Are They Meaningless? Tow Limits, Payload and Axle Load

[DewTheDew]

Originally Posted by jcl

Sure, but it will take quite a few paragraphs.

TL/DR version - they did have to make changes. The Euro hitch wasn't legal here. They had to spec a new one from an outside fabricator. They chose a rating for that new design. It wasn't the same as the vehicle rating.

Occam's razor says the simplest solution is the most likely. IMO, they weren't malicious. They weren't trying to downplay the towing capability. They just didn't know. There is abundant evidence to support that premise, some of it recounted above. It was a whole new market. Seen through the lens of North American pickup manufacturers, who these days compete to outdo each other on tow ratings, it seems silly. But it was different back then.

So I knew much of that, having owned an X5 myself. But the short version is that you do not know so you are guessing. And again, I don't care much about 2004 or whatever; this is 2020. Are you saying that BMW is still downgrading their X5 ratings because they still don't know? Thank you.

[BayouBiker]

I agree it is not Arbitrary, a handful of exceptions notwithstanding, for the vast majority of vehicles, the purposes are real and have a rationale. Though they generally apply to the rationale better when not towing for recreational purposes.

Seems like we have beaten payload to death but does anybody see payload differently than the apparent consensus? Seems like there is no disagreement on axle and tire limits either.

If not perhaps it is time to talk about towing limits.

[jcl]

Originally Posted by dznf0g

Jeff, I still say I never saw nor heard of any LD vehicle at gm with any lowering of gvwr.
Think about it, there are no LDs with a solo gvwr near 16k. If you are running a commercial combination you couldn't haul much below 16k....heck, my 1500 Silverado plus my AS is 17,400 gvwr.
There are options for lower gvwr 4500 series to keep them below 16k. But it is a lighter rear suspension. Again, think about it. If a commercial interstate light bulb manufacturer wants to stay below 16k, but need space, they need a big box truck...but they can't stand a harsh stiff ride. Thus less spring in back. It's NOT a label only option to skirt the law. If they want to haul twice as many light bulbs, they choose the hassles of cdl and there are many graduations up the gvwr scale, with hardware differences in all.

I know the Ford numbers far better than the GM ones. Had to look it up.

For the GM 2500, code C7A is reportedly the option to reduce GVWR to 10,000 lbs. In Canada it results in 9900 lbs. I had used HD to refer to trucks above 1500, just like Ford uses Superduty to trucks in that category. We are discussing 3/4 and 1 ton trucks.

[Bruce B]

Again, as a layman, the worst feeling towing experience for me was an overloaded, by factory assigned payload number, truck. The best towing experience was with a longer, under loaded by the same definition, truck. Of course I measured weights at the Cat scales...
I think most people understand this...

[jcl]

Originally Posted by DewTheDew

So despite Andy calling the GVWR arbitrary in a 1/2 ton pick up, and jcl digressing about heavy duty GVWR, I still say it is not arbitrary. They did not pull the number out of thin air.

My reference to HD was to HD pickups, including 2500 series. Class 2B and 3 (which can be termed medium duty), not class 7 or 8 HD.

[jcl]

Originally Posted by DewTheDew

So I knew much of that, having owned an X5 myself. But the short version is that you do not know so you are guessing. And again, I don't care much about 2004 or whatever; this is 2020. Are you saying that BMW is still downgrading their X5 ratings because they still don't know? Thank you.

It is an informed guess.

The X5 is still down rated for towing in the US market.

The X3 isn’t.

BMW sedans are also derated. My last BMW sedan was a 535. It would have done well towing. Peak torque at 1300 rpm. In North America the current 5 series is not rated to tow anything. But it is elsewhere. Suggests to me that tow ratings just aren’t important to BMW NA. Probably not part of their image. I don’t believe that it is because of the capability of North America’s drivers, but I suppose it could be. Maybe a litigious society. What is your guess? If we want to test the hypothesis that the manufacturer’s tow rating represents the maximum vehicle capability, and the manufacturer knows best, then we need to come up with something.

[dznf0g]

Originally Posted by jcl

I know the Ford numbers far better than the GM ones. Had to look it up.

For the GM 2500, code C7A is reportedly the option to reduce GVWR to 10,000 lbs. In Canada it results in 9900 lbs. I had used HD to refer to trucks above 1500, just like Ford uses Superduty to trucks in that category. We are discussing 3/4 and 1 ton trucks.

C7A is not simply a label change. It requires 6.6 duramax and crew cab. I gotta scratch my head for awhile as to why that reduces gvwr. It could be something as obscure as tire or wheel availability. Not sure I'll ever know, now being out of the loop and retired. But I guarantee you it is a hardware requirement.

[jcl]

Originally Posted by dznf0g

C7A is not simply a label change. It requires 6.6 duramax and crew cab. I gotta scratch my head for awhile as to why that reduces gvwr. It could be something as obscure as tire or wheel availability. Not sure I'll ever know, now being out of the loop and retired. But I guarantee you it is a hardware requirement.

