STM Design:

All STM parts start with an in-depth, comprehensive design process. Every aspect of the part’s function and life are scrutinized, with special consideration given to performance. Together with involvement from our numerous factory race team partners, we strive to produce the most technologically advanced parts available on the market. Our parts are not only beautiful to look at, they are the highest quality, most durable, and peak performing parts money can buy. All STM parts are constructed from the highest grade of raw materials. They are CNC Machined to the tightest tolerances and our clutch components are hard coated to ensure longevity. Once completed, STM parts undergo maximum scrutiny in the toughest torture environment… the racetrack. Through over a decade of direct race involvement at the world level, STM parts have been refined and perfected .

SLIPPER CLUTCH TECHNICAL

SPRING FUNCTIONING

Primary spring:
• It applies pressure on the disc pack through the pressure plate;
• It replaces the many helicoidal springs.
• Allows adjustment when Motor performance is increasing.

Secondary spring:
• it applies pressure on the drum;
• it regulates the opening of the slipper clutch and regulates the engine braking to the wheel.
• It allows adjustment to rider preference - The lighter the spring, the less engine brake; the heavier, the more engine brake.

Primary Spring function:
• The primary and secondary springs are pre-loaded in order to generate an initial elastic strength of contrast.
• When you operate the clutch lever, the primary spring is compressed. The spring releases an elastic strength relative to the lever movement.

Spring adjustment:
• STM 125mm diaphragm primary springs are offered in 10Kg increments and are changed as Horsepower increases. There are 13 different weights to choose from (sold individually).
• The 85mm diaphragm secondary springs are offered in 10Kg increments and are changed to rider preference and surface conditions. There are 6 different weights to choose from (sold individually).

HOW DOES SPRING LOAD CHANGE WITH COMPRESSION?

On closing the Throttle or changing down in gears, the engine's compression passes from the Cylinders to the gear box forcing the Clutch drum to rotate, with this action the secondary spring shifts the Clutch Hub outwards causing the clutch discs to disengage and moderate the compression shown at the rear wheel. The secondary spring is compressed in comparison with the initial drive and generates an elastic strength of contrast until power resumes. When power resumes to drive forward, the secondary spring to close the discs and start driving again.

ARE STM SUPPLIED WITH A SUITABLE SPRING SET UP?

All STM Diaphragm Slipper Clutches come with Primary & Secondary springs that have been calibrated for the specific application the clutch is intended for. The standard weight of both springs chosen by the STM Factory Technicians to be suitable for 90% of riders. One of the outstanding features of STM Slipper Clutches is that they offer a wide range of adjustment to suit any rider's needs. Both Primary & Secondary springs (weighted in Kilograms) are offered in 10kg increments and sold individually. Riders & engine builders can purchase additional springs to find the perfect combination to suit the rider preference and Horsepower output.

ARE THEY THAT GOOD FOR OFF-ROAD USE?

The STM Off-Road Wet Slipper Clutch is specifically designed for 250cc & 450cc four-stroke wet clutch applications. The clutch uses the cornerstone of STM technology, the 'Ball & Ramp' actuation for smooth slipper clutch operation along with STM's exclusive 'Forced Lubrication System' (FLS). STM developed the Forced Lubrication System to increase the amount of engine oil flowing through the wet clutch, this leads to cooler running temperatures and cleaner conditions therefore increasing the performance and longevity of the clutch components. In addition, the STM Off-Road Wet Slipper Clutch uses a 121mm Diaphragm Primary Spring and an 85mm Diaphragm Secondary Spring. By using diaphragm springs in both the primary and secondary positions the STM Off-Road Wet Slipper Clutch offers superior adjustability to suit any riding style and engine modification.

DIFFERENCE BETWEEN 90mm & 125mm PRIMARY SPRING.

The main difference is that with the 125 mm spring clutch, the elastic action of the spring is applied right on the disc pack. With the 90mm spring the pressure is not direct on the plates, because the spring is positioned in the centre of the clutch. The advantage of 125 mm spring is to give a softer clutch lever. The slipper clutch with a 125 mm spring is a later version of the 90 mm spring Slipper Clutch.


 

ABOUT STM.

STM's slipper clutch represents a huge change in motorcycle technology and rider technique and thanks to STM innovative ideas, worldwide success for the riders using the STM product. Thanks to the competence and lengthy experience gained designing and machining high quality components, the company has became the LEADER in the performance CLUTCH market segment. Thanks to STM, the slipper clutch era had begun.

The first STM slipper clutch prototypes were originally developed and tested with the Official Ducati World SBK Team. These prototypes soon contributed to the victory of two World SBK Championships.

Development and tests carried out in the following years allowed STM to extend such technology to wet clutches. In 2003 the "Evoluzione" slipper clutch technology was applied to wet clutch systems on Japanese motorcycles, widely broadening its range of applications with cooperation with top Honda, Suzuki, Yamaha, and Kawasaki teams that compete in sport production competitions. This allowed STM to gain experience and improve its product. Then STM debuted in Motocross and Supermotard meetings with unanimous approval and contributing to the victory in many races.

Today STM offers a broad range of products which are constantly being tested and improved in order to satisfy the requirements of a growing number of riders. Developed and tested in cooperation with top teams, all STM components are designed with the latest technologies and manufactured with the most advanced CNC machinery.

STM "Evoluzione" clutches stand out for their technologic and highly innovative design: shaped by their own function to essential lines, they are precious objects, a state of the art expression of Italian design.