Tire Contact Patch

What is the Contact Patch of a tire?

All living beings leave their footprints, the traces of which could be seen while walking on sand, mud, or even when stepping on wet paint. Similarly, our car also has a ‘footprint’ which is called a ‘contact patch’. If the vehicle is placed on the glass floor, you could see four patches of rubber (one from each tire) from below. The contact patch is the only point of contact between the vehicle and the road. It is surprising to realize that the size of a contact patch is typically about the same size as our hand. Yes, you read it right. This small area of contact patch determines the performance of a vehicle. Let's get to know the contact patch in more detail below. 

How does the Contact Patch impact a vehicle’s performance?

Before we move forward, we need to understand that the contact patch is not something that is added to the tire during manufacturing. It is a flexible area that occurs when the load on the tire keeps changing as the vehicle goes through the start, stop, and cornering maneuvers. 

Many vehicle attributes are influenced by the ability of the tire to manage load through a contact patch. These performance attributes are traction, handling, ride quality, steering responsiveness, tread wear, and tire noise. It also helps to cushion the vehicle from road impacts. 

While driving, these contact patches act as a source of information that sends feedback to the driver via the vehicle’s performance on the road. A driver might need some technical knowledge to interpret the performance feedback. The Cerebrum Sensor’s intelligent system collects raw data from these performance attributes (ones which matter the most) and summarizes useful results in a clear visual representation on your mobile application. 

Variables that impact the Contact Patch area

Some of the important variables that affect the contact patch area and the related performance attributes are discussed below:

Pressure

It is advised to inflate the tire based on the manufacturer’s recommended tire pressure to achieve the tire’s adequate load carrying capacity and optimal vehicle handling. The manufacturer’s recommended pressure could be found on the vehicle information placard located on the driver door panel. An overinflated tire creates comparatively less contact patch area and this results in reduced tire traction.

Similarly, an underinflated tire creates a larger contact patch area and results in more traction. Max traction does not mean max performance. More traction means more friction and needs more power from the engine to push the vehicle forward. Underinflation also accelerates tread wear at the edges.

Load

Tire contact patch areas change as the forces on tires change. Load changes as the vehicle go through the start, stop, and cornering maneuvers. The number of passengers and luggage in the trunk also changes the weight distribution in the vehicle. Vehicle manufacturers provide recommended tire inflation pressure, tire alignment specification, and select tire size to deliver an optimized tire contact patch as the vehicle goes through dynamic load changes. 

Tread Design/Grooves

Tires come in various tread designs and grove thicknesses based on the purpose it is made to serve. Grooves in tires help to expel water from underneath the tire. This avoids hydroplaning and saves tires from slipping. Off-road tires are typically equipped with wider and deeper grooves to withstand mud, sand, snow, slush, and water. Wider grooves create less contact patch but then these tires are made much wider to provide a good overall area of the contact patch. Performance tires and ‘summer tires’ on the other hand have shallow treat depth and fewer groves to create as much contact patch area as possible. All-season tires generally come with moderate tread depth and enough grooves to reliably and safely operate in a wide variety of weather conditions. 

Impact of tire rubber material on the Contact Patch

Why is it advised to use specific tires for harsh summer and winter conditions? What exactly is the difference between summer, winter, snow, and all-season tires? The answer to these questions lies in the traction force between the road and a contact patch. Softer rubber compounds offer the most traction. That’s why the racing tires are made out of a really soft compound but last only for one race. Daily driving tires need a good balance between grip and durability. 

The rubber compound in winter tires is formulated to stay soft and grippy at low winter temperatures. Snow tires usually use the winter compound but have more chunky tread patterns providing extra grip at the contact patch when driving through snow, slush, and black ice. The rubber compound in summer tires is relatively harder to withstand high temperatures from the sun and friction at the contact patch. Using summer tires in the winter weather hardens the rubber and the contact patch loses grip with the road. This results in losing control over your vehicle and can lead to serious injuries or worse. All-season tires, on the other hand, provide a good balance between the summer and winter compounds. 

Now you know how important of a role the contact patch plays to provide a safe and grippy ride. Don’t forget to add a set of Cerebrum Intelligent Sensors and explore using our iOS mobile application how this technology converts the raw data from performance attributes into useful results. Last but not least, make sure to physically inspect your tires every month to maintain a healthy grip at the contact patch.