Experimental load rating, utilizing strain measurements obtained under controlled vehicle loading, allows for the structures capacity to be determined. This is particularly important for older bridges. However, deterioration can often hinder the load transferring capabilities of the bridge. This results in weaker signal strength at girders farthest from the applied loading. If this is not recognized the results from the load testing and subsequent load rating may prove erroneous. This paper discusses the accuracy of one particular parameter, the neutral axis of bending based on the ability of the structure to adequately distribute the load. Two separate multi-girder/stringer bridges at different periods of their service life were tested using a custom developed wireless sensor system under various loading scenarios. The neutral axis and load distribution factors were acquired using standard department of transportation practices. The results show the ineffectiveness of the deteriorated bridge to transfer the load to resulting in highly variable measures of the neutral axis at girders farthest from the loading. However, this variability was minimal in the newer bridge.