My first new vehicle was a 1994 Toyota T-100 SR5 four-wheel-drive (4WD) with 31x10.50R15 tires. I always wanted a pickup and loved every mile I put on that truck. A few years later, my son was born, so I had to say goodbye to the T-100 because it was a standard cab with no place for a car seat. It’s still one of my first real grown-up decisions.
Fast-forward 30 years later and I’m back in a pickup truck after recently purchasing a 2019 Chevrolet Silverado. It’s a crew cab so there’s room in the back seat for the boy and it came with the factory two-inch lift. I had some steps added because I’m not a fan of running boards or jumping into and out of the cab.
In all honesty, my Silverado is a glorified grocery-getter that’s loaded, loud and fast. Suburban Baltimore is not exactly the perfect setting for a four-wheel-drive off-road pickup truck, but I did get to have a little fun after a recent snowstorm that left about five inches of the fluffy white stuff on the ground.
The original equipment (OE) tire on my Chevy is a 275/60R20 with a 114 load index. That size is 32.99 inches in diameter, according to the Tire and Rim Association (TRA), and mounted on a 20 x 8.0-inch rim. At 35 psi, the tire can support 2,601 pounds, which is the recommended inflation pressure for the rear tires. The recommended inflation pressure for the front tires is 32 psi, which can support 2,502 pounds. According to the placard found on the truck’s door jamb, the maximum weight of the occupants and cargo is 1,685 pounds.
I seriously doubt I will ever come close to that.
If I wanted to install a larger tire on the same rims, then the maximum diameter of the new tire would be 3% of 32.99, which is 33.98 inches. Again, according to TRA, the 285/60R20 at 33.46 inches and the 295/60R20 at 33.94 inches are both within 3% of the OE diameter and the 8.0-inch rim width is acceptable for both tires.
The 285 and 295 have a load index of 116, which is greater than the 275. At the placard pressures of 32 psi and 35 psi, both tires carry more weight than the original size, so there is no need to adjust the tire pressure monitoring system (TPMS). From the legal perspective, it would appear that every box would be checked if I opted for larger tires in those sizes on the same rims.
The truck’s OE tires happen to be passenger tires. However, there are more light truck-metric tires available in larger sizes, which changes the rules. The U.S. Tire Manufacturers Association (USTMA) publishes a document called “Care and Service of Passenger and Light Truck Tires,” which is the primary authority for replacing passenger tires with light truck tires.
According to the USTMA, the passenger tire load-carrying capacity must be reduced by dividing by 1.10 when replacing a passenger tire with a light truck tire. The USTMA also points out that a higher inflation pressure is often required — more on that later!
When you divide 2,601 pounds by 1.10 you get 2,365 pounds for the rear, while 2,502 divided by 1.10 is 2,275 pounds for the front. The TRA Yearbook shows that the LT285/60R20 is a Load Range E tire, with a maximum pressure of 80 psi and maximum load of 3,640 pounds in a single application.
At 45 psi in a single application, the LT285/60R20 LRE will carry 2,410 pounds, so the new rear inflation pressure would be 45 psi. At 40 psi, the LT285/60R20 only carries 2,220 pounds, so the new inflation pressures for the front and rear tires would be 45 psi.
The LT295/60R20 in a single application carries 2,530 pounds at 45 psi and 2,330 pounds at 40 psi, so the inflation pressures would be 40 psi in the front and 45 psi in the rear. In order for the TPMS to operate as designed, the underinflation thresholds would need be reprogrammed to reflect the higher inflation pressures.
The USTMA warns drivers that higher inflation pressures when replacing passenger tires with light truck tires may exceed the capacity of the rim, so the manufacturer should always be consulted. According to TRA, the minimum rim width for the LT285/60R20 and the LT295/60R20 is 8.5 inches, so I would need to purchase new rims if I opted for the larger sizes in a light truck tire as opposed to the passenger tires currently on the truck.
I have no plans of changing my truck’s tire size, so it isn’t a concern for me. But it could be a concern for the tire dealer that would potentially install larger light truck tires. While the 3% rule for diameter change is within industry-approved limits and the TPMS underinflation threshold can likely be reprogrammed to reflect the higher inflation pressures, the rim width would become an issue if the larger light truck tires were installed on my truck’s original rims.
