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The Final Word: NHTSA Clears the Air on TPMS Regs and Plus-Sizing Conundrum

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Knowledge and information. Both are more critical in today’s automotive industry than at any other time in history. Unfortunately, most of us lack the time to read every detail regarding the very products that give us our livelihood.

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It doesn’t help when government agencies, trade groups – even word-of-mouth – confuse and confound what should be cut-and-dried matters.

No issue has grabbed the attention of tire dealers and performance shops like tire pressure monitoring systems (TPMS) – most especially how the National Highway Traffic Safety Administration’s own rulemaking has created the ultimate conundrum:

Can you sell and install aftermarket wheels and tires on a customer’s vehicle, even if those products do not permit the vehicle’s factory-installed TPMS to function correctly, which is entirely counter to federal regulations prohibiting anyone from disabling vehicle safety systems?

Depending on whom you talk to, you could get all kinds of answers. Most of them, unfortunately, are wrong.

In most cases like this, the smart move is to err to the side of caution. Extreme caution usually keep you out of hot water, after all. The problem is, if the entire industry took that route, an entire segment of the replacement tire and wheel market – your livelihood – would cease to exist.

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Some folks trying to interpret FMVSS 138 (the TPMS regulations) would have you believe the only replacement tires and wheels you can legally sell would be the same size and construction as the OE units. No more plus sizing, no more performance market.

Others see it another way: Plus sizing is okay, provided the TPMS still functions with the larger tires and wheels. It is up to the tire dealer or performance shop to make sure the TPMS functions as intended. In practical terms, it would almost surely preclude sales of 20-inch or larger wheels and 35-series or lower aspect ratio tires; there is simply not enough sidewall there to get around valve-stem TPMS sensors.

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Still another faction sees it this way: Providing you do not intentionally disable the TPMS warning system, installing plus-sized tires and wheels is okay. The TPMS doesn’t have to continue functioning as intended after first tire replacement.

In fact, the heart of the confusion does not lie with FMVSS 138, but rather with an older federal regulation: 49 U.S.C. 30122(b), which read: “A manufacturer, distributor, dealer, or motor vehicle repair business may not knowingly make inoperative any part of a device or element of design installed on or in a motor vehicle or motor vehicle equipment in compliance with an applicable motor vehicle safety standard…unless the manufacturer, distributor, dealer, or repair business reasonably believes the vehicle or equipment will not be used when the device or element is inoperative.”

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In short, 49 U.S.C. 30122(b) means you as a tire dealer or performance shop cannot disable any vehicle system required by federal regulation. That means things like audible seat belt warning chimes or driver side airbags or, in this case, TPMS warning and malfunction lights. Notice the inclusion of the words “warning and malfunction lights.”

Here are NHTSA’s own words on the matter, taken directly from its FMVSS 138 final ruling issued in April 2005:

“We do not believe it is appropriate to permit disablement of the MIL (malfunction indicator lamp) when aftermarket tires and rims are installed on the vehicle that are not compatible with the continued proper functioning of the TPMS. In such cases, the TPMS MIL is performing its intended function. We believe that the MIL should continue to operate when tires and rims that are incompatible with the TPMS are mounted on the vehicle, not only to discourage such actions, but also to provide an ongoing reminder that the TPMS is unavailable to provide low tire pressure warnings.”

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Okay, so that’s not the most pro-aftermarket thing NHTSA will write, but you can see its point. TPMS in and of itself is not the safety system, the MIL that warns the driver of low inflation pressure or a system malfunction is the safety system.

Not convinced? Well, we contacted NHTSA directly. Here is the question as it was asked, and NHTSA’s verbatim response:

TR: In regards to installing aftermarket wheels and tires on a vehicle, the current mandate indicates that if the TPMS sensor cannot or does not work with the new replacement tires and/or wheels, it is still acceptable to install them, but neither the vehicle owner nor the retail dealer can disable the dashboard warning lamp. Is this, indeed, the case?

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NHTSA: “That is correct. After first retail sale of the vehicle, we do not believe that installing aftermarket tires and wheels necessarily makes the TPMS ‘inoperable.’ However, the MIL cannot be disabled. If the vehicle owner so desires, the vehicle could be taken to a dealer that has the replacement parts and tools necessary to repair and calibrate the TPMS system.”

TR: FMVSS 138 applies to an untitled vehicle. Is there going to be a mandate to apply those regulations beyond the first owner? If so, has there been a date set for compliance?

NHTSA: “We have no legal authority over individual use of a vehicle. Businesses installing aftermarket wheels and tires may not disable the malfunction indicator light and this prohibition is for the life of the vehicle. Individual states have legal authority to enact laws, and could require TPMS to function per FMVSS 138 even after modifications (such as installation of aftermarket tires and wheels) are performed by the private vehicle owner and an aftermarket business.”

