Why Do Tire Tread Patterns Make Noise?

All tires generate noise as air flows through their tread grooves and they roll into and out of contact with the road. Tire designers have to balance tread design noise with service-appropriate traction, for example, wild looking tread designs that deliver aggressive off-road traction are more likely to growl on the highway, while mild tread designs that offer reduced on-road noise may sacrifice foul weather traction in wet and wintry conditions.

Partnership

Tire noise is dependent on a partnership between the tread pattern and the surface it's driving on.

Roadway surfaces influence both the intensity and spectrum of the sound generated by the tire/surface interaction. Changes in audible sound can often be heard as tires drive from concrete to asphalt roads, or from smooth to coarse surfaces. Spacerless concrete and new asphalt roads tend to be the quietest partners and provide the truest test of the tread pattern noise actually generated by the tires.

If a driver senses new tires generate the same type of noise as their previous tires, it is likely the noise is actually the result of the road surfaces they drive on. While some drivers think their tires are noisy, they may not realize it's the road surface that's actually responsible.

The tire designers' and engineers' goal is to vary audible tones until the tires generate a pleasant "white" noise.

Pitch

The tire industry uses the term pitch to describe the number of tread blocks around the circumference of the tire. As a general rule, summer performance tires feature larger tread blocks and fewer pitches to enhance steering response and handling, while winter tires feature smaller tread blocks and more pitches to increase the number of biting edges that enhance traction in snow and on ice. All-Season tires fall in the middle.

Pitch Sequencing

It's not desirable for all pitches to be created equally. If every tread block (pitch) featured the exact same size and shape, each one would generate the exact same sound tone and intensity as they rolled through contact with the road. This would result in all four tires contributing to an unpleasant monotonous tone.

The different pitches/placement of Pirelli Cinturato P7 All Season Plus tread blocks are highlighted by different colors.

In order to keep that from happening, tire designers use computers to sequence multi-pitch tread designs that subtly vary tread block size and shape to randomize the road contact and resulting noise. They also offset circumferential block placement of neighboring ribs to reduce noise by aligning lateral grooves with adjacent tread blocks.

The tire designers' and engineers' goal is to vary audible tones until the tires generate a pleasant "white" noise.

Preventative Maintenance

Depending on their diameter, tires roll about 800 times per mile. And on every revolution, the leading edge of each independent tread block collides into contact with the road, followed by the rest of the block until the trailing edge is released from contact a fraction of a second later. Happening about 4 million times in just 5,000 miles, this recurring in-and-out-of-road contact has been shown to promote irregular tread wear. If not stopped, irregular wear is likely to change the size and shape of the tread block contact and undo the engineering that made the tire design quiet in the first place.

Since it's important to promote even wear, periodic tire rotation is important preventative maintenance that every tire needs. Periodic tire rotation shares the work and the wear between all of the vehicle's tires and results in non-directional tires rolling in both clockwise and counter-clockwise directions.

Because every tire's tread is its deepest and the most susceptible to irregular wear when new, the first tire rotation is the most important one and must be completed before the tires have been driven 5,000 miles. Unfortunately, as engine oil change intervals have climbed, it's probable the first tire rotation will be required as a stand-alone service.

NOTE: Skipping tire rotations is likely to promote irreversible irregular tread wear patterns that will increase noise over time.