Viscosity comparison chart pro#
Viscosity comparison chart iso#

VI = a lovely Sunday morning, the ambient temperature may be 21C (70F). The Viscosity Index is calculated as such: signifies relatively little change in viscosity over a wide temperature range.” So specifically with regard to suspension, the greater the VI, the more consistent the damping will be over a large temp change.ĪSTM D2270-04 Standard Practice for Calculating Viscosity Index From Kinematic Viscosity at 40 and 100☌ In other words, the oil becomes extremely thin at high temperatures and extremely thick at low temperatures. signifies a relatively large change of viscosity with changes of temperature. “The viscosity index (V.I.) of an oil is a number that indicates the effect of temperature changes on the viscosity of the oil. The Viscosity Index is very important in a suspension oil.

Viscosity comparison chart iso#

A very, very rough conversion table from SAE gear and motor oil grades is HERE.Ĭonversion from SUS to ISO Courtesy of Shell. ASTM D88-94(1999).Ī rough conversion table from SUS grades is HERE. Although this is slightly better system than using SAE 'weights', the Saybolt Universal Second is considered antiquated, is vague and is not a valid viscosity reference. 85/150) or Saybolt Universal Second / Viscosity Index. 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.

Viscosity comparison chart pro#

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.