Effect of Tire Construction on Inflation Pressure Loss Rates

The inflation pressure of the tire generally impacts the rolling resistance, treadwear, handling, and durability of the tire.  Halobutyl rubber is the polymer of choice in the tire innerliner compound due to its excellent air and moisture impermeability, and resistance to flex-fatigue and oxidative aging.  The inflation pressure loss rate (IPLR) values measured following ASTM F-1112-06 procedures have been shown to have an excellent correlation to the oxidative aging of the NR wire coat compound and to the durability of passenger tires when tested on a 1.7-m laboratory roadwheel.  Experimental passenger tires were previously made with innerliner compounds having varying amounts of bromobutyl rubber (BIIR) and natural rubber (NR).  Present results correlate the IPLR values to tires made (1) with innerliners having varying thicknesses, (2) with and without a liner cushion compound, and (3) with the cushion continuous from bead-to-bead or only being placed it the shoulder areas.  The effects of tire construction on the innerliner flow and the cord penetration are shown.