Some oils are labeled on the SUS / VI (ie. SAE J300 is used to define engine oils, while SAE J306 is used to define drive line (gear) and chassis lubricants. Another point of confusion is that motor oils and gear oils are rated for viscosity on the SAE scale at different temperatures, leading to similar viscosity oils having very different ratings.

The SAE weight system has a very broad and vague viscosity range and does not even cover the viscosity range that most quality motorcycle suspension systems require. Suspension oil is labeled by weight because consumers are used to thinking of oil (ie.

Viscosity comparison chart Courtesy of Shell Oil. These problems can be seem graphically by comparing several systems to each other. This is not a judgment about the quality of these oils, just that the 'weight' label leads to a lot of trouble when trying to tune with suspension oils. For example Maxima RSF 7wt is actually lighter than Spectro 5wt and Silkolene Pro RSF 7.5wt is actually heavier than Showa SS-8 10wt. A straight line graph made from these two viscosity numbers at each temperature can give a very close approximation of the oils viscosity at any other usable temperature.ĭO NOT GO BY LABLED OIL WEIGHT! Not only is this a poor way to decide which oil to use, but each manufacturer seems to be on a different scale. Using these numbers, you can tune oil viscosity with a very high degree of precision in a specific heat range. ‘cSt’ stands for CentiStokes, an accurate dynamic measure of viscosity ( ISO 3104:1994 & ASTM D445-04). Modern fluid viscosity ratings are on an ISO VG (visocosity grade) using test standards set down by ASTM D-2422-97 (2002)& ISO 3448:1992 system of: / / VI. These forks tend to use oils in the ISO 16 range.

This is a very important bit of information for the mechanic.ĪTF is far too thick to be used in a modern cartridge damper fork. This means that if you are in Florida or Mongolia, AFT is going to be available and consistant. 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. 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.įor years, ATF has been the standard fluid for damper rod forks. 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.Įssentially, the oil is forced through an orifice or past a spring loaded shim to creating a resistive force to the action of the shocks.

9 Comercial Brands and their properties.

Honda fork oil viscosity chart