It is well known that tires wear out their tread depth as they travel, and losing tread depth changes the performance of the tire. If there was a way to not lose tread depth, it would be much better; but unfortunately, such is the nature of rubber in relation to the road!
Tread Depth
For consumers, tread depth is the vertical distance from the top of the tread block to the deepest area of the tread (called the groove, channel, or tread void of the tire). Tread depth can vary depending on which groove is measured.
Generally, the tread depth is deepest in the center of the tire and lowest at the shoulders. Depending on the tire's application and engineering requirements, its tread depth can be the same across the entire tire tread. Tire manufacturers typically list the deepest tread depth in their specifications.
Tread Depth and Performance
It is easy to assume that deeper treads are better for tires-they have more rubber to wear and therefore last longer. While this may be true for some aspects of performance, it may not be true for others. As we said before, tire design is a balancing act: improving performance in one area often leads to degradation in another.
Tread Depth, Endurance, and High Speed
In the tire world, we often discuss the effects of tires on braking, ride, handling, and wear performance, but rarely discuss endurance and high-speed performance expectations. Tires need to withstand long periods of operation in harsh environments, often at high speeds.
Tread depth, especially in the shoulder area, causes tires to run at higher temperatures because the rate of heat transfer from the inside to the outside is reduced, and higher temperatures reduce tire durability and high-speed performance.
Tread Depth and Rolling Resistance
To ensure very good rolling resistance performance, tires need to generate minimal heat and friction and have excellent heat dissipation capabilities.
None of this can be achieved with additional tread depth. More rubber in a tire means more heat generation, higher friction, and less heat dissipation. This is why increasing tread depth, especially in the shoulders, increases rolling resistance, resulting in reduced fuel efficiency. While tread compound technology in recent years has reduced the disadvantages of increasing tread depth, the challenge of improving rolling resistance in tires with higher depths remains.