The Effect of Inflation Pressure and Vehicle Loading on the Sidewall of a Radial Tire

-The sidewall is one of the regions where service failures occur in a pneumatic tire. Knowledge of the stresses or strains developed in the sidewall under varying service conditions is required if such pneumatic-tire failures are to be avoided. This paper describes an experimental investigation into the effect of inflation pressure, vehicle load and camber angle on the sidewall-surface strains Jn a radial tire. Photoelastic coating and a specially designed strain-gaging technique were used For pure inflation pressure, the magnitude of the measured shear strains in the sidewall is directly related to the inflation pressure. The maximum sidewall shear strains Jn pure inflation are located in the lower sidewall (18 mm from bead), irrespective of the magnitude of the inflation pressure The meridional sidewall slra~n =s predominant in the inflated but otherwise unloaded t i re The meridional strain is proportional to the square root of the inflation pressure The maximum meridional slrain is located in the mid-sidewall regton For a constanl vehicle loading, there is a transihon inflation pressure below or above which the c~rcumferential shoulder strain increases sharply Thts observation highlights the importance of maintaining satislactory inflation pressure in passenger-car tires as an under-inflaled tire will induce severe strain development at the shoulder In addition to the vehicle load. the introduction of camber angle produces localized change in the meridional and circum ferenlial strains within the contact zone The increase of camber angle up to 10 deg causes continuous increase in the meridional strain in the lower sidewall but decrease in the upper sidewall I-he mid-sidewall meridional strains remain practically unchanged The circumferential strains along the load line are. in general, lower due to the increase in cam bet angle.