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Worldwide Tire Surveys
Walter H. Waddell*, R. Christopher Napier and Dirk F. Rouckhout
ExxonMobil Chemical Company,5200 Bayway Drive, Baytown, TX 77520, USA
Ref: 2014.1007
The inflation pressure of the tire impacts all aspects of its performance: handling, treadwear, durability, and rolling resistance. Halobutyl rubber is the polymer of choice to be used in the innerliner compound due to its excellent air and moisture impermeability, and its resistance to flex-fatigue and oxidative aging. During the last 15 years, a number of surveys of passenger car radial tires have been performed to identify those features in the innerliner area that relate to improved tire performance. 150 tire brands from 30 manufacturers around the world have been evaluated and will be discussed. Properties measured include innerliner gauge and composition (polymers, fillers), and liner cushion gauge and its construction.
Tire performances measured were inflation pressure loss rates, roadwheel durability, and more recently rolling resistance due to the mandatory government regulations now in effect to label tires. Properties and performance of tires varies widely between different companies, among different regions within a company, and/or among multiple brand names within a company. Using computer analysis, statistically significant trends were identified and are shown. For example, performance is different for tires manufactured in different regions of the world (namely the Americas, Asia-Pacific and Europe), by a Top 10 company (based on total sales), and/or when manufactured as an original equipment versus a replacement market tire. Since tires are a globally traded commodity, where the tire is purchased can show different trends from where it is manufactured. For example, tires manufactured in the U.S. have the thickest cured innerliner gauges, the highest halobutyl rubber (phr) and halobutyl content (% in the formulation), the highest effective halobutyl rubber level (content multiplied by innerliner gauge), and gives the lowest inflation pressure loss rate values (IPLR). Similar trends are observed for tires manufactured by Top 10 companies and also for tires made for the original equipment market.
Changes to the innerliner and liner cushion gauge and in the construction of the liner cushion can be observed during this 15-year time period. Construction changes include using no liner cushion, the liner cushion being continuous from bead-to-bead between the innerliner and the carcass, the liner cushion being placed from shoulder to shoulder, or placed only as strips in the shoulder areas. Some changes probably result from use of newer manufacturing equipment that help minimize the cord penetration into the innerliner, thus resulting in a more uniform thickness and improved tire air retention.