Suspension Tuning and Maintenance Series:
“Hey, I need to get my suspension re-valved!” What does this mean? The suspension systems used on today’s motorcycles work very well stock for their intended use. These motorcycles incorporate a very sophisticated suspension system. An infinite number of tuning parameters including springs, oil volumes, valving and hi/low adjusters front and rear allow these suspension to be tuned to track, rider and riding styles. When the use of the motorcycle falls outside the intended area or the rider falls outside of the average, there are many avenues that can be explored to set-up the suspension. This letter will discuss what suspension valving is, some basic theory and how valving fits into the overall suspension set-up.
Valving refers to the physical manipulation of the shim stacks to achieve certain flow characteristics within a damping system. Basically as the suspension springs compress and rebound, damping controls the rate of these forces. There are two types of valving circuits, the low speed circuits, which are controlled by the clicker adjustments, and the high-speed circuits, which are controlled by the shim stacks. The low speed circuits control the damping in the first third of the travel or the “sag range”. The clicker is actually a needle and orifice much like a carburetor jet. Oil flows through the jet and the amount is governed by the restriction of the needle. Hence as you adjust the clickers stiffer you are allowing less oil to pass through the orifice and vice versa. As the suspension reacts to larger impacts, the oil flow is higher than the low speed circuit can handle the shim stacks begin to open. The valving only needs to react to the actual magnitude of the impact. Ideally the wheel should always be in contact with the ground and the bike should remain fairly level and stable. As the suspension encounters a larger impact the height speed valving controls this area. High speed and low speed circuits refer to how fast the suspension travels not to the speed of the vehicle. Transition or separator shims separate the valve stacks. The rebound valving typically is stacked to compliment the compression valving and has low speed clicker adjustments, low speed valving and high-speed circuits.
C-Cycle Suspension Service
16 West High Street East hampton, CT 06424 – 860-267-1710 – www.ccycle.com