Accurate tyre models are essential for all full vehicle simulation models. Tyre models are usually parameterised based on measurements on new tyres. This article performs a sensitivity analysis, based on experimental data, to determine the effects of age and wear on a 235/55R19 tyre’s stiffness characteristics as well as the effect of wear on the tyre’s longitudinal friction characteristics. A well-researched and documented method was used to artificially age the tyres. Static tests were performed periodically on the tyre to monitor the changes in stiffness characteristics. Tyres were also subjected to accelerated wear by performing repeated side force versus slip angle and longitudinal force versus slip tests on a coarse concrete surface. The results indicate that the vertical and longitudinal force versus displacement characteristics have small but convincing dependencies on the age and wear. While the aging process was a trustworthy method, the wear process created irregular lateral and circumferential wear which impacted results. Overall the effects of age and wear did not exhibit substantial enough influence on the tyre stiffness to merit a full tyre model update. However, the wear did have a significant effect, in the order of 10%, on the longitudinal friction of the tyre.