To keep your suspension riding smoothly and effectively, stay true to the recommended fork seal replacement intervals. Wetter conditions are more benign than extremely dry summer dust, which is finer and has an ability to seep past seals with greater success. Riding environment also has a significant effect on fork oil breakdown. As contaminants reach the deeper damper oil, they will accelerate molecular degradation. Even though fork seals do their best, containment ingress remains inevitable. How do you keep your fork oil in the best condition? Maintenance is the obvious action. This generates heat and the better your fork oil is at resisting the breakdown of its own molecular structure under load, the more fade-free and consistent your mountain bike’s suspension performance will be. If you are impacting roots and rock gardens at speed, and your suspension is dramatically cycling through its travel, oil is being forced and recycled via the shim stacks with great force and frequency. You could think of the centistoke value as being an expression of your fork oil’s thermal stability or viscosity. What makes a good fork oil? The centistoke rating is a viscosity coefficient and suspension engineers meticulously test their systems and then recommend a specific centistoke value. When you desire that suspension sensitivity over the slightest of bumps, or controlled compression when you roll down a steep sequence of rocky steps, it is all a function of having quality fork oil flowing optimally through the damper’s shim stack. The quality and condition of your mountain bike’s fork oil is influential on how comfortable and responsive it will be to ride over technical terrain. How your fork oil moves through these stacked ports, is what makes a fork feel buttery smooth or harsh and rubbery. The shim stack is made up of different sized discs, to allow for fluid flow.

Taming terrainĬontrolling the speed and feel of your fork’s compression are the properties of fork oil moving through shim stack in the damper. To reduce the stiction (‘friction’) that inhibits a fork’s movement, its seals are oil lubricated, making them slipperier, without diminishing their inherent protective function.īeyond the lubrication function, fork oil is what regulates the initial movement on your mountain bike’s suspension.

Fork oil kinematic viscosity chart