29 June, 2012
Piston & Shim Technology
The use of thin steel shims is critical to the feel of any high-end suspension system and especially with the new DVO products. Our forks and shocks will be finely tuned with a generous combination of shim stacks to provide that stable and predictable suspension feel for both compression and rebound. Shims are used to restrict oil flowing through the holes or ports in a piston. Shims are configured in various diameters and thickness to achieve specific results as a “shim stack”.
The larger diameter shim that sits on the piston surface is the first shim to resist oil flow and generally affects the low-speed compression. The shims that are in the middle and farthest away from the piston’s surface affects the mid-high speed compression feel. When proper shim stack settings are achieved the end result is a bottomless feel on compression and a controlled/predicable extension that works in concert to keep your wheels planted on the ground. The main reason shim stacks are so amazing is that they are dynamic or speed sensitive and a proper stack can deliver a wide range of damping performance purely based on velocity.
Many companies use orifice or small holes to control compression and or rebound in their dampers, especially on lower end products. There are serious limitations to orifice dampers, under low speeds oil can easily flow through a hole but when speeds increase, oil flow becomes restricted and hydraulic locking occurs. Thats where a harsh feel on compression occurs or an unpredictable hopping of the front wheel on the rebound stroke can occur reducing traction and control.
Shim stacks can be configured in hundreds or thousands of different combinations. There are “straight stacks,” tapered stacks,” “cross over stacks,” “gap shims,” “pressure shims,” etc.
The proper use of shim stacks and piston design can yield amazing performance results and we at DVO will put our 80 plus years of suspension experience into each and every design.