Blowing out seals is no fun and it can be avoided in most cases by selecting quality fork and shock fluids. Seal compatibility is fairly simple but very important. Reducing friction moderates heat generation and minimizes surface friction as a tuning variable making suspension tuning easier as well. If wear starts to become excessive, it can result in increased static friction and failing parts. Preventing friction and wear are important in these applications for a number of reasons. These components reduce the oxidation rate, minimize the effects of contaminants and resist permanent changes to the oil viscosity. This is because rear shocks generate significantly more heat than front forks do so the operating temperature ranges of a rear shock is very broad.įor long term damping consistency, things like stabilizing additives and shear stable base fluids keep the oil performing like it did fresh out of the bottle. Viscosity index can be an important characteristic for both fork oils and shock oils, but it is common for rear suspension oils in particular to have extremely high viscosity indexes. This measures the change in viscosity caused by temperature changes. Providing consistency in the damping force is accomplished in the short term through a high viscosity index. Reduce friction and wear between the moving parts.Provide a consistent damping force to avoid suspension fade, or in other words, to keep fork dive and suspension rebound steady throughout:.So knowing what fork and shock oils do gives and idea of how they need to perform. By slowing the up-stroke and absorbing some of that energy, the oil eliminates suspension the shock of the spring rebound and stabilizes the suspension for smoother operation. This is because the fork or shock fluid’s main purpose is to dampen the spring rebound following compression. They absorb some of the downward force in conjunction with the spring to lessen the shock on the down-stroke, but where these fluids really shine is on the up-stroke. Their purpose is to absorb and dampen the forces exerted on the suspension under pressure. Suspension fluids are basically a type of hydraulic fluid. Since forks and shocks are something I am able to constantly learn about, they remain a constant source of intrigue to me. The second reason is that no matter how much I learn about suspensions I seem to be constantly finding new ideas and information that I had not discovered before. They are straightforward to design, yet there is a lot of opportunity to fine tune and optimize a fluid for specific suspension designs. First I like the fluids for their simplicity. Suspension fluids are a topic of interest for me for two reasons.

Bel ray fork oil viscosity chart