This week on the Tuesday Tune we're delving into suspension fluids to discuss some of the demands placed on them and how the manufacturers develop the properties that are necessary to meet these demands. Since we at Vorsprung Suspension aren't chemists, we invited Alex Marangoni, Canada Research Chair, Professor of Soft Material Sciences at the University of Guelph and the scientist behind Whistler Performance Lubricants to explain a few things to us:
1. What the major demands on suspension fluids typically involve
2. What base oil types are used and their properties
3. Some of the compromises involved in oil design
4. How oil properties change with temperature and over time.
From the workshop's point of view for servicing, we consider three main factors in the most relevant priority order when selecting an oil for a given application:
1. Viscosity - how thick the oil is, and its resistance to flow through shear
2. Viscosity Index - the thermal stability of the oil and ability to minimise changes in viscosity as temperature changes
3. Lubricity - its ability to reduce friction.
Each of these factors has to be considered in terms of its relevance to the oil's application. For example, fork splash bath lubricant needs to lubricate first and foremost, and forks in general are more sensitive to stiction than rear shocks as the rear shock has the leverage of the suspension linkage to help overcome its friction. Conversely, rear shocks see more heat than forks, so thermal stability becomes a bigger concern.
Following those three primary considerations are secondary considerations, in no particular order:
1. Oil durability - oil breakdown through thermal and shear stress occurs over time.
2. Environmental concerns (side note - WPL's oils are biodegradable and non-toxic... but they taste terrible and eating or cooking with them is still generally not recommended)
4. Anti-foaming characteristics (for open bath/emulsion dampers only)
5. Other factors affecting performance such as adhesive additives ("tackifiers") that can drag oil past seals