I don’t have the full order guide but perhaps you can get it.

I built a Sierra 2500 online in both gas and diesel. The GVWRs were over 10,000. With both builds I had the option to select a 9900 GVWR at no charge. That is 4500 kg, our Canadian regulation limit for higher vehicle licensing fees, etc. The web site didn’t give me the order code. Extracts of the order guide online suggest that there are no consist changes, according to people who say they work for GM. Not sure about that.

I could do the same on the Ford site. I don’t now about RAM.

Note that this isn’t a result of other consist changes. It is termed reduced GVWR. It apparently has some complications in the US as it can result in some emissions changes, which kick in at the reduced GVWR.

[Collyn]

Originally Posted by tjdonahoe

How many of them engineers ever towed anything. ?

Me

A clapped out Forward Control Jeep.

How far?

Over 2000 miles from Kano in Nigeria across the Sahara to Algiers - by my 1940 QLR Bedford.

Will that do?

(Re who finally determines engineering design? In my era it was the accountants).

Collyn

[BayouBiker]

So although Payload and GVWR is not set arbitrarily, they are often set for licensing and considerations other than technical limits. We know this practice occurs for towing limits also, particularly in Europe, but also in the case of vehicles not marketed for towing. For these situations, we lack accurate guidance on safe technical limits. What is the most sensible approach for these situations?

[ROBERT CROSS]

^
Common sense, logical evaluation, butt sensitivity...in that order?🤓

Bob
🇺🇸

[dznf0g]

Originally Posted by jcl

I don’t have the full order guide but perhaps you can get it.

I built a Sierra 2500 online in both gas and diesel. The GVWRs were over 10,000. With both builds I had the option to select a 9900 GVWR at no charge. That is 4500 kg, our Canadian regulation limit for higher vehicle licensing fees, etc. The web site didn’t give me the order code. Extracts of the order guide online suggest that there are no consist changes, according to people who say they work for GM. Not sure about that.

I could do the same on the Ford site. I don’t now about RAM.

Note that this isn’t a result of other consist changes. It is termed reduced GVWR. It apparently has some complications in the US as it can result in some emissions changes, which kick in at the reduced GVWR.

I dont have access to internal documents since I retired. For some reason I cant copy the link, but I searched "silverado option code c7a". One result is from "GM authority". There is an order guide for 2019. Page 41 for c7a.

[dznf0g]

Originally Posted by BayouBiker

So although Payload and GVWR is not set arbitrarily, they are often set for licensing and considerations other than technical limits. We know this practice occurs for towing limits also, particularly in Europe, but also in the case of vehicles not marketed for towing. For these situations, we lack accurate guidance on safe technical limits. What is the most sensible approach for these situations?

Well, unless I had it from the horse's mouth that there are no hardware changes (which I maintain there are) you gotta go by the door jamb sticker.

[BayouBiker]

Originally Posted by ROBERT CROSS

^
Common sense, logical evaluation, butt sensitivity...in that order?🤓

Bob
🇺🇸

I suppose then when someone comes along and asks if a vehicle with no clear technical towing guidance can (presumably safely and comfortly) tow significantly over the OEM's non-technical towing limit the better response is nobody knows for sure but consider these issues....

The same thing would apply for nearly all payload questions.

Does anyone have an issue with this approach? It certainly seems more reasonable than taking a rigid approach with no sound basis to remain rigid to a particular viewpoint.

[dznf0g]

Originally Posted by BayouBiker

I suppose then when someone comes along and asks if a vehicle with no clear technical towing guidance can (presumably safely and comfortly) tow significantly over the OEM's non-technical towing limit the better response is nobody knows for sure but consider these issues....

The same thing would apply for nearly all payload questions.

Does anyone have an issue with this approach? It certainly seems more reasonable than taking a rigid approach with no sound basis to remain rigid to a particular viewpoint.

I dont think I am quite as liberal as your statements relative to the flexibility of the label numbers.

[jaybauman]

Originally Posted by BayouBiker

I suppose then when someone comes along and asks if a vehicle with no clear technical towing guidance can (presumably safely and comfortly) tow significantly over the OEM's non-technical towing limit the better response is nobody knows for sure but consider these issues....

The same thing would apply for nearly all payload questions.

Does anyone have an issue with this approach? It certainly seems more reasonable than taking a rigid approach with no sound basis to remain rigid to a particular viewpoint.

Don't be getting all crazy on us now. Next thing you'll be telling us that you remove the tags from your mattresses too!

In all seriousness, you suggest a reasonable approach.

Before we decided on Airstream, we were looking at giant 5th wheel trailers. As a 2500HD Duramax was my daily driver, I figured I could tow any of those things with ease. A short bit of research showed that I really needed a 1-ton dually to safely tow "by the numbers", in regards to pin weight and trailer weight.

