In this paper, a novel application of a soft sensor via Neural Networks is proposed. One of the most critical issues in the car is the area where the tires are in contact with the ground, these are the only points of contact between the vehicle and the road. The importance lies in the fact that keeping the tire contact patch within the operational parameters ensures the safety, comfort and maneuverability of the vehicle. There are some techniques to measure the tire contact patch, but the operating conditions of the car make impossible the implementation; so in this work the tire contact patch is obtained by the frustrated total internal reflection phenomenon and with the measures of 12 sensors in the car, a Neural Network is trained and tested. Thus, a soft sensor that accurately estimates this variable is the main contribution of this work.