Axle ratings where is the weak link?

cooldavidt wrote:
I just went through this analysis.

The manufacturer puts a GVW on the door.

That's, by law, the max of the total vehicle weight with ALL the load init. No exceptions.

That is perfectly right, but understanding the words is hard.
"By the law" in this case mean registration.
You can have 30,000 lb axle, that would put vehicle in CDL requirements, so manufacturer downrate the axle to 10,000 lb and you pay lower fee as the result.
Meaning the axle rating on the truck is paper rating and have very loose connection with actual technical rating.
I did some commercial hauling in my life and have never been questioned about exceeding GVWR. I had 10,000lb + forklifts on my F450 several times just fine.
Than it seem to be "west coast" adventure where 350 Ram duallies are pulling car hauling trailers with 4 and even 5 vehicles on them.
They drive thru all the weight stations.

What about getting it stopped, what is the GVW for that truck and still meet some kind of stopping spec. Where do you find that info??
Maybe that has something to do with the low GVWR?

The OP question of why they did it is a good one, it only happens in these light trucks, on heavy trucks if you look at the GVWR it will match the GAWR of the front and rear axles.
eg, 12,000 pound front
40,000 on the 2 rears

The tag will then read 52,000 GVWR...

I will delete additional post that are Off Topic.

Wayne
Moderator

Each of us must perform due diligence to examine the data available from the manufacturer as regards payload capacities. In my case that meant digging through the Ford websites and tables to determine (for my specific model) the wheel rating, the axle rating, and the numbers for front, rear, GVW, and GCVW. Then go weigh the truck empty with a full tank sans tail gate at a certified scale. Don't trust the local dump, CAT scales are better.

Take all this information and compare it with the camper dry weight, then add what you expect to load into it and any ancillary loads (trailers, extra batteries, tanks, generators, etc.). You should be able to come to a judgement as to whether or not the rig is going to be at or under an acceptable weight for your purposes and locality.

All this discussion over legality is entertaining but does not actually give a person all the useful feedback that they need. In my job as a DOT worker on state roads and interstates I see many examples of overloaded rigs that have bad outcomes, but they tend to be smaller trucks attempting to tow large fifth wheels at high speeds. I have not come across any TC's that have wrecked due to overloading YET. Most RV's are hauled away in pieces, and yes, they do cause injuries and fatalities, HOWEVER most accidents are caused by excessive speed, weather, or inattentive driving. The most common accident on the interstates is driving off the road for no good reason!

Stopping distance and handling characteristics are critical factors in any camper decision for me. Suitability for my truck entailed far more than just weight, and center of gravity was perhaps just as important.

My gut reaction to the OP's question is one of incredulity: How can that DRW truck have the same GVW as my '06 SRW? I feel your pain! I guess the story is in the numbers. Someone on this forum has the links he needs to find all the OEM data. In my case the wheels were the weak link. With a dually I would think the wheels and tires would NOT be the achille's heel.

In any case, if the truck is licensed properly and is modified to carry the payload safely, I don't think that the Port of Entry guys or the State Police will be giving it a second look -- at least here in Idaho, where TC's are everywhere.

Run your numbers and if they are close, add some bags or Stableloads or whatever and see how it drives. Or walk away from it and try something else. In any case good luck with the outcome!

So I lied above. I have one full re tard example from back in hi school when I was a fleet mechanic for a landscape outfit.
Had a brand new D350 ram 4x4 dually. Boss insisted on putting a dump bed on it.
That truck get beat like a rented mule.....on a good day. On bad days it was limped back to the shop or busted in half on the side of the road. In 30kmi I replaced both rear axle shafts at least once, bent, bearings, brakes idk how many times, AND split the frame both sides over the rear axle.
5klbs was a daily occurrence, just bottoming out the springs hauling a load of wet beauty bark. But when the truck would show back up with a couple 36" root ball trees with full leaves AND the NH785 skid steer with a tree spade on the front, both IN the dump bed, and a 30' tag trailer loaded with trees behind it, was when I usually got overtime work fixing it!
Seeing what was loaded on that old school C channel frame on a daily basis tells me that there's pretty much not anything I could put in the back of a truck, including a 6klb camper, as long as the wheels and suspension were up to it, that would break it.

