Fluid properties

The variator is able to transmit power across the oil film because of the special properties of the traction fluid.

The long chain molecules used in traction fluid interlock with each other when the fluid is compressed, becoming highly viscous (glassy) under pressure. This means that as pressure is exerted at the contact points between the rollers and the discs, the oil resists the tendency to slide and transmits the power effectively. Traction fluids are typically based on synthetic oils and have been developed over past decades to fulfil several conflicting requirements simultaneously:

• Improved traction qualities (typically three to five times that of normal lubricants)
• Minimum viscosity (thinner) at cold temperatures to improve circulation
• Maximum viscosity (thicker) at elevated temperatures to improve load bearing
• Minimal chemical interaction between constituents of the oil and adjacent metal surfaces (thus improving fatigue life)
• Provision of lubrication and heat dissipation, like a normal transmission oil