sh410 wrote:
From FE's post:
"GTW is what a trailer is supposed to weigh when delivered to the new owner. The CCC placard will list the maximum amount of cargo that can be added to the GTW. When added together those two cannot be more than the vehicle’s GVWR. At that point the only way to find the pin weight is to weigh it. Once the pin weight is deducted from the GTW the remainder - GAW - is what’s being carried by the axles. That weight cannot be more than the GAWR. OE tires must have a total load capacity equal to or greater than GAWR."
According to Dexter Axle:
"The maximum load carrying capacity is limited to the lowest load rating of any individual component selected. For instance, the load rating of a pair of wheels may be lower than the other axle components. If the is the case, the load rating of the total assembly must be reduced accordingly. As a specific example, if a pair of wheels are rated at 1500# each and are use with other components rated at 4000#, the maximum load capacity will be limited to 3000#. If two tires rated at 1400# each and are used on this assembly, then the maximum load carrying capacity is limited to 2800#"
Dexter applications manual
In example from placard you posted, according to Dexter the axles rating are derated to the total of load rating of the tires.In example from placard you posted, according to Dexter the axles rating are derated to the total of load rating of the tires.
Can you post a reference that OE tires must have a total load capacity equal to or greater than GAWR?
Thanks to Jminlin, I can:
From NHTSA Title 49: S4.2.2 Tire load limits for multipurpose passenger vehicles, trucks,
buses, and trailers.
NHTSA wrote:
S4.2.2.1 Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR
of the axle system as specified on the vehicle's certification label
required by 49 CFR part 567. If the certification label shows more than
one GAWR for the axle system, the sum shall be not less than the GAWR
corresponding to the size designation of the tires fitted to the axle.
Hi Folks,
Sorry just catching up to the party. I read there is talk about the tires, and the axle being what makes up the GAWR.
I am referring to above in the Blue I highlighted. The RV manufacture is the one who controls the GAWR of the trailer they are building.
And as Dexter points out the "weakest" member in the running gear becomes the limiting factor. In most cases the normal components that go into the GAWR declared are:
- The rating of the axle itself
- The rating of the springs, (leaf spring)
- The rating of the rims
- The rating of the tires
The weakest of these components will be the driver of the GAWR.
On a tandem axle setup, they can use, 5,200# axles, ST225/75R15 LRD tires and rims (2,540# each) and hook up a set of 5,000# rated leaf springs. This would create a GAWR of 10,000# There is more tire rating and more axle rating but in this case the springs limit the running gear.
What I listed above is from my TT. My TT builder took the conservative route. On purpose they rated the TT GVWR at 10,000# along with a 10,000# GAWR knowing the truck is holding the tongue.
I asked them about this and they stated they did it this way as a saftey factor. They create the GAWR rating so the running gear can hold the entire GVWR of the TT. The camper is not made exactly even left to right nor do people load the camper exactly even left to right. Since the truck is holding the tongue 10 to 15% is easily obtained as part of the tire loading saftey factor.
Realizing the excellent points discussed in this thread, what we as a camping forum can do, is to help educate our fellow camper friends to look for this when they buy a new camper. If the GAWR is less then the GVWR then the buyer must take even extra precautions to not overload the running gear.
It is clearly marked on the VIN plate but understanding what it means is often not known to the buyer. The new "light" or "ultra light" campers are more more prone to over loading if weights are not realized. Having a 30 or 32 foot camper and only a 1,200# CCC is not much for a camper that large. Some use new lighter components and some use semi lighter components and limit cargo capacity and drop the running gear size.
I myself after learning what I have will not buy a camper that does not have running gear that cannot hold the entire GVWR. Not every TT manufacture derates the running gear but many do. Why??? Possibly to save a few bucks making the TT. The cost at the OEM level is not much in relation to the MSRP of the TT. The world of pop ups is even worse then TT's for this rating issue. Found that out trying to help my son buy new tires for his.
John