On every camping trip and nearly every commute on the local highways, I see many 3/4-ton trucks pulling these large 3-axle 5th wheels. I don't recall ever seeing one rolled over in the ditch and I've never seen truck axles and suspension pieces along the side of the road, so somehow they can get away with it--all the time.

Practical experience says you can go over the limits. While that's not for me personally, I see it every day.

[BayouBiker]

Originally Posted by dznf0g

Well, unless I had it from the horse's mouth that there are no hardware changes (which I maintain there are) you gotta go by the door jamb sticker.

So your suspicion is that when GVWR is set primarily as a marketing tool to offer customers some flexibility with respect to licensing, taxes, and commercial hauling regulations and requirements that the manufacturer also takes overt steps via hardware to technically match the vehicle to the GVWR? As a consequence the GVWR most often accurately reflects true capability with enough certainty that it should be treated as hard and fast? Or would it be better to admit we just don't know?

[BayouBiker]

Fifth wheel towing is a much more stable situation and they generally have so much space underneath, there is little or no cargo in the truck. Even with 20% tongue a 15,000 lb fifth wheel won't overload the rear axle of many/most 3/4 tons and the design is inherently stable comfortably over highway speeds. I suppose if you go with a diesel and honor the license based GVWR of 10,000 you are over the advertised payload. Move up to a dual axle and there is no reasonable chance of sway and oversteer. Overhang towing, unfortunately , not so much.

[dznf0g]

Originally Posted by BayouBiker

So your suspicion is that when GVWR is set primarily as a marketing tool to offer customers some flexibility with respect to licensing, taxes, and commercial hauling regulations and requirements that the manufacturer also takes overt steps via hardware to technically match the vehicle to the GVWR? As a consequence the GVWR most often accurately reflects true capability with enough certainty that it should be treated as hard and fast? Or would it be better to admit we just don't know?

1) I doubt you will find this issue of derating on many dealers lots for retail consumption. Typically this is a fleet used option where their needs don't require max GVWR and dozens or hundreds of trucks purchased represent a lot of money relative to any fees and regulations they want to reduce. Kind of wish we didn't muddy the waters with all that.

2) Yes, I do believe that there are hardware differences in the derated trucks. What all is involved with that, I don't know, but whenever there is a configuration restriction, you can bet some component is driving it.

3) Since this derating is the opposite of our true question, relative to GVWR and payload, it's really moot to our discussion, right? We discuss, "can you go over payload and/or gvwr, staying under axle limits....and is there margin on all the specs which we can encroach upon". Correct?

4) I am in the camp, based upon career long periodic discussions as well as observations of product durability performance over time and miles in fleet usage, that the numbers should be respected. I never throw out the safety card, as that subject is way too subjective. I believe the hard and fast number adherence falls in this order of importance:

a) axle load limits & GCWR (equal importance)
b) gvwr load limits & receiver load limits (equal importance)
c) payload limits

Now, that said, I am squeamish that many will take these statements too far. If I am over payload by 100# and at 90ish% of axle capacities, I don't worry. I am comfortable that there is plenty enough of margin to account for that. But 4 or 500#....not so much.

[jaybauman]

Originally Posted by BayouBiker

Fifth wheel towing is a much more stable situation and they generally have so much space underneath, there is little or no cargo in the truck. Even with 20% tongue a 15,000 lb fifth wheel won't overload the rear axle of many/most 3/4 tons and the design is inherently stable comfortably over highway speeds. I suppose if you go with a diesel and honor the license based GVWR of 10,000 you are over the advertised payload. Move up to a dual axle and there is no reasonable chance of sway and oversteer. Overhang towing, unfortunately , not so much.

When I was looking at 5th wheels, pin weights on each of the (larger) units we were considering would have put me over axle limits on my 2015 2500HD Duramax.

I'm not challenging your stability/towability argument, I'm challenging the axle limit statement. How many times do you see a 3/4-ton truck pulling a gigantic toy hauler? I see it frequently (this is Texas, after all) and it does not take a leap of faith to imagine that some of these guys are over axle limits. In my experience, the RV sales guy (replete with 10-gallon hat and 5-pound belt buckle) said to me: "I don't know what axle limits you're talking about. You have a HD DEE-zull; your truck will drag this baby anywhere you want at 75mph...." It would appear that ignorance causes a lot of RVers to intentionally and unknowingly running a lot of these overloaded towing experiments.

On the Duramax forums, there are lots of examples of towing over the limits. The only thing that ever seems to break is the Bosch fuel systems and the complicated emissions reduction systems, and suspension failures are due to incorrect lift kits and the like. The stock axles and suspension components seem to handle these overload conditions quite adeptly.

I might even argue that data suggest the prescribed axle capacities can be routinely exceeded without negative consequences. But this is only an academic exercise for me. As a scientist, I do enough experiments at work. My dear family and expensive rig are too valuable to prove a null hypothesis with.