The tire is the main interface between the vehicle and road, and all maneuvers controlled by a driver to road vehicle are achieved by the interaction force between tire and road. In modern vehicle design, tire modeling plays an important role in effectively assessing vehicle handling, ride comfort, and road load analysis. The long term goal of this research is to develop a three-dimensional robust tire model that can be used for road load durability simulation. This work is the first step to the long term goal. This paper presents a new simplified in-plane tire model based on a traditional rigid ring tire model. The interaction between the tire and road is assumed to be patch contact. Optimization technique is used to obtain all key tire parameters of the tire model by minimizing the vertical and horizontal contact forces between the model simulation results and road test data when a tire passes a road bump. After the parameters are identified, a full factorial design of experiments with three levels for each of 8 parameters (horizontal spring stiffness and damper coefficient, vertical spring stiffness and damper coefficient, rotational spring stiffness and damper coefficient between the rim and ring, ring radius, ring residual spring stiffness) is conducted for parameter sensitivity analysis. The three levels for each parameter except the ring radius are 50% increase, 50% decrease, and nominal values. Sensitivity analysis has shown that several parameters are critical to the peak value of the vertical and horizontal contact forces. A quarter-car model is then used to assess ride comfort of the vehicle suspension system. The quarter-car model with the proposed tire model can more accurately predict the ride comfort subject to random road inputs than the one with point contact tire model.