever pressure
- Better grip in the clutch pack on acceleration
- Assists the rear shock and chassis to remain stable on corner entry
- Prevents rear wheel lockup before and during corner entry, emergency braking/down shifting
- Can downshift without using the clutch lever (your clutch will last longer if you don't do this)
- Enable the controlled sliding of your rear wheel (backing it in)
- Better clutch lever release from a stop light or starting grid- due to the diaphragm spring
- Preventing damage to your engine components and gearbox
- Mechanically assists and simulates feathering clutch manually- like required when riding without a Slipper Clutch
- Can enable faster lap time on the race track- enabling quicker down shifts and less to worry about in the brake zone.