Hyper Racer - Copyright © 2009 - Dean Crooke


STM Slipper Clutch

The slipper clutch that started it all!

STM Slipper Clutches are beautifully fabricated in anodized aluminium alloy and titanium. These are exactly the same STM clutches that are used by Ben Bostrom, Noriuki Haga, Franki Chilli, and many other top motorcycle road racers world wide.

ALL STM Clutches are made IN HOUSE at the Italy Shop, with the highest tolerance and quality control.  Each part is stamped with a part number and serial number to keep quality control and records of all parts made. This insures that the clutch fitted to your Hyper PRO Racer is the best product available.

The STM slipper clutch offers two major advantages; to assist the driver with vehicle control and help prevent damage to the engine and gearbox.

Going faster is not just about HP, it's about smoothness and traction. It's about the drivers ability to load up the tires to their limit of grip and keeping them there, just before the point they let go.
What you do not want is the rear tire losing traction due to engine compression braking, while braking and changing down gears on entry to the corner. The slipper clutch assists the driver by reducing the effect of engine braking. Engine compression braking causes the rear wheels to ‘lock up’ when braking hard for a corner. A driver that is too aggressive in this situation suffers, because the rear wheels lose traction, making continued braking and direction change much harder to accomplish.

The STM clutch also helps save the engine and gearbox, again by reducing engine compression braking. Most race engines have a rev limited, to stop the engine exceeding a certain speed considered safe by the manufacturer. This works fine when the engine is under power, but if a driver is approaching a corner, close to the r.p.m. ‘red line’, and then down-shifts, the engine can easily be forced to a speed it was never designed to reach, often with catastrophic results. Additional benefits are realised as the gearbox suffers less abuse for the same reasons, and it is less
important for the driver to provide perfectly co-ordinated gear changes.

"After years of experience and satisfaction in the production of competition engines components, STM Slipper Clutches uses the same technology, which has been already used on dry clutches, on wet clutches, too. Result: performances get better, components lubrication increases the efficacy of the system. This system, working with steel balls and ramps, helps the pilot while turning avoiding the rear wheel to slip during an hard braking. Also if you use it on every day roads, there are some advantages: it avoids dangerous skidding, it increases safety and protects the internal parts of the engine. It avoids extra strokes, and reduces tyre wear of the rear wheel.
All components come from STM Slipper Clutch, is  made with the most sophisticated machines.
For the production STM Slipper Clutches selects the best aeronautical alloys and the best suppliers for surface treatments. Drum and hub are realized in Ergal 7075 and oxidized to last long.
Also the pusher plate is in 7075, but it has a steel ring which gives a stiff support to the Diaphragm Evoluzione spring . This spring is the real heart: it is possible to choose between different kind of hardness and adapt the clutch to pilot's needs. Pusher plate kit, with the function of checking plates opening is completed by a brass bearing rest holder and a pusher spring hub in steel and nitride coating. This treatment helps steel components to last longer, increasing surface hardness. STM Slipper Clutches kit assembly uses original Friction Plates, Drive Plates and basket."

Selected for use by Ducati's World Superbike team and AMA Factory Yamaha's, STM Clutches are also used by the majority of World Superbike, and Moto GP Teams