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By RICK JOHNSON
TOO TECH SUSPENSION
BACKGROUND
A Shock Absorbers is a hydraulic device that offer resistance to motion. This resistance or “damping” is dependent on shaft movement. As the shaft speed increases, so does the damping force. By customizing the internal shock valving, a knowledgeable suspension tuner can change the relationship between low and high speed damping, but the rider has been unable to externally adjust this relationship. With the release of this new adjuster, the rider has the ability to customize his own compression damping curve.
COMPRESSION ADJUSTER
OPERATION
The shock compression stroke plunges the shock shaft and piston into a cylinder filled with oil. While the piston is traveling through the oil, the shaft is disappearing inside the cylinder. The oil displaced by the shaft moving into the cylinder travels through the compression adjuster and on to the reservoir. By restricting the oil flow through the adjuster, oil back pressure is increased which increases compression damping. The new Honda compression adjuster is capable of distinguishing between high and low oil flow rates and separately controlling each rate.
DESCRIPTION OF 1996 CR 250 HI & LOW SPEED COMPRESSION ADJUSTER (Refer to Exploded View)
As previously described, the compression stroke causes oil to flow into the reservoir. Note the ‘round’ and ‘hex’ arrows indicating oil flow as it passes through the adjuster in route to the reservoir.
LOW SHAFT SPEED ADJUSTER OPERATION
(Slow bike speed and rolling bumps)
During low shaft speeds a correspondingly low flow of oil travels through the adjuster. This low oil flow rate creates low pressure acting against both the high and low speed valves. The low speed valves are more flexible than the high speed valves so they bend first allowing oil to flow through the low speed circuit shown by the ‘hex arrows’. Additionally, the oil can flow freely out the low speed ‘bleed’ adjuster hole. If the slotted adjuster is turned out (counterclockwise), the effective ‘bleed’ hole becomes very large allowing a large unrestricted flow of oil which reduces oil pressure. Lower oil back pressure means less damping. If the slotted adjuster is turned completely in (clockwise), the bleed hole is closed causing all the oil to travel through the flow restricting low speed valves resulting in higher back pressure and more low speed damping.
HIGH SHAFT SPEED ADJUSTER OPERATION (Faster
bike speeds and sharp bumps)
As the shaft speed increases the oil flow rate increases. The supply path (orifice) to the low speed valves is designed small to create a restriction as the flow rate increases. This restriction raises the pressure. As this pressure continues to rise the stiff high speed valves begin to open and allow oil flow to ‘cross over’ to the high speed circuit. The high speed circuit resistance is controlled by the high speed valve stack and spring preload. When the Hex adjuster is turned completely out (counter clockwise), the high speed spring is loose in the adjuster and hi speed damping is controlled by the high speed valves alone. When the hex adjuster is turned in, the spring is forced against the pre-load cone which in turn preloads the high speed valves. This preload force combines with the high speed valves to increase high speed damping.
DESIGN PROBLEMS & SOLUTIONS
This excellent design concept is hampered by poor execution. Practically all mortal riders that ride the new 96 CR’s notice the bike is brutally stiff on square edges. Additionally the hex adjuster is extremely sensitive to minor adjustments. Even when the hex is turned completely out the action is still overly stiff.
The solution rests with a softer high speed valve stack and a softer high speed spring. The softer high speed stack allows oil flow at lower pressures creating a plusher high speed circuit. The softer high speed spring rate allows the adjuster to be turned in convenient 1/6 increments during compression tuning.
OPINION
When the high and low valve stacks are properly revalved, and equipped with an appropriate high speed preload spring, this adjuster is ‘very cool’. It allows the rider to reduce the low speed damping on hard packed stutter bump tracks to ride through the small ripple type bumps allowing the wheel to stay attached to the ground. When riding sandy tracks or stadium tracks with long stretches of whoops, the low speed adjuster can be turned in to increase damping and keep the bike on top of the bumps. Typically the high speed ‘hex’ is tuned after the low speed ‘slot’. This allows the high speed adjustment to complement the low speed setting to control bottoming or ‘feel’ on obstacles as required.
Too Tech Racing has this adjuster ‘Dialed In’ and is very happy with its performance!
Additionally, Too Tech Racing offers a retrofit kit for late model Kawasaki’s and Yamaha’s, and 1995 Honda’s. This kit consists of a custom machined shell manufactured by Pro Concept and modified internals from a 1996 Honda CR.