When the rim is too narrow, the tire footprint is changed and more wear should be expected in the middle of the tread. In a courtroom situation, a plaintiff’s expert could argue that the change in footprint resulted in less tread to road contact, so any loss of control would be at least partially attributed to the fact that the original rims were too narrow for the light truck tires, according to the TRA Yearbook.
When I inquired, a local custom truck shop recommended that I step up the 275/65R20 to fill the wheel well better. They thought the OE tires are too small with the two-inch factory lift, so the 65 series tires, in their opinion, are the way to go. However, at 34.09 inches, the passenger and light truck tire versions of the 275/65R20 are just outside the industry-approved 3% limit, so neither are recommended. While you’re only talking about a difference in diameter of just 0.11 inches, it’s over 3%. I was involved in a legal case years ago with a similar difference in diameter outside the correct 3% limit and it was enough to file the lawsuit and extract a settlement.
In the SUV, pickup truck and Jeep world, many vehicle owners believe that bigger is better. The safest approach is to follow the 3% rule for diameter and make sure the rim width is approved for the tire size. The primary risk of a lifted vehicle is the increased potential for a roll-over due to its higher center of gravity. Tests have shown that when the tire diameter changed by more than 3%, there is a greater risk of losing control of the vehicle. The USTMA’s guidance on changing diameter when plus-sizing is this: “Check to be sure that the overall diameter of all four tires is within the accepted tolerance of the vehicle manufacturer.”
The Tire Industry Association (TIA) also continues to publish the 3% limit because that was the last published guideline.
But this is where it starts to get tricky. In my opinion, there’s a difference between an installer who makes the switch to a larger tire size by changing the fitment and the installer who relies on someone else’s fitment decision when selling replacement tires.
It’s a legal standard-of-care quagmire because I believe there can be a different standard for a company that installs a lift kit with larger tires and another company that is asked to provide replacement tires for a vehicle that has already been customized by someone else. When you’re the expert advising the customer on what tire and wheel package works best with which lift kit, then it’s reasonable to expect that manufacturer and/or industry guidelines are followed during fitment and installation.
On the other hand, when you’re a tire dealer who’s been asked to install replacement tires on a vehicle that has already been outfitted with a lift kit and/or custom tires and wheels, it’s not reasonable for the customer to expect you to reverse-engineer everything to determine if something like the 3% guideline was followed or not.
I would say the same thing about any replacement tire situation if the size is different than the placard, with a few caveats. One caveat is that the replacement tire cannot have a load index that is less than what is listed on the placard. Number two, the speed rating should be equal to or greater than the OE fitment. I also have some concerns about rim width if the tire is excessively too wide for the approved rims. But as long as the load capacity and speed rating are in line with the OE fitment, it should be acceptable to replace the tires on the vehicle.
The guidelines for plus-sizing are pretty clear. As long as the diameter doesn’t change by more than 3% and the load index and speed rating are equal to or greater than the OE tire, there isn’t much to worry about. If the diameter is over 3% with the load index and speed rating equal to or greater than, then there will be some concern regarding vehicle stability. How much concern depends on how much greater. On the other hand, if the replacement tire diameter is over 3% with a load index and/or speed rating that is less than the OE fitment, the risk is going to increase significantly.
Speedometer accuracy also has a role in plus-size tires. Vehicle speed is determined by the tire circumference since there is a set distance that a tire will travel in one revolution. If the tire has a larger circumference, then it will travel further in one revolution and cause the speedometer to read under the actual vehicle speed. Even with a 3% increase in diameter, the difference in circumference would result in the vehicle traveling at over 63 mph even with the speedometer reads 60 mph.
Again, the bigger the difference in diameter/circumference, the bigger the difference in speedometer accuracy. Within the 3% guideline, the difference is negligible, but the inaccuracy of tires outside the limit should be a cause for concern, so speedometer recalibration should be performed or at least recommended.
