In Search of Quiet Tires

Everybody wants a quiet ride, but what is it about a tire that makes it quiet? Tires that boast a quiet ride almost always offer similar features: smooth airflow, good insulation, and a build that lowers vibration.

You probably think that tires are all built pretty much the same way, so you may not even consider that things like airflow and insulation would be that different. As for vibration, that’s basically just friction. How can a tire not have that? However, each of these factors can differ from tire to tire, and they’re controlled during engineering and manufacturing process to determine just how quiet each tire will be.

According to tire industry studies, tires have gotten a lot quieter in general (at least since the 1980s). Even so, some are going to be quieter than others.

Air Noise

If you think about it, a car traveling at 65mp on the highway is going to generate some wind noise, especially if you’re driving into the wind. How much noise can depend on its shape, and on top of that, the tread spinning around the outside of the tire is going to generate noise too. In fact, that tread is moving at an even higher rate when it cuts into that wind. So how can you control that?

One way to lessen the wind noise is to make rain channels straight rather than staggered. Narrower grooves also generate less wind resistance.

To see what I’m talking about, compare a regular highway touring tire with an all-terrain tire. The touring tire probably has more straight channels, while the all-terrain tire, which isn’t as concerned about noise, is more likely to have zigzag channels and even some overlapping tread blocks. The blocks on the touring tire are also going to be smaller than the ones on the all-terrain tire, and the voids (or grooves) between them are going to be narrower as well. All of these seemingly tiny changes serve to reduce the tire’s wind resistance.

Some manufacturers also mold shapes into the bottom of grooves themselves to further lessen turbulence for an even quieter tire.

Road Noise

The act of the tire rolling along, rubber against the road surface, is what generates the most noise. The amount of rubber and how hard it is can greatly affect how much noise.

• Narrow tires are quieter than wider tires. Less rubber on the road means less friction and vibration.
• Tires with silica in the tread compound are more flexible, even in the cold, and this makes them quieter. The harder a tire is, the more noise it’s going to generate. High performance or summer tires made for maximum warm-weather traction,especially at speed or around curves, is likely going to generate more vibration, too.
• Smaller tread blocks and narrower voids produce less vibration and lower noise. Tires with bigger blocks, like all-terrain tires and (especially) mud tires, are going to be noisier. Those tires also have wider grooves, as mentioned above, which just adds to the noise..
• This may seem obvious, but winter tires without studs are going to be quieter than studded tires, even if they’re otherwise identical. But let’s face it, if you have studded tires you’re probably more worried about traction than noise.

There is, of course, other types of road noise. For example, decades ago winter tires used to be known for their roar. Now it’s commercial truck tires. Whether they’re on the highway or going through a town, those tires scream. This is usually because commercial truck tires have very little variation in their tread: every block and rib is the same shape, the channels are the same width, grooves are the same size. When all the elements are pretty much the same like that, it creates more noise.

Today, engineers use computer programs to design their treads. This allows subtle size and shape variations between all the tread elements that you may not even be able to see. These different sized tread elements produce different pitches of sound. This is what tire companies refer to as a “variable pitch” tread. These variations, while harmonic, are still noise, but it’s less grating on the ear and therefore easier to ignore.

Internal Noise

Tires are flexible rubber containers filled with compressed gas (usually air but sometimes nitrogen). So, just like other rubber containers filled with compressed gas (like a ball), it’s going to make a “boing” or similar sound when it hits a surface. That’s basically the soundwaves bouncing around inside the ball. Except tires do that many more times per second (and per minute) than a bouncing ball does. The faster you drive, the more this type of noise is created. Same if the road quality decreases. This sound carries into the cabin through the air and also through the vehicle’s structure.

Tires marketed as quiet are engineered to reduce that sound, but how do they do it? Well a good example is either the Conti Silent or the Michelin Acoustic tires. Both models have a foam layer inside the tire, just beneath the tread area (not on the sidewalls), and this reduces booming when the tires bounce. Michelin says the technology reduces noise by 20 percent.

Proper Maintenance Helps

As with most things, proper maintenance is important. Regardless of the tires you buy, if they’re maintained properly you can reduce the noise. So what does that mean? For one thing, make sure to check your alignment. Misalignment can cause uneven wear patterns and that will just increase the road noise. Another good tip is to keep the wheels balanced. If it’s not balanced properly, a tire will bounce more, increasing that “boing” sound. Lastly, make sure your tires are properly inflated and rotated. This ensures that the tread meets the road surface the way it was designed to and that the wear remains even. It’s recommended you rotate them every 6,000 miles (or twice a year, whichever comes first) to promote even wear all around.