Off-road enthusiasts make all kinds of modifications to their vehicles to improve performance on the trail. Some of the more common modifications owners of off-road vehicles use include lift kits, suspension modifications, and oversized tires designed for rough terrain.
However, just because these modifications are commercially available, doesn't necessarily mean they're street legal. Every state has laws that impose limits on how far vehicle owners can go with off-road modifications, at least for vehicles that are driven on public roadways. Vehicle owners also need to make sure they don't strip off safety equipment that's required on all vehicles.
So before you invest in new tires or a lift kit, here are some basic rules regarding what is and is not allowed in most states.
All states have limits on the height of a vehicle. These limits may apply to the height from the ground, the overall height, or the materials used to lift the vehicle.
To clarify, a vehicle "lift" refers to any modification of the suspension or chassis to elevate the vehicle. Generally, vehicle lifts are either:
Basically, a suspension lift is achieved by extending the suspension of the vehicle. With a body lift, on the other hand, blocks are placed between the frame and the vehicle body.
Some states have specific laws regarding how a vehicle can be lawfully lifted. Generally, the laws aim to prevent unsafe modifications to a vehicle's suspension that could result in a dangerous equipment malfunction on the highway.
Lift kits are prepackaged assemblies that include all the necessary parts and pieces needed to lift or modify your suspension. Generally, lift kits are specially designed for the owner's vehicle for both durability and safety.
In some states, like California and Michigan, owners are only permitted to modify their suspension by the use of a manufacturer lift kit or by a professional mechanic.
Most suspension modifications use longer struts, springs, and leaves to increase the height and shock absorption capabilities of the vehicle. As a cheaper alternative, owners can install "spacers" between the spring and the axle to increase the height of the vehicle. The use of spacers does not improve the suspension performance and—if the spacers are tall enough—can actually compromise the stability and durability of the suspension assembly.
Some states have specific rules for body lifts. For example, Michigan prohibits lift blocks on the front of the vehicle and limits lift blocks to only four inches on the rear axle.
Even in states like Alabama with no specific laws governing suspension modifications, the lift upgrade must still comply with standard vehicle inspection laws. To ensure safety and create some uniformity between states, every state has laws regarding vehicle equipment and size limitations.
Overall height limits. Every state has a limit on the overall height of a vehicle. Obviously, a thirty-foot monster truck can't be operated on public roads that have bridges, underpasses, and overhead traffic lights. Most states, like Maryland and California, set this limit at 13 feet, six inches.
Bumper and light height limits. Most states also limit the distance between the vehicle body and the ground. Generally, these types of limits are measured from the vehicle's bumper or headlights to the pavement. For example, Michigan prohibits any lift where the frame is more than 12 inches from the ground or the bumper more than 22 inches from the ground. And, in Montana, a tail lamp can't be more than 72 inches from the ground.
In addition to lifts, off-road enthusiasts often use specialized tires to improve vehicle performance. But to be street legal, vehicle tires must meet certain standards.
Tires must be properly made and safe for use. Fortunately, federal law regulates how tires are made and manufactured. All tires sold in the United States will have a DOT certification on the sidewall. However, if the sidewall indicates "not for highway use" or "off-road only," the tire cannot be used on public roads.
Generally, there aren't actual size limits for tires (although special rules may apply for tires wider than 14 inches). Instead, most states require that tires fit properly within the wheel well.
If a tire is too tall, the vehicle may need to be lifted in order for the tire to fit under the wheel well. If the tire is too wide, the owner may need to install fender flares to extend out and cover the exposed tire.
Some states, like Alabama, don't have limits on exposed tires.
With aftermarket tires, a vehicle must still fit within the overall size limits for a vehicle.
Regardless of the specific tire laws, an oversized tire generally cannot make the vehicle more than 14 feet tall.
Likewise, a wide tire cannot make the vehicle exceed the standard vehicle width limit. Generally, vehicles are not permitted to be more than 8.5 feet wide.
States also have limits on the amount of tread a tire can have. Some off-road tires have small metal studs in the rubber to increase traction on dirt, ice, and snow.
Most states, like Kansas, prohibit the use of studded tires on highways. But some northern states with heavy snowfall (like Wyoming) permit them during the winter months.