While STM has been making dry-clutch slipper applications for Ducatis since the 1990s, the company's wet-clutch slippers date back to 2002 with Aprilia's V-Twins. This sparked huge demand for these dependable units for open-class Japanese motorcycles.
STM technicians worked on the adjustability of engine braking independently from the pressure on the clutch plates, thus modulating more opening parameters of the system. To this end, new Evoluzione primary springs were developed with a greater diameter and the secondary diaphragm springs are now available with different degrees of hardness.
Like the clutch's other components, Evoluzione springs are entirely manufactured by STM and supplied with an operation graph and a serial number. The secondary spring controls the slipper function; by changing the force of the spring it is possible to adjust the slipper clutch, amplifying or reducing the effect of engine braking. The lighter the secondary spring, the less the engine braking effect, and vice-versa. Grafted from the STM's popular Ducati line is the launch control built into the CBR1000RR unit. The launch-control device is simply a sprung plate that absorbs the sudden blast of horsepower when the clutch is dumped at the start of a race.
All STM clutches are built to operate with minimal friction, assuring great sensitivity—even on wet tarmac or
other low-grip conditions. Clutch lubrication is an extremely important factor. That said, superior lubrication of the unit is guaranteed by STM's Forced Lubrication Systems. The back side of the clutch hub has grooves in it which suck the oil in and push it toward the discs. As with all STM wet-clutch applications, the clutch basket and disc pack are utilized.
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