Tread Void Ratio for Highway Tires: What Is Ideal

What is tread void ratio?

Tread void ratio describes how much of the tread surface is open space versus solid rubber. In regulatory terms, a groove is the space between two adjacent tread ribs, and the tread is the portion that contacts the road, according to 49 CFR 571.109. The void ratio is the percentage of the footprint occupied by those grooves, sipes, and channels. A low void ratio means a more solid, continuous rubber surface. A high void ratio means a more open, blocky pattern. To see how different tread patterns affect performance, check out our overview of tread pattern types.

Manufacturers don't always publish an exact void ratio number, but you can estimate it by looking at the tread pattern. Highway tires tend to have narrow, shallow grooves and large continuous ribs. Off-road tires have wide, deep voids and independent lugs. For pavement, the goal is to keep the void ratio low enough to maximize contact while still providing channels for water evacuation.

Why a low void ratio works on the highway

On dry pavement, a low void ratio maximizes the rubber-to-road contact, which supports braking and cornering forces. The continuous rubber also spreads load evenly, which can help treadwear and high-speed stability. On wet pavement, grooves are needed to evacuate water and resist hydroplaning; learn more about how grooves affect hydroplaning. Highway tires use moderately narrow and straight grooves that keep the void ratio low while still channeling water effectively. Deep, wide grooves like those on off-road tires increase the void ratio and reduce the contact patch, which hurts wet grip.

The trade-off is real: a higher void ratio helps in mud and snow, but on asphalt it means less rubber is actually touching the road. For most highway driving, a tire with a closed shoulder and a rib-type pattern is the safest and most predictable choice.

How all-terrain tires sacrifice wet highway grip

All-terrain tires trade highway manners for off-road capability. They have larger tread blocks, wider voids, and more aggressive shoulder lugs. Those features let the tire clean out mud and grab loose rocks, but they also reduce the rubber area on pavement. As a result, all-terrain tires often have longer braking distances on wet asphalt and less steering precision at highway speeds. They also tend to be noisier and to generate more heat at sustained speeds. For a detailed look at how tread patterns respond to weather, see our article on tread versus weather.

That doesn't mean all-terrain tires are unsafe on the highway; it means you should expect a performance compromise. If you spend most of your time on pavement and only hit gravel roads occasionally, a "highway-terrain" tire or a mild all-season with a moderate void ratio is often a better balance.

For a deeper comparison of tread patterns, see our guide on tread pattern types.

Tread pattern and void ratio

Tread pattern types directly affect void ratio. Rib-type patterns have continuous circumferential grooves and low void, making them ideal for highway use. Lug patterns have more void and are better for off-road. Symmetric and asymmetric treads also change how void is distributed across the contact patch. For highway commuting, look for a tire with a closed shoulder and narrow grooves.

You can also check the tire's UTQG ratings, but note that the UTQG system grades treadwear, traction, and temperature, not void ratio directly. Still, a tire with a traction grade of A or AA is designed to perform well on wet roads. For more, see our UTQG explanation.

Hydroplaning resistance depends on groove design as well. A low void ratio doesn't automatically mean poor water evacuation if the grooves are properly shaped and oriented. The key is that the channels must move water away from the contact patch efficiently. Learn how wet weather grip is influenced by tread design.

How to choose for highway use

For most passenger cars and SUVs that stay on pavement, an all-season or touring tire with a low void ratio is the right choice. These tires balance wet grip, wear, and comfort. For trucks used for towing on highways, a highway-terrain tire with a rib pattern is often best. If you occasionally drive on gravel or dirt but mostly on highway, consider a light-duty all-terrain with a moderate void ratio, but accept the tradeoff in wet braking and noise.

Use our guides to compare tire options in your size. Start with the best all-season tires guide for most commuters, or the best light-truck tires guide if you drive a pickup or SUV. For high-performance needs, a summer tire with a very low void ratio can maximize dry grip, but it sacrifices winter traction.

• Highway commuting: choose a ribbed all-season or touring tire with a low void ratio.
• Towing or hauling: highway-terrain light-truck tires offer a good balance of stability and wear.
• Occasional off-road: an all-terrain tire with a moderate void ratio is acceptable, but expect reduced wet-pavement grip.
• Performance driving: summer tires have very low void ratios for maximum dry grip, but they're not for cold weather.

What to pick for your use

Questions

Is a lower tread void ratio always better on pavement?

Yes, for dry and wet asphalt, a lower void ratio means more rubber in contact, which improves braking and cornering. The exception is standing water, where grooves are needed to prevent hydroplaning. Highway tires balance this with narrow, straight grooves that keep void low but still evacuate water. For more on how grooves affect safety, see tire grooves and hydroplaning.

How can I tell if a tire has a low void ratio?

Look at the tread pattern. Tires with continuous circumferential ribs and narrow, straight grooves have a low void ratio. Tires with widely spaced, large tread blocks and deep, wide channels have a high void ratio. Some manufacturers list approximate void percentages in their spec sheets, but it's not a standardized label.

Why do all-terrain tires feel less grippy on wet highways?

All-terrain tires have larger voids and more open tread blocks to shed mud and debris. That reduces the rubber contact patch on pavement, which hurts wet grip and increases stopping distance. The tread blocks also flex more, which reduces steering response and stability at highway speeds. Learn about the trade-offs in our all-terrain vs. highway guide.

Does tread void ratio affect tire noise?

Yes. Higher void ratios tend to produce more noise because air is pumped through the grooves as the tire rolls. Low-void, ribbed highway tires are typically quieter. If highway comfort is important, a low-void all-season or touring tire is often the better choice.