Another factor that must be considered in the lift kit, monster truck market is the amount of lift that is allowed and the height of the bumper. According to RealTruck, some states have strict restrictions, like Georgia, which limits suspension lifts to two inches, while the maximum frame and bumper height are determined by the gross vehicle weight rating (GVWR) in states like Florida, Hawaii, Idaho, Illinois, Maine, Maryland, Michigan, Missouri, Nevada, Ohio, Pennsylvania, Tennessee, Utah, Virginia and Washington. Alabama, Arizona, Arkansas, Iowa, Kansas, Kentucky, Louisiana, Mississippi, Montana, Nebraska, New Mexico, North Carolina, Oklahoma, Oregon, South Carolina, South Dakota, Texas, Vermont and Wyoming have no restrictions for body lifts or suspension systems.
Any business making the lift kit fitment decision and installation must abide by state laws for the amount of allowable lift and bumper height. If the driver gets a citation, then the installer may have to make some adjustments. If the driver is involved in an accident and the illegal vehicle/bumper height contributed to the injuries or fatalities of another driver or vehicle occupants, then the installer can be sure that they will be named in any future litigation.
There is an implied warranty that accompanies every product and service that cannot be denied. It’s reasonable for a customer to expect that the lift kit installer followed the manufacturer guidelines for installation and the vehicle is compliant with state and local laws regarding vehicle/bumper height.
The newest monkey wrench in this discussion is the next generation of advanced driver-assistance systems (ADAS), and the sensors and cameras that help detect obstacles and correct driver error. Forward collision warning, automatic emergency braking, adaptive cruise control and lane departure warning/assistance are just a few examples of ADAS in late-model passenger vehicles.
ADAS is not new to the automotive market. Federal Motor Vehicle Safety Standard (FMVSS) 49 CFR 571.126 has required electronic stability control (ESC) on new passenger vehicles with a gross vehicle weight rating of 10,000 pounds or less in the U.S. since the 2012 model year. Anti-lock braking systems (ABS) have also been required in the U.S. since 2011, per FMVSS 126, and both technologies are under the ADAS umbrella. As it stands today, they are the only two types of ADAS on new vehicles that are required by federal law. Therefore, they fall under the “make inoperative provision” in 49 U.S.C. 30122(b), which prohibits a motor vehicle repair business from knowingly disabling a motor vehicle safety system that is required by an FMVSS. The most well-known 30122(b) violation in the tire industry is related to the intentional disablement of the TPMS, but it applies to all safety systems.
If any vehicle modifications cause a required safety system to become inoperative, then a violation of 30122(b) exists. Any tire dealership or auto repair business that knowingly makes a required motor vehicle safety system inoperative is playing with fire. In the event of an accident, the liability will fall squarely on the shoulders of the business that disabled the system or made it inoperative. One can make the case that ineffective and inoperative are one in the same.
Modifications that make ESC or ABS less effective or accurate could essentially make the system inoperative because it is not functioning as designed within the performance requirements outlined in FMVSS 126. There’s no gray area when it comes to 30122(b). If the motor vehicle safety system is required by an FMVSS and the intentional actions of the repair business make it inoperative, a violation is easy to prove in a court of law.
When the Infrastructure Investment and Jobs Act was passed in 2021, Division B was called the Surface Transportation Investment Act of 2021. This portion of the legislation included a number of safety improvements for passenger vehicles that include ADAS. One particular area that got a lot of attention was automatic emergency braking (AEB). The National Highway Traffic Safety Administration (NHTSA) issued FMVSS 127 to set the performance and testing standards for AEB systems on all passenger and multipurpose passenger vehicles with a GVWR of 10,000 pounds or less. After Sept. 1, 2029, all passenger vehicles must have a compliant AEB, but small-volume manufacturers and final-stage manufacturers have an extra year to become compliant with a Sept. 1, 2030, deadline.
AEB systems use sensors to detect when the distance between the vehicle and another vehicle or pedestrian is insufficient and apply the brakes if the driver fails to act. NHTSA projects that this technology will save 362 lives and mitigate 24,321 non-fatal injuries each year. Pedestrian AEB performance must detect a pedestrian during daylight and darker conditions at night. FMVSS 127 requires all passenger vehicles to stop and avoid contact with a vehicle in front up to 62 mph and apply the brakes automatically up to 90 mph when a collision is imminent and up to 45 mph when a pedestrian is detected.
