Tires are asked to accomplish many tasks such as generating low noise, providing long tread life, providing flexibility to subsume fixed objects while maintaining ride comfort, maintaining lateral traction control, resisting heat build-up, responding to steering maneuvers, maintaining high speed performance, as well as braking control. These needs are addressed by the design team within a tire company. A tire must perform all these tasks while being operated under varying weather conditions. The tread grooves act as a vehicle to wick away water, allowing the tire to interact with the roadway, free of water. Without proper water dispersion, the tire will not perform its requested tasks and subject itself to hydroplaning.
A hydroplaning vehicle is one that is sliding because it has lost friction from one or more of its tires. Without friction, the vehicle is subjected to a loss of lateral stability and could result in a loss of control. A loss of traction is dependent on a wide variety of factors, including the tire tread design, the tire’s air pressure and loading, along with the roadway composition, including micro and macro texture quality, contaminants such as oil and water levels. A vehicle’s suspension, weight, center of gravity and speed also influence a tire’s ability to maintain optimal friction.
A tire design, particularly its tread design, can be maximized to ensure optimal friction, but the ‘trade-off’ might result in a stiffer ride or diminished speed capacity. For instance, a tire marketed for optimal performance in snow is constructed with wider grooves in its tread. These wider grooves improve a tire’s ability to disperse moisture, but it also results in diminished speed capacity. A snow tire does not perform as well on dry roads as a tire designed without that added feature.
Tire designs are tested on dry and wet roads. Whether it be maintaining a tight curve or braking, all tire designs are tested to achieve optimal friction under wet and dry conditions. During a braking test, a vehicle’s brakes are abruptly applied, which slows the rate of the tire compared with the vehicle speed. This contrast results in “slip”. Percentage of slip is measured by calculating the vehicle speed minus the tire speed, divided by the vehicle speed, multiplied by 100.
Tire manufacturers test tires in hydroplaning conditions. Hydroplaning can result when a tire travels over an accumulation of water. Speed is always the most important variable to avoid hydroplaning. Increased speed equates to an increased amount of water in front of the tire’s footprint. This “wedge of water” results in the forward part of the tread failing to come into sufficient contact with the roadway, decreasing the length of the footprint on the roadway. This loss of friction compromises a tire tread’s ability to wick away water between the road and the tread. Water acts as a lubricant, preventing the traction necessary for safe operation.
Your tire’s design helps prevent hydroplaning. While speed is important, optimal tread depth is vital. For this reason, tires with a tread depth of 4/32nds or less should be discarded.
Written by:
Guy L. Watts, II
Watts Guerra LLP
4 Dominion Drive, Bldg 3, Suite 100
San Antonio, Texas 78257
Phone (210) 447-0500
© Watts Guerra LLP 2015
