US SAE-J2807: How GVWR and GCWR Are Determined

[Wiredawg]

Friends,

While I was posting Ram Towing Guide on another Forum/Thread, I discovered the US SAE-J2807 Compliant on every page, I thought I would check it out. SAE site is here:

https://www.sae.org/standards/content/j2807_201602/

Not much help there as you have to PAY to download the document.

So, I found Truck Trend Network had pretty good info about it. Don't know how many of y'all ever checked this out, but for my part, I thought a few guys with a case of beer got together and SCIENTIFICALLY devised the criteria. Here it is:

http://www.trucktrend.com/how-to/towing/1502-sae-j2807-tow-tests-the-standard

I know threads aren't easy when you have to go off and read, so thought I would post this, see how many folks ARE aware of this, and read it carefully myself, then share comments. GOOD, BAD, or INDIFFERENT, this is how max loads and towing are determined on EACH truck.

Anyhoo, Let the comments roll.

Cheers, Ron

 

[jhenderson]

Good find.

 

[GAmes]

This is something that I believe was covered in a TDR article several years ago. My thought is that the GCWR rating that the truck goes into the testing with is determined by lawyers and bean counters. Add to that the testing isn't a requirement makes it pretty much useless data if you are comparing say a Ram 1500 eco-diesel to a Cummins powered Nissan.

 

[TFucili]

Figures don't lie, but liars figure.

 

[Wiredawg]

This is something that I believe was covered in a TDR article several years ago. My thought is that the GCWR rating that the truck goes into the testing with is determined by lawyers and bean counters. Add to that the testing isn't a requirement makes it pretty much useless data if you are comparing say a Ram 1500 eco-diesel to a Cummins powered Nissan.

I AGREE with you 100 percent! I had a 2009 Ram 4500 that Ram and/or SAE determined topped GCWR at 26Klbs and it performed beautifully at 33K lbs. It's the fact more lawyers I suspect than bean counters that I opted to upgrade to my current 2017 Ram 5500 to be under ALL weight ratings. There were some comfort and convenience upgrades that made it more worthwhile, but it was the numbers that drove the decision for me.

All that being said, here's how the lawyers and bean counters make thier determination.

Cheers, Ron

 

[AH64ID]

I’ll throw another metric into it.

Marketing. Why else would a 2500 and 3500SRW have different GVWR’s? The both have axle ratings to go above their GVWR.

What’s the point in a 3500 SRW if it’s not more capable than a 2500??

Now Ram has gone 1 step further with suspension/trans differences but the axles/frame/brakes are the same. Any one of these SRW trucks is weight limited by the rear axle tires, nothing else.


J2807 addresses GCWR, not GVWR. AFIK there isn’t a standard on GVWR like there is for GCWR.

 

[Cummins12V98]

GVWR, It's all about licensing and insurance!

 

[Wiredawg]

GVWR, It's all about licensing and insurance!

Ron,
I completely understand your position. I'm living proof ONLY using tire and axle max loading limits for truck/trailer loading AND ignored the rest of the noise for 18 years, no problems. I drove using EGT and temp gauges more than speedometer. In fact, I likely exceeded your limits by driving 75MPH pulling 18KLb Travel Supreme 70 - 75 MPH with 3/4 ton 00 Ram 2500 4x4 QC LB 6spd 3.54s from '00 to '02.

Your right about Insurance. That IS a big part of why I changed my mind to follow ALL the SAE recommendations.

See, we can both be right, as each of us SEEs our own situation. I don't fault you for yours. it's just natural our positions will be mentioned in these threads. You should see some of my posts back then... you'd been proud of my DISCUSSIONS on the matter.

I still haven't had time to study the SAE criteria, so when I do, I'll see if I can summarize the info.

Look forward to meeting you sometime... don't know if you like beer, but I do.

Til then, see ya on the TDR.

Cheers, Ron

 

[Jim W]

Most of you may know this already but another reason for the SAE towing spec is to level the playing filed between the big three in pick-up trucks for towing &hauling requirements.

