Your suspension system relies on the fluid in the damper to controll its fuction and in doing so is worked increadible hard through a system of ports and valves and should be seen as a perishable component that needs to replaced regulally.
Servcie intervals will differ from manafacturer to manafacturer and from tune to tune. A firmer tuned suspension system will crate higher pressure in the fluid and will need to be replaced more often. Also air sprung rear shocks have a bigger temprature change again working the fluid in teh damper harder.
Most fork oils will come with a rating of their weight. This refers to how thick the oil is otherwise known as its viscosity. As an example; If water is 0 and tar is 100 you start to get an idea of what thickness 5 weight oil will be.
Most manufacturers will recommend an oil weight for their forks but you can use different weight fluids to change the characteristics of the damper. A thicker weight oil will create greater resistance in a system and a thinner oil will create less resistance and less damper force.
Heat can effect oils dramatically and as an example some lubricants can double in viscosity with only a 5 °C change.With this in mind you can appreciate that air sprung rear shocks create heat which can effect the viscosity of the damper fluid causing inconsistant damping effects on long descents.
You can mix oils to obtain a diluted weight. However if you mix 10wt and 5wt you won’t necessarily get 7.5wt because you have to take into account the laws of dilution, volume percentage and molarity and is a very exact science if you want a specific oil weight.
All of these fluids are desighned to work in a particular enviroment and most are fully synthetic for this reason. For insatnce damper fluid wont work particulally well as an air spring lubricant and we allways recomend using the manafacturers fluids over aftermarket fluids or silicon lubricnats. Check our our store for more suspension lube products!
Most suspension fluids have been designed to resist foaming or cavitation.Cavitation occurs when a liquid is subjected to rapid changes of pressure causing the formation of cavities in the lower pressure regions of the liquid.
Simply put, the fluid turns into bubbles or foam. Bubbles have very little use in a damper offering little or no damping characteristics. Manufacturers of suspension fluids work very hard to minimize this cavitation in the fluid.