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NHTSA’s response to our questions is, in fact, consistent with FMVSS 138 regulations that it drafted:

“…to require the TPMS-equipped vehicle to be certified with the tires originally installed on the vehicle at the time of initial vehicle sale. We emphasize that it would not be permissible for (auto) dealers to install tires on a new vehicle that would take it out of compliance with the TPMS standard, and to do so would violate the prohibition on manufacturing, selling, and importing non-complying motor vehicles and equipment in 49 U.S.C. 30112. If the consumer cannot expect to acquire a vehicle that meets all applicable safety standard at the time of first purchase, the purpose of Standard No. 138, and in fact all Federal motor vehicle safety standards, would be severely undermined. Furthermore, we expect that vehicle manufacturers, in light of their close relationship to their dealers, would provide sufficient recommendations to allow dealers to install alternate tires that permit the TPMS to function properly.”

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So, the bottom line here is:

• 49 U.S.C. 30122(b) does apply, but only to the TPMS low pressure/malfunction warning lamp.

• While NHTSA would prefer otherwise, sales and installation of aftermarket tires and wheels – and plus-sizing – is perfectly acceptable, providing your shop does not disable the TPMS MIL.

• Aftermarket tires are still not required to work with factory-installed TPMS.

• If you work with an auto dealer to sell and install wheels and tires on new, untitled vehicles, FMVSS 138 requires that the entire TPMS – sensors and MIL – function as if it were OE.

• If the vehicle owner, after buying replacement tires and wheels, still wants the full benefits of their TPMS, they can take the vehicle back to the auto dealer and have the TPMS reinstalled or reprogrammed to work with their new wheels and tires.

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• Beware of your state’s regulation activity as it may pass a law mandating that the entire TPMS – sensors and MIL – continue to function like OE even after the owner buys and installs aftermarket wheels and tires.

Other Questions

Since we had access to NHTSA – and had a bunch of other relevant issues you have brought to our attention – we asked a number of other questions. You might be interested in NHTSA’s answers.

TR: FMVSS 138 rule allows for the automakers to use a wide array of available systems. This has caused a great deal of confusion when trying to service TPMS sensors, which can lead to consumers having difficulty in getting routine service performed on their vehicles. Specifically, relearn procedures take as much as a year to get into the hands of the independent tire dealers and aftermarket performance shops, which forces the vehicle owner to take their vehicle to an auto dealer for TPMS service.

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If there were TPMS standardization and one common relearn procedure, this would be avoided. Considering the various types of TPMS and their wide variation in protocol, can NHTSA mandate that the manufacturers of these systems establish a ‘standards committee’ that will work to assure all manufacturers build to the same specs and use the same installation and relearn procedures and protocols?

NHTSA: “We issue a performance standard and leave the manufacturers to figure out how to comply with the requirements.”

TR: The current threshold to warn the driver of low air pressure is 25% below the automaker’s recommended inflation pressure. Will this percentage be revised?

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NHTSA: “The threshold will not change. We feel that 25% is a comfortable margin of safety and reflects a technology-neutral approach. We feel that a tighter tolerance will cause too many warnings and consumers may ignore them.”

TR: Current TPMS regulations state that if an aftermarket tire and/or wheel is installed before the vehicle is titled and the air pressure needed to maintain load capacity is different from the original tire, a new label must be placed over the original door placard indicating the new air pressure needed. Is this effective now or after a certain date? Who is responsible for enforcing the law and how will they communicate the requirements to all of the tire, wheel and new vehicle dealers in the country? What are the penalties, if any, to not have a revised label placed on the vehicle?

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NHTSA: “This rule has been in force since September 2005. It applies to new motor vehicles (up to first retail sale) except motorcycles and low speed vehicles with a gross vehicle weight of 10,000 pounds or less. Non-compliance could result in a safety recall by the responsible party that must be conducted without cost to owners. In addition, civil penalties could be assessed, up to $6,000 per violation and $16,375,000 for a related series of violations.”

(NHTSA communicates proposals and rulings through broadcast media and the Federal Register, among others. The Web site for the Federal Register is www.archives.gov/federal-register/index.html.)

TR: We understand that the current mandate for FMVSS 110 (selection standards for passenger vehicle tires and wheels) indicates that if components adding up to more than 0.5% of the total GVWR are added to the vehicle before it is titled, the total weight capacity of the vehicle must be reduced by this amount and indicated on a new label. Is this statement still correct or is there a revision on this?

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NHTSA: “FMVSS 110 requires that the combined weight of occupants (at 150 pounds each) plus cargo that is listed on the tire placard be accurate. Depending on the combined weight of dealer-added components, a vehicle could be overloaded when it is loaded to this weight. However, as your question illustrates, in a letter addressed to the National Truck Equipment Association, NHTSA is currently allowing dealers to add components to a vehicle without re-labeling as long as the combined weight of the components does not exceed 0.5% of the vehicle’s gross vehicle weight rating (GVWR).

“If the added components exceed that value, the dealer has two options: 1) correct the occupant and cargo weight by subtracting the weight of added components from that value and correct the placard, or 2) weigh the completed vehicle (with full fluids necessary for operation), subtract the vehicle’s weight from its GVWR, and, if necessary, correct the occupant and cargo weight. Until NHTSA issues a final rule, this is the requirement.

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“Regarding conformance with the requirement, NHTSA’s statute states that a vehicle dealer may not sell a new motor vehicle unless it conforms to all applicable safety standards. To affirm this, NHTSA’s enforcement office routinely inspects vehicles, sometimes at dealerships, and also tests them according to the FMVSS requirements.”

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