The Specialty Equipment and Marketing Association (SEMA) has been focused on vehicle modifications and ADAS for years. In May 2022, SEMA published an article that included a case study on lifted pickups. According to SEMA, if the vehicle has a radar system, it must be set at a specific level, typically +/- 0.1-0.3 degrees or to bubble level. When a two-inch lift kit is installed on a truck, the sensor could be off by 0.5 degrees. A sensor that’s off by even one degree limits the effective range of the radar by 10% and a two-degree misalignment limits it further by 25%. If the sensor is off by three degrees, then the misalignment limits the effective range by 50%.
If onboard cameras are used as part of the ADAS, they are also affected by lifting or lowering the vehicle. In order for an onboard camera to estimate the distance between the vehicle and an object, the height and pitch angle must be precise. The camera uses the horizon line to calculate the distance so any changes to the angle of the camera are going to affect the ability to read the horizon line accurately. SEMA indicated that “a camera pitch error of only two degrees can result in an inaccurate reading of up to 16 meters. A pitch error of minus-two degrees can lead to (a) wrong reading of up to 90 meters — length of a football field.”
The passage of FMVSS 127 creates another gray area for the vehicle customizer. Prior to the new safety standard, any inoperative claims would be associated with the standard of care. Now that FMVSS 127 is the law, that changes. Does it mean that 30122(b) now applies to AEB or does the "knowingly make inoperative" provision only apply after Sept. 1, 2029, when all vehicles are covered? I don’t have an answer to that question, but I’m fairly confident when I say the best practice is to make sure a lifted or lowered vehicle with an AEB is recalibrated to ensure it is compliant with federal law.
That being said, there will be no questions regarding AEB on the 2030 model year moving forward when it’s mandatory on all new passenger vehicles sold in the U.S.
But it’s not just lifting or lowering the vehicle that can have a negative effect on ADAS performance. Body modifications and custom bumpers may block or obscure a sensor. Manufacturers have specific areas where sensors can and cannot be relocated. In some cases, relocation may create problems for proper ADAS functioning, while in others it simply will not work as designed.
As if all of this was not complicated enough, it’s important to remember that sensors vary by manufacturer — sometimes in the same model year — and there are always software updates lurking to drive technicians crazy when everything is done by the book, but the system still won’t recalibrate.
The calibration process itself has its own set of rules and conditions. One is that the floor must be almost perfectly level: +/- 7 millimeters according to SEMA. It’s also important to have enough space in the shop to properly position a target to calibrate the ADAS. If the target is too close, the ADAS can be “spoofed,” which results in inaccurate readings.
The SEMA Garage has an ADAS Center that continues to study what happens to these safety systems when a vehicle is modified. SEMA has taken the lead in testing and training to prepare aftermarket vehicle customizers for the current and future changes in technology so the industry has the answers and guidance needed to ensure vehicles are compliant and the motoring public is protected.
Accident and injury lawyers are well aware of the risks associated with lifted vehicles. One firm points out that lifted SUVs and light trucks are more prone to rollover and “they have farther to fall than a normal vehicle.” The raised vehicle height or higher bumper “would destroy some lower-profiled vehicles at worst and cause significant damage at best.” They go on to say that the raised height increases the number of blind spots and height of the headlights can be problematic for the driver and other motorists.
We live in a very litigious society, so someone has to be at fault in the event of an accident. There’s always something that could have been done to prevent it from happening or some warning that could have been given that would have made the injured party aware of the risks. Liability waivers are used to shift the responsibility for any injuries from the company to the customer. Another law firm provides five reasons why liability waivers may not hold up in court:
- Enforceability. Every state and local jurisdiction has different enforceability requirements for liability waivers;
- Types of liability. Waivers are more effective in cases of simple negligence or ordinary risks, but situations involving gross negligence or intentional misconduct can invalidate a waiver depending on the jurisdiction;
- Clear and unambiguous language. Waivers should be clearly written, using plain language that is easy to understand;
- Voluntary and informed consent. In order for the waiver to be enforceable, the party signing it must do so voluntarily with a full understanding of what it implies;
- Professional advice and risk awareness. Adequate warnings, proper employee training and following the standard of care improves waiver enforceability.
Do you see what I did there? The legal firm was focused on why waivers were not enforceable and I used it to provide a nice little checklist what to look for in a quality liability waiver. I’m not a lawyer, but I’ve been involved in enough civil litigation to know that failure to warn is easy to prove when the customer is not warned about any potential risks related to a product or service.