Now this might be heresy to some: But all SAE specs are compromises between the corporations that sponsor SAE such as GM, Ford, Chrysler or FAC now, Caterpillar, John Deer and others. The spec is written by a committee of engineers some from SAE and others from the effective corporations. The specs are the bare minimum that the corporations and their engineers think they can agree to meeting when testing their product. Also the corporation Lawyers review the spec to insure that said corporations could not be held accountable in there is an issue.

I know for a fact that the bottom feeders (lawyers) try to use the SAE specs when they sue a corporation in lawsuits. I have been in a few of them over my years when I worked and it is amazing how they can twist the meaning of the SAE specs to suit their needs. So, that is why the SAE requirements are a bare minimum for testing to protect the corporations against lawsuits.

 

[slowmover]

J2807 has holes in it so big we could drive three abreast thru it.

So far as it matters:

1). Axle rating
2). Wheel rating
3). Tire rating

Are “the limits”.

Get the CAT SCALE phone app. Set up an account. Use it.

1). TARE Weight. The day I buy a vehicle I transfer the few items permanently kept in my vehicles. I drive to the truck stop and top off the fuel. Hop on the scale.

1). That set of numbers represents the TARE. The adjusted (true) lightest weight of my vehicle.

2). The door sticker limits are next. The range between those (scaled low set just recorded & max limit from sticker) determines what I can load onto the vehicle IN TOTAL.

Patched tires prohibit
Broken spring prohibit
Lack of CDL is a limit
Etc.

Whatever the trailer and hitch type, an RV needs full fresh water & propane plus a good camping load. All passengers aboard.

Do these immediately one after another.

Three Pass Scale Method

1). Top off fuel. Hop on scale with hitch adjusted (tensioned).

2). Second Pass (not 5’ers). Relax hitch tension completely. Don’t remove.

3). Both types. Drop trailer. Return to scale solo vehicle only.

Get scale tickets. Keep as permanent record with TARE weight.

J2807 is worthless.

The above (Ron Gratz at RV.Net circa 2010) is gold. Most every towing problem starts a solution with questions derived from these scale values.

(Tire Pressure on truck is where most of you screw up. Too much. Dead-on or 5-psi over with LT LR-121. Adjusting higher is one bad mistake as you’re trying to adjust the handling. You make emergency recovery LESS LIKELY. Make improvements with larger FF/RR anti-roll bats and/or rear Panhard Rod. Better than entry level KONI, BILSTEIN or FOX shock absorbers).

— All trailers should be dead-level for travel (carpenters level across doorway. Inside bubble).

— Steer Axle Weight should be the same in 1 & 3 (close; except with heaviest. ASK).

— Combined Vehicle should stop as fast or faster than solo loaded vehicle. Test.

— Mirrors should have convergence 100’ past trailer (see state law). Eagle Vision strap-on with convex better than stock mirrors. (Amazon).

— Any trailer needs the Lippert (TUSON) trailer mount electronic anti-sway.

Same for the TUSON brake controller. Factory or Prodigy ain’t gettin’ it.

Now, you needn’t waste time with J2807. You want an education, find the original 1965 SAE paper (Bundorf, et al).

You’ll find the present paper (and hitch recommendations) are lies. Which you can test out for yourself.

You’re responsible.
Not Ram or SAE or the RVIA.

(Who was the guy here at TDR, ages ago, had as his tag line,
“I am my own warranty station”[?] )

.

 

[Wiredawg]

(Who was the guy here at TDR, ages ago, had as his tag line,
“I am my own warranty station”[?] )

Thanks for the post. Manufacturers post GVWR, GCWR, and GTW and J2807 is (I've read) how they do it. Again: "GOOD, BAD, OR INDIFFERNT." There are other elements that are considered by manufacturers: brakes, frames, springs....etc. Might be full of holes, but better than nothing. So, IYHO, why not use JUST tires and axles in the GCWR and GCWR? Wouldn't it be easier?

