Suspension Fluid

What does the Suspension Fluid do?

In addition to providing a lubricating and cooling bath for the dampers and bushings of the fork and shock to function in, the suspension fluid is the medium that is used to provide damping in a modern system.

Essentially, the oil is forced through an orifice or past a spring loaded shim to creating a resistive force to the action of the shocks. Aside from other changes that effect damping, the viscosity of the oil and how the viscosity changes as the oil heats up will be large factors in the system.

Automatic Transmission Fluid (ATF)

For years, ATF has been the standard fluid for damper rod forks. Why? Of all the commonly available automotive fluids capable of being used in the system, ATF is manufactured within a very, very tight and suitable viscosity range, esentially ISO 34.

This means that if you are in Florida or Mongolia, AFT is going to be available and consistant. This is a very important bit of information for the mechanic.

ATF is far too thick to be used in a modern cartridge damper fork. These forks tend to use oils in the ISO 16 range.

Viscosity (ISO)

Modern fluid viscosity ratings are on an ISO VG (visocosity grade) using test standards set down by mystore ASTM D-2422-97 (2002)