Every vehicle modification that changes the tire size or vehicle height should be accompanied by a clear and strong liability waiver that includes a customer signature stating they have received the waiver and understand the risks they assume as a result of their decisions.
I also strongly believe it should be drafted by an attorney that understands the nature of the products and services, so they can create defendable language that protects your business. This isn’t something you draw up after work for the above reasons.
Customers who want larger tire and wheel packages and/or lifted SUVs and pickup trucks must understand that the decisions they make are going to affect how the vehicle handles. In a perfect world, the customer who wants a four-inch lift with tires that are +10% of the OE diameter should assume all of the liability in the event of an accident, if the installer followed the standard of care for tire replacement outside the change in diameter. If the lift kit was installed according to the manufacturer specifications by a trained technician and the ADAS was recalibrated in the same manner, then there shouldn’t be any liability if the customer understands that despite the steps taken to ensure proper operation, the vehicle has been altered at their direction and therefore handles differently. Likewise, if the tires are outside the +3% limit but the load index and speed rating requirements have been satisfied, that decision by the customer is going to affect braking and handling so the customer should assume the liability.
Every product and service creates risk for a tire retailer or vehicle customizer. The level of risk depends on a wide variety of factors that are both defined and undefined. Customers who want the larger tires and lift kits on their pickup trucks and SUVs have the right to do whatever they want, as long as the modifications are compliant with state and local laws regarding vehicle and bumper height.
As an expert in civil litigation, it’s frustrating to see businesses held liable for providing the product or service requested by a customer who accepts zero responsibility. As long as the installation of modifications are consistent with industry best practices and guidelines, there shouldn’t be additional risk when customers want tires that are over the 3% limit if they sign a waiver and all other criteria for plus-sizing tires are met.
As we enter a new era of vehicle safety technology with the current and future forms of ADAS, the automotive aftermarket must adapt. SEMA has taken positive steps to conduct the testing and research that the industry needs to gain a better understanding of how the systems react to vehicle changes so steps can be taken to ensure federally mandated safety systems continue operating as designed after modifications have been made.
For the more than 90% of retailers that stay within the industry guidelines and the TIA recommended specification of +/-3% when changing tire diameter, nothing should change. I say “should” because 3% is still 3% and the difference will have an effect. It’s uncharted territory for technology like AEB because it’s still on a pretty small number of vehicles compared to the total in operation.
Without a doubt, the best and safest practice is to follow the vehicle placard when replacing tires. If the size, load index and speed rating are a match to the OE tire, there are no risks related to any form of ADAS. The vehicle should perform as designed. When adjustments are made to the tire size that ultimately changes the diameter, there is additional risk that one or more types of ADAS will not function properly.
If that ADAS is ESC, ABS or AEB, then a completely different level of risk must be assumed. The best the installer can do is follow all of the published guidelines for whatever modifications are made to the vehicle.
As far as waivers are concerned, I believe that some protection is better than none so a discussion with the insurance carrier and corporate attorney is a great place to get started. There is nothing you can do to prevent a lawsuit in the event of an accident. If something goes horribly wrong, civil litigation will follow because someone has to be at fault. I’m not a fan of the system, but I have some experience related to how it works. There are a lot of boxes that need to be checked to safely lift a vehicle and/or install larger tires and rims. The introduction of ADAS, specifically AEB, is going to create more boxes that are not easy or inexpensive to check.
I hope a quality liability waiver offers additional protection, but it depends on the state and the circumstances surrounding the accident should one occur. In the end, there will be a list of actions that the installer followed to ensure safe operation of the vehicle while the plaintiff will produce a list of things that were not followed that led to unsafe operation.
The standard of care for lifting pickup trucks is shifting when it applies to technology like ADAS. Staying in that business is going to require a higher level of commitment, equipment, and technician training. Each tire dealer will have to decide how much risk they are willing to assume when a customer wants a four-inch lift with monster mud tires on a 2030 Jeep.
AEB is a game-changer because it opens up new doors of liability that the industry has never experienced. Right now, the questions just create more questions. Hopefully, there will be some answers in the near future, but they may not be the most popular in the SUV and pickup customization industry.
About the Author
Kevin Rohlwing
Kevin Rohlwing is chief technical officer of the Tire Industry Association. He can be reached at [email protected].