There are a few who have used YOU ARE YOUR OWN WARRANTY STATION, but RustyJC comes to mind the most. Others may chime in on this as well.

Cheers, Ron

 

[slowmover]

The total of limits is greater than so called ratings.

Ratings are arbitrary. MOST VEHICLES HAVE NO RATING AT ALL. Or some number they admit they never tested.

Pickups are a flawed design. Poor road vehicles alone, worse when towing.

A worthy comparison is with the Malibu or Charger or. Honda Odyseey or Nissan NV2500. Or whatever. Not available as no one would want a pickup. Family transportation with an upgrade for trailer towing. As in 1967.

But the profit is in pickups. Why the lies are inside J2807. In 1965, a better than today’s pickup tow vehicle was available. The family sedan.

The pinnacle of which today is the Mercedes’s design Charger/300.

The new guys with their twenty years RVng in a pickemup have no clue. Nor a desire to review 8th grade physics. Rocket science it ain’t.

So, no, J2807 isn’t useful. It’s more whitewash.

I think it was RustyJC. Thanks.

 

[Timd32]

Serious question on Axle/Tire ratings, are the ammount of and or type of brakes part of those ratings at all?

Are those figured in to the mix?

 

[Wiredawg]

Serious question on Axle/Tire ratings, are the ammount of and or type of brakes part of those ratings at all?

Are those figured in to the mix?

Short Answer: I would say yes, because on the vehicle door plate, it lists maximum weight for the axles, the tire size, tire rating, and air pressure for the weight numbers listed.

Long Answer: That's why before I purchased a truck that had the high enough trailer tow ratings (GCWR), I exceeded everything EXCEPT tires and axles. I ensured all my equipment was optimal, especially trailer brakes, didn't hurt I had a 2000 Travel Supreme with triple 6KlB axles. Every year, I jacked up the trailer, pulled each hub and repacked the bearings, and inspected/adjusted brakes.

AND: As many rednecks experience and folks who know manufacturing processes, there is anywhere between 5% and 25% headroom built into most components, it just understanding EXCEEDING them shortens their life, requires adjustments (drive slower and increase following distance), and increased maintenance intervals.

Cheers, Ron

 

[Cummins12V98]

My Dad many years ago had his 94 2wd and 34’ HitchHiker 5er in a early TDR mag saying

“I AM MY OWN WARRANTY STATION”

 

[Wiredawg]

My Dad many years ago had his 94 2wd and 34’ HitchHiker 5er in a early TDR mag saying

“I AM MY OWN WARRANTY STATION”

Ron,

What was your Dad's handle on here?

Cheers, Ron

 

[SnoKing]

(Who was the guy here at TDR, ages ago, had as his tag line,
“I am my own warranty station”[?] )

Thanks for the post. Manufacturers post GVWR, GCWR, and GTW and J2807 is (I've read) how they do it. Again: "GOOD, BAD, OR INDIFFERNT." There are other elements that are considered by manufacturers: brakes, frames, springs....etc. Might be full of holes, but better than nothing. So, IYHO, why not use JUST tires and axles in the GCWR and GCWR? Wouldn't it be easier?

There are a few who have used YOU ARE YOUR OWN WARRANTY STATION, but RustyJC comes to mind the most. Others may chime in on this as well.

Cheers, Ron

Speaking of warranty, the GVWR and GCWR are manufactures numbers related to warranty and truck classes(GM just blow a hole in truck classes with 2500 having more that 10K GVWR). At the weight stations across America it is the Federal Bridge Weight Laws that are enforced. No pickup is going to exceed them. So states like our home State of Washington license tonnage. In most cases their formula creates tonnage above the vehicles manufacturers GVWR. Both my 2001.5 8800 and 2015 11,700 where/are licensed to 12K. I could up either to 14K if I wanted for a little more in fees each year.

 

[Cummins12V98]

Ron,

What was your Dad's handle on here?

Cheers, Ron

I will have to ask him.