Noise level is one of the key factors affecting driving comfort. As the popularity of quiet electric cars increases, more and more drivers have taken an interest in tire noise, for example. External rolling noise and interior noise are different things, but you can reduce both by keeping your car and tires in good condition. Nokian Tyres considers the noise aspect carefully in R&D and testing.
As consumers shop for new tires, it is very difficult to know which of the available options would be the quietest on their vehicle. Tire noise is affected by several factors, such as the model and type of the vehicle, the rims, rubber compound, road, driving speed, and even the weather. There are even differences between similar cars, making exact comparisons only possible in situations where the same car is used under identical conditions.
Some general assumptions can be made, however: The softer the tire’s tread compound, the more it is likely to reduce noise. High-profile tires are also generally more comfortable and quiet to drive than low-profile alternatives.
Summer and winter tires have the EU tire label that indicates the noise level. This label, however, only covers external rolling noise. External rolling noise and interior noise may even be polar opposites, and reducing one may increase the other.
“What you hear inside the vehicle is a combination of many things. Tire noise originates from the tire’s contact with the road: roughness causes the tire body to vibrate as the tire rolls over it. From there, the vibration travels a long distance through the tire, rim, and other vehicle structures into the passenger compartment, where some of it turns into audible sound”, says Senior Development Engineer Hannu Onnela from Nokian Tyres.
Tests require gauges and human ears
So far, Nokian Tyres has been performing noise tests on its track located in Nokia. The new testing center completed in Santa Cruz de la Zarza, Spain has a 1.9-kilometer “comfort road” track that offers even better testing opportunities than before. The facilities in Spain allow for testing tires on different types of asphalt and rough roads, as well as crossing cobblestone streets.
“The gauges do not tell us everything that we need to know, so we also perform a lot of subjective testing based on human assessment. It is important to find out if a noise is disturbing, even if a gauge cannot detect it”, Hannu Onnela explains.
Tire design always means finding the best possible compromise. Changing one characteristic will also alter the others in some manner. Safety is the number one priority, but developers also try to fine-tune the other characteristics for the best possible result.
“Products for different markets emphasize different features. The CE winter tires are quieter than summer ones. Although Nordic winter tires tend to be the quietest tires because of even thicker tread and softer tread compound than CE winter tires have. The tire’s interior noise characteristics are emphasized when the car is commonly used at speeds of 50–100 km/h”, says Head of R&D Olli Seppälä.
Even wear reduces tire noise
As the tire change season is ahead of us, drivers should note that changing the tires makes us sensitive to noise. Old tires also have low tread depth, which creates a different soundscape than new tires with their strong tread patterns.
Drivers can affect tire noise to some extent. First, you should make sure that your car and tires are fine. For example, if your suspension geometry is not within the manufacturer’s specifications, resulting in incorrect steering angles, the tires will wear down unevenly and generate additional noise. Even if your wheels are properly aligned, you should rotate your tires in order for them to wear down as evenly as possible.
Adjusting the inflation pressure can also affect tire noise. You can experiment with varying the pressure level. Hannu Onnela also has a tip for the road: “If you see two ruts on the road, try driving parallel to them for a more comfortable sound experience”.