Imagine driving along the highway when you reach a section of road that hasn't been repaired in years. Suddenly, you go from gliding smoothly to feeling and hearing every bump in the road. While there's no way to control what state the roads are in, your tires have a major influence on ride noise and comfort. Since your tires are the only points of contact between your car and the road, your choice of tires can affect how smooth or harsh and how quiet or loud your ride is.
All tires produce some level of noise during driving: the tread elements coming in and out of contact with the road, the tread compressing and rebounding, and air flowing through the tread pattern as the tire rolls. Tires may also vibrate from the engine, uneven road surfaces, or even very strong winds. Any vibrations in the tire echo in the inflated tire's cavity, which acts like a drum and amplifies the vibrations, usually noticeable as a whining or humming noise.
Pattern noise varies depending on the tread pattern's pitch sequence, or the sizes and shapes of the tread blocks. If all the tread blocks are the same size and shape, then every block makes the same noise as it meets the road, which makes the tire noisier overall. To remedy this, most passenger tires are tuned with variable pitch sequences, or varying block sizes and shapes. This alters the pattern noises that different blocks produce so that the noises balance each other out, keeping the overall level of ride noise at a minimum. Some high-end tires also incorporate a layer of sound-absorbent foam that dampens acoustics in the tire cavity.
Highway tires generally ride quieter than all-terrain or offroad tires. "Rib" tread patterns form a smoother contact patch than "block" tread patterns, and their low void ratios don't allow as much airflow in the tread. Conversely, mud-terrain tires to be noisier on paved roads because their tall, aggressive treads have a rougher contact surface, and the larger voids between tread blocks allow more air to flow through the tread. Load weight also affects pattern noise: the more weight a tire is carrying, the harder the tread presses against the pavement and the noisier the tire is.
Tire sidewall ratio can affect how your car rides on various road surfaces. Taller sidewalls are more flexible, so high-profile tires are better at cushioning shocks and vibrations from any unevenness in the road, making your ride softer and more comfortable. That said, increased sidewall flexibility also softens handling and cornering forces, which slightly interferes with driver input feedback and dampens handling precision.
Performance-oriented tires tend to have lower profile ratios because their shorter, stiffer sidewalls transmit steering input from driver to road very firmly, which makes handling sharper and more responsive. However, this also means the sidewalls provide the driver with very little cushioning to absorb shocks or vibrations, causing a grittier, louder ride.
Older cars depended more on the tires' sidewalls to cushion bumps, dips, and other road irregularities. Modern cars generally offer a smoother, softer ride because the suspension components play a greater role in absorbing shocks and vibrations, though tire profile ratio can still affect ride quality. Additionally, the weight of the tires and wheels can affect how effective your suspensions are.
Your car's ability to absorb shocks and vibrations depends on its sprung-to-unsprung weight ratio. When driving over bumps or dips in the road, your car's unsprung weight—wheels, tires, axles, brakes, and other components not supported by the suspensions—tries to bounce up and down. Suspension components use the sprung weight—the body, engine, transmission, chassis, passengers, and cargo—to counteract the force of its its unsprung weight. This shields the sprung weight from the shock of impact while holding down the wheels and tires on the road.
Increasing your car's unsprung weight causes the wheels and tires to bounce up and down harder. The suspensions can't absorb as much of the impact, so more bouncing gets transmitted to the driver and other passengers. The heavier your wheels or tires are, the harder it is for your car's suspensions to absorb shocks and vibrations, and the harsher your ride is. This also puts more stress on the suspensions, causing them to wear out faster.
Fitting your car with plus-size wheels and tires can improve handling, but could also impact ride comfort. Since the overall tire diameter needs to stay the same, a larger wheel diameter also means shorter tire sidewalls. This means the tires provide less cushioning against impacts and vibrations. Additionally, larger wheels are heavier and contribute more unsprung weight. Taller wheels also tend to be wider and thus need wider, heavier tires, which further reduces profile ratio and adds to unsprung weight. Usually, plus-sizing wheels by 1 inch won't cause too much of an issue, but going beyond 1 inch could significantly degrade ride quality.
Ride quality tends to degrade at higher speeds. The faster you drive, the more agressively the tread elements hit the road and the faster air rushes through the tread, causing louder pattern noises. The tires also have more kinetic energy when rolling over bumps or dips, making impacts harder. At lower speeds, your tires are quieter and ride more softly, making it easier for the suspensions or sidewalls to absorb shocks and vibrations.
Ride quality issues could also be caused by uneven treadwear. Uneven wear gives the tread a rougher surface that contacts the road more aggressively and noisily. If you're experiencing an unusually noisty ride or vibrations in the steering wheel, it's best to inspect your tires as soon as possible. Uneven treadwear is often a sign of tire maintenance issues that not only affect ride quality, but could put the tires at risk of failing.
Your tires could be in need of rotation, out-of-balance, or experiencing alignment issues. Tire balancing and correct wheel alignment are necessary to ensure that the tires come in contact with the road properly so that the treads wear uniformly all around. Tire rotations are also important in making sure that all four tires wear at the same rate and provide the same levels of ride quality. These steps ensure that each tire's tread forms a smoother surface as it wears, reducing pattern noise and improving ride comfort.
Squeaking or squealing tires may be a sign of underinflated tires, which are more susceptible to block squirm. Overinflated tires can cause a harsh, gritty ride, as their sidewalls are stiffer and have very little cushioning to absorb shocks. They are also more easily damaged by road impacts. Always check that your tires are inflated correctly, as underinflation or overinflation can cause tires to fail prematurely.