Editing Contact patch (section)

===Pneumatic rubber tires===
The size and shape of the contact patch, as well as the [[pressure distribution]] within the contact patch, are important to the [[ride quality|ride qualities]] and [[automobile handling|handling]] characteristics of a vehicle. Since the wear characteristics of tires is a highly competitive area between [[tire manufacturing|tire manufacturers]], a lot of the research done concerning the contact patch is considered highly proprietary and, therefore, very little is published on the subject.

Because pneumatic tires are flexible, the contact patch can be different when the vehicle is in motion than when it is static. Because it is so much easier to make observations of the contact patch without the tire in motion, it is more common to conduct studies of the static contact patch.

Statically, the size, shape, and pressure distribution are functions of many things,<ref>Summary Report: Evaluation of Tire Size and inflation Pressure on Tire Contact Stress and Pavement Response by Emmanuel Fernando, August 2006.</ref> the most important of which are the load on the tire and the [[Cold inflation pressure|inflation pressure]]:

* The larger the load on the tire, the larger the contact patch. 
* The larger the inflation pressure, the smaller the contact patch.<ref>{{cite web
| url = http://www.safetyresearch.net/Library/NHTSA_Pneu_Tire.pdf
| title = The Pneumatic Tire
| publisher = [[National Highway Traffic Safety Administration]]
| author = M. G. Pottinger
| date = February 2006
| pages = 335–336
| quote = Increasing inflation reduces the size of the footprint
| accessdate = April 7, 2018}}</ref>

These two properties are not [[linearity|linearly]] [[proportionality (mathematics)|proportional]] to the [[area]] of the contact. For example, a 10% change in load or inflation pressure usually does not result in a 10% change in the contact patch area<ref>Summary: Inflation Pressure Retention Effects on Tire Rolling Resistance, Vehicle Fuel Economy and CO2 Emissions presented to the California Air Resources Board July 4, 2008 by Walter Waddell</ref> because the load or pressure on a tire can be altered freely, and the contact patch area is affected by the tire geometry and stiffness. Further, the size of the contact patch cannot be simply calculated as load divided by inflation pressure, and the average contact pressure a tire has with the road surface is not equal to the inflation pressure.<ref>Truck Tire Types and Road Contact Pressures, by Pedro Yap, June 1989</ref>