NOW to qualify about duty cycle and factor of safety....... Those ratings are meant to protect, IMO, someone who does not have the experience with or great understanding of the tool (truck) they are using, or those that prefer very conservative factors of safety.

Like everything in life, this too is a compromise.

AAA summary by state

Great info from AAA regarding weight laws.

Thank you cooldavidt.

Reddog1 wrote:

bighatnohorse wrote:
... Can you imagine what people would do with a printed axle rating higher than the rim/tire capacity?

Actually no need to imagine, many of our forum members do just that. If you look at the photos, most will be obvious.

Wayne

All day long and twice on Sunday!
Back on topic, OP, duty cycle figures in too. Is this occasional work for the truck or is the camper getting loaded on there and staying there?
Another unknow that we, unless design engineers can't possibly know. But what we do know is what we see every day, i.e. Heavily loaded _______brand trucks being run down the road with estimated ______lbs on the back. How many decent trucks of ______gvw you see or hear of sitting on the roadside with a bent frame or snapped off spring mounts? Aside from old rusted out beaters, that pic of the Ford dually on here with a big camper is the ONlY one I've seen in 20 + years and half the country of travels.
Why? Because unless you go full re tard, the truck will handle it.

donn0128 wrote:
Actually David your wrong unless by Vancouver your in Canada. BC is the only state/province that I have heard aboit that enforces mfg GVWR numbers. No body actually cares until you are envolved in an injury accident.

I work for a Canadian construction company (1000s of vehicles and trailers) as well as Canadian friends with trucks and trailers, and yes the canukians do enforce gvws more strictly than the US. That said David is mistaken about tires and wheels. Already has a dually so stock tire and wheel ratings are well within spec with let's say a 3ton payload.
Plus we know AAM rates that axle around 10klbs. Good there too. Springs can be upgraded easily.
That leaves frame and spring mounts as potential weak links.

If one wants to go "pseudo" by the numbers, since none of us can realistically calculate the actual design strength of frame and spring perches.
Lose the "gvw" and class load limit ratings and look at the vehicles.
Take the same design truck, likely newer model with same chassis (frame and hard parts), base model, gasser single cab etc. look at the payload (which is likely north of 6klb for a dually). Now compare the curb weights to a 4x4 high optioned crew cab diesel. Say you have 1000-1500lb different. Now look at how much of that extra weight is carried by the front axle. 4wd, about 75% is front axle, diesel, all front axle, extra cab, over 50% front axle.
What you'll find is that the rear axle is carrying a small percentage of the additional weight. Subtract that 500lbs or so from the Max payload of the stripper/gasser truck and that is reasonably what the rear frame etc is designed to carry.

op wrote:
I have read that this axle is rated higher than the GM rating of 8200 by the axle manufacturer, (current gvwr rating of 11400) so why did GM only rate the axle at 8200 lbs and where is the weak point after the aftermarket suspension upgrades ?
Thanks aging for the help , this is a learning process and the help is appreciated
Mike

I think it was in the '11 era GM finally uprated the same 11.5" AAM axle from 8200 up to 9375 rawr. Prior to '05-'07 era the DRW has a higher 8700 rawr. For some reason GM mis calculated the one ton DRW market and lowered the trucks rawr numbers. Sometime in that era GM made a press release to that affect.

Big up roar with some Commercial haulers websites as some owners and fleet mgrs stopped buying them.
Ford was at 9000 and Dodge at 9350 rawr numbers so GM users were at a big disadvantage on payloads.
AAM rates the axle in the 10.5 or 10.8 lb range I think so as was mentioned tires/wheels and rear spring pack will be the weak links.


Having pulled heavy GN trailers legally multi state with a dot number and owning several truck campers and pulled several personnel rv trailers Legal weight issues are always a hoot on a rv website with opinions all over the place.
OP if your concerned about vehicle weights then contact your state or provinces size and weight folks.

I really have a hard time with the sky is falling misinformation. Now we have posts that are saying your insurance does not cover you if you are at fault, this is one of the reasons we get insurance. I just shake my head, and wonder if they have any idea as to what they are insuring.

We are sliding Off Topic. The OP ask a question. "... so why did GM only rate the axle at 8200 lbs and where is the weak point after the aftermarket suspension upgrades ?". Lets get back to the question.

Wayne