Vehicle certification companies are familiar with the Gross Vehicle Weight Rating (GVWR) and Gross Axle Weight Rating (GAWR) and their importance to the labeling portion of the certification process.
Dealers and end-users are often accustomed to these ratings from an enforcement perspective (for driver qualifications, bridge weight limits, and state registration/title requirements) and may require mid-, final-, and modified-phase new vehicle manufacturers to change the original ratings to lower or higher Values to minimize driver requirements or maximize cargo capacity.
These ratings, awarded as part of the certification process, represent that the vehicle meets all applicable federal/Canadian regulations
Motor Vehicle Standards (F/CMVSS). Pre-first retail sale manufacturers — when a vehicle is licensed and titled by an owner in a particular state of the United States or sold and delivered to a first-level retail buyer in a Canadian province or territory — have the authority to make final ratings for a new motor vehicle. However, it is important to understand how ratings are set by the original equipment manufacturer (OEM) and the implications of changing those ratings before considering such customer requests.
From Title 49, Part 571.3 of the Federal Regulations, GVWR and GAWR are defined as follows:
- Gross Vehicle Weight Rating (GVWR) is the manufacturer's declared value for the laden weight of a single vehicle.
- Gross Axle Weight (GAWR) is the vehicle manufacturer's declared value for the load capacity of a single axle system, measured at the tire-to-ground interfaces.
Ratings are limits
GVWR and GAWR are maximum weights that the finished vehicle or individual axles can support and meet to meet regulatory requirements, durability, and OEM warranty goals. Since numerous variables can determine the GVWR and GAWR set by the OEM, ratings should be viewed as the weakest link in the chain. Therefore, only the OEM knows what components or limiting factors determine these ratings, so consultation with the chassis manufacturer is the only way to determine if and to what extent rating changes are possible.
For example, for braking systems, the F/CMVSS requires several tests to be performed at GVWR and GAWR, including for parking braking system and stopping distance. Assuming they are successful, the weight specifications for these tests become factors used in the chassis configuration and specifications assigned by the OEM.
However, the OEM may equip the chassis with suspension, wheels, axles or tires that have an overall GAWR greater than the GVWR. This is common for chassis up to the permissible total weight of classes 5 and 6, but does not automatically mean that a higher permissible total weight is possible.
More robust axle capacities allow weight to be distributed in one area to accommodate a greater variety of build configurations and applications for the same chassis when loaded to its gross vehicle weight rating without exceeding axle capacities. For heavier applications, where chassis are specified with a GVWR equal to the sum of the axle capacities, this specification standard restricts how the vehicle must be configured and loaded onto its GVWR. Otherwise, GAWRs can be exceeded when shifting weight forward or backward where the overall weight must be centered to meet axle limits.
Can you add axles to increase the GVW?
This leads to a common misconception that the GVWR can or must always be the sum of the GAWR values. However, this is not the case. Even if the chassis may have had more axles than originally, this does not mean that it is otherwise able to meet all the braking system performance requirements at a higher gross vehicle weight rating. Since other factors (e.g. durability) can also limit the GVWR, this weakest link value could be determined by another factor unrelated to the brakes. Additionally, incomplete vehicle documentation (IVDs) from OEMs often contain prohibitions on changing the GVWR, preventing the power stage manufacturer from using the OEM IVD guidelines as a basis for certifying the vehicle.
Warranty coverage may also be affected by these changes. Therefore, the only way forward would be if the OEM can provide a technical review or other supporting information to the contrary for a specific chassis.
What about the reduction in gross vehicle weight?
Another misconception is that lowering the GVWR is an easy process since the chassis can already handle more weight, so this is a better scoring scenario. While this may seem correct from a chassis capability perspective, such changes require OEM advice. A reduction in GVW could bring the vehicle into an area where more regulatory requirements apply (for which the manufacturer of the intermediate, final or modified stage would be entirely responsible).
For example, end users and dealers may require that a commercial chassis with a gross vehicle weight rating in excess of 10,000 pounds be modified to a value of 10,000 pounds or less to prevent the car carrier operating requirements from otherwise applying to the vehicle. This may invalidate IVD guidance and pass-through certification, as many F/CMVSS and other regulations apply to vehicles with a gross vehicle weight of 10,000 pounds or less, but not for vehicles with a gross vehicle weight of 10,001 pounds or apply anymore.
This includes dynamic crash testing and the base vehicle in a reduced GVWR scenario may not be able to meet additional requirements of the lower GVWR. In addition, a lower GVW could put the truck in a new emission class that the base vehicle is not equipped or able to achieve.
Approaching GVWR/GAWR changes
Because these ratings are not just arbitrary values on a label as it might seem, changing them for end-user applications is not as easy as putting a different number on a sticker. And there is no guarantee that a given chassis can have different ratings or accommodate the requested ratings. GVWR and GAWR changes must be evaluated on a case-by-case basis to first determine if this is possible for the specific chassis. If so, you must then identify component and/or programming changes required to make the chassis match the same model if it had been ordered from the factory with identical ratings.
For an indication of what is possible, review an OEM's product offerings to determine if a specific new chassis being considered for rating(s) changes is released by the OEM in the requested new rating configuration will. The data compared should include model, model year, powertrain, wheelbase, etc. where possible as these may all be factors in the established ratings.
If not, this indicates that even the chassis OEM is not producing any model variation in these reviews. Creating unique ratings that are not assigned by the chassis OEM would likely place the multi-tier manufacturer more (rather than less) responsible for the consequences and is not advisable. While dealers or customers may not share manufacturer compliance burdens, the impact of the OEM warranty can help put the prospect of GVWR and GAWR changes in a more understandable context.
Get an OEM Chassis Engineering Review
Again, these considerations lead back to the first step in the process of consulting with the chassis OEM to determine opportunities to change the ratings of a particular new chassis that has already been manufactured. To aid in this process, truck dealers can initiate OEM engineering reviews using the Vehicle Identification Number (VIN) to determine if a new chassis may have different ratings and what changes (if any) are required to effectively rebuild the chassis to do so that it corresponds to the factory configuration, it was originally ordered with the desired ratings.
The result of the technical review by the OEM – which usually consists of a short report letter identifying the chassis by chassis number – determines whether new ratings (up or down) are possible, as well as any necessary chassis modifications and additional guidance to overcome prohibition statements in the IVD .
The OEM report, if sufficient for the multi-tier manufacturer, can help provide the basis for creating assessments for the new vehicle to be certified. The dealer will likely need to make any component and/or programming changes required for the new chassis ratings in order to maintain the OEM chassis warranty for the customer.
Another important step is to conduct a thorough weight analysis to ensure no new ratings are exceeded. End and modified stage manufacturers can help customers by ensuring that newly contemplated ratings are still appropriate for their application, even if the OEM provides information to authorize the modification of the original GVWR and/or GAWRs support.
What about the revaluation of used vehicles?
Note that certifications and ratings only apply to new motor vehicles. Once a vehicle has been finalized and licensed and registered by an owner in a particular U.S. state or sold and delivered to a first level retail buyer in a Canadian province or territory, the obligation to certify, along with the transfer of reviews, ceases .
In a 2002 interpretation, the National Highway Traffic Safety Administration (NHTSA) gave the following response to the concept of used vehicle revaluation.
“NHTSA has long held the position that the only parties who can assign or change a vehicle's gross vehicle weight rating are the original equipment manufacturer, an amplifier manufacturer, or an convertor. The term "amplifier manufacturer" is defined in agency regulations at 49 CFR 568.3 as "a person who performs such manufacturing operations on an incomplete vehicle that it becomes a complete vehicle." Even if the refrigerated body is attached to the cab and chassis of your delivery van, Uhl Truck Sales cannot be regarded as the manufacturer of the vehicle's final stage. This is because the cab and chassis were in use at the time of these manufacturing operations
were performed."
If the used car gets a new body, does it have to be recertified?
In the same interpretation, the NHTSA defines entities that make modifications to used vehicles as modifiers and states the following in relation to their attempts to change ratings.
"Consistent with this description, a person making modifications to a used vehicle (i.e. a vehicle that has already been purchased for purposes other than resale) is not considered a 'modifier' as that term is used in the NHTSA regulations. NHTSA has stated in previous clearance letters that if a used vehicle is modified so that the originally assigned GVWR is unsuitable for the modified vehicle, the modifier may place an information tag on the vehicle stating its appropriate payload. See e.g. B. Letter to James Barber dated 2 April 1997. However, the Authority has noted that they would not accept the load weight stated by the modifier as the gross vehicle weight rating. This is because the modifier would not be able to assign a new GVWR to the vehicle as it would not qualify as an original or power amp manufacturer or as a vehicle convertor. In accordance with these interpretations, the NHTSA would not consider the value stated by Uhl Truck Sales on the sticker affixed to your vehicle as the vehicle's gross vehicle weight rating. The agency would instead recognize the vehicle's original manufacturer's assigned GVW of 29,000 pounds. Since the originally assigned GVW remains for the lifetime of the vehicle, there is no way to "re-certify" the vehicle with a lower GVW.
Can end users put their own certification labels on used vehicles?
No - Certification labels are the only legally recognized vehicle labels that contain GVWR and GAWR. These labels, along with the ratings, can only be assigned by the manufacturer of the power amp or modified amp. As previously mentioned, the certification process ultimately represents that a new vehicle meets all applicable motor vehicle safety standards. It is not advisable for anyone, especially end users, to claim that a used vehicle is capable of meeting newer standards that may have changed or been in force since it was certified. Therefore, no procedure has been established to re-certify a used vehicle and assign different ratings. Therefore, enforcement by transit companies can refute labels affixed to used vehicles to circumvent driver or other operational requirements based on these ratings.
The final result
Chassis OEMs are the only ones who know what limits their original ratings. Able to assist multi-tier new vehicle manufacturers in verifying that one of their products can meet all applicable regulatory requirements for different ratings than originally assigned during chassis manufacture and impact on chassis warranty.
Thorough weight analysis is required for all applications to ensure that ratings for a customer's application are not exceeded, regardless of whether new ratings are considered. There is no mechanism to change ratings for used vehicles that are no longer in the certification process where ratings are given - hence these final ratings are effectively given for the life of the vehicle, and road operator enforcement can ignore ratings on labels attached to used vehicles are attached.