Trailer discrepancy between axle ratings and GVWR.

[DMax82]

Hey all, I'm hoping for a little clarification on something. Next week at Ritchie Brothers in Nashville they are actioning off a large number of generator trailers. Looking at the data plates on a lot of them, I see that the axles are rated for 6000 pounds each (dual axle trailers), yet the trailer's GVWR is only 8850 pounds instead of the 12,000 pounds I was expecting. I feel like on most trailers I have seen the GVWR is at least equal to the sum of the axle ratings, if not higher. Any ideas as to what could be going on here? The frames look really stout.



 

[Ianab]

As it's a piece of machinery that's probably the actual weight of the rig. And that's what you would use to calculate your safe / legal towing and combined vehicle weight. The axles are rated a little higher than the minimum needed, which seems like a good thing.

Some jurisdictions also calculate road taxes based on weight, so you dont want to be rated any higher than necessary.

[rusticretreater]

https://www.constructionbusinessowner.com/equipment/understand-your-trailer-gvwr-gross-vehicle-weight-rating

A confusing article, but it contains the following quote which I believe is the answer to your question.  What this means is that the trailer weight(which sits on the suspension) is accounted for, so you should only carry what the GVWR amount is when you load the trailer.

In the first case, the capacity rating of that trailer is determined by subtracting the weight of the trailer from the GVWR of 12,000 pounds. If the trailer weighs 2,600 pounds, then the payload capacity of that model is 9,400 pounds.

The problem is that manufacturers are allowed to rate their trailers using different methods.  This seems pretty dangerous to me but that's what the article says.  I would say you need to find a definitive statement of payload capacity in the manual.

[SawyerTed]

The manufacturer intends the trailer to be dedicated to the generator.  They don’t want people to haul alot of other stuff in addition to the generator.  

[Walnut Beast]

They may be going by one axle and not two. For example on my Gooseneck the tag of  trailer weight is the basic trailer of the given length with no options. And on the axels for example I’ve got two 12k axles but it’s rated at 30k. They sell it as the 25,900 to keep it under the fet tax. They will rate them up to 30 k but you will have to pay the 12% tax. The 416 trailer that uses two 16k axels is rated for 40k.

[sprucebunny]

Looks like it has 15" D rated tires. The weight rating of the tires is 2150 times 4 = 8600.

Just a guess.

[charles mann]

Could the generator and wt. of trailer frame weigh 3150 lbs? That would account for the lower gvw, depending how the trailer is constructed and the amount xfrd to the truck. My gn has 2 10k axles but tlr gvw is 24,000 bc 20% of the load is xfrd to the tck, buy moving the axles further, compared to a tlr with the same axles being rated at 20k. 

[YellowHammer]

The manufacturer or even the current owner can derate the trailer to whatever they want.  I've done it myself, lower the official stickered GVWR of a higher rated trailer to what I wanted to get me under the CDL limit.  I've also got one boat trailer that's rated for the weight of the boat, even though the trailer axles and frame can carry another couple thousand lbs.    

So I guess it wouldn't be a surprise that a generator trailer is derated to carry the generator weight even though the axle ratings are much higher.  

 

[caveman]

The manufacturer or even the current owner can derate the trailer to whatever they want

Robert, thank you for sharing this.  John and I have been considering selling our tandem dually gooseneck trailer due to the enthusiasm of the Florida Highway Patrol commercial vehicle enforcement folks and their proclivity to write big tickets.  Neither of us have a CDL.  The trailer's current GVWR is around 25K.  

I really like the trailer and the way it pulls and carries the load but this December, it may be time to have it rated for less weight.  That may even save us a bit on the tag as well.  

The tires on the generator rig seem like a reasonable explanation to the weight rating on that trailer.  

[YellowHammer]

Here's what the steps are in Alabama, but I got the 2 step procedure from the trailer manufacturer, PJ trailers.  

First, I had to go to my local DMV where I get the tags, told the county clerk what I wanted to do and we picked the derate weight for the trailer that would get me to exactly 26,000 lbs based on the GVWR of my F250 truck.  We literally picked out the number from thin air, even discussed if we should set the weight to get to 25,999 lbs, or 26,000 lbs.  We decided on 26K and the DMV proceeded to issue me a new registration weight rating on my license plate form.  So now my trailer was registered in the state with the new rating.    

Then, I simply photographed the new license registration and sent it to PJ Trailer home office, (not the dealer), and they issued me a new manufacturer originated GVWR sticker.  The axle ratings didn't change, nothing changed except the overall GVWR was exactly what I wanted.  A few days later, my new sticker arrives in the mail, I pull off the original and this one goes on in it place.  Done, and that easy, all legal, no hassles, just a little time and coordination.  Easy.

 

[DMax82]

Thanks everybody for the thoughtful replies! My original thought was to use one as a base for a dump trailer, but upon inspecting them in person I saw that they only had about four feet between the wheel wells. I am still thinking to pick up some though, because I suspect they will go cheap, and I think I will find a lot of uses for them.

The funny thing is that some of the trailers have the axle ratings and GVWR match up. I hope to go inspect again this week, and I'll check on the tire ratings.



 

 


 



 

[rusticretreater]

So what I got from this is:

nobody really knows how much a trailer carries unless they know the rating system used by the manufacturer or it is explicitly stated in the documentation;

there is no consistent method of rating a trailer in the industry;

you can legally change the rating of a trailer based on preference;

it is next to impossible to explain this to a lawmaker, trooper or a judge;

the GVWR can change if you upgrade your tires.

And you thought buying and selling logs was dicey!

[Walnut Beast]

Upgrading your tires doesn’t change the GVWR if other components are not adequate. 

[YellowHammer]

Walnut is correct,
and to clarify, there is a reasonable system.

The axle ratings are the core of the trailer rating system, but no matter what, you can’t legally increase or decrease a formal stickered GVWR rating unless you get the trailer manufacturer approval.  The rating on the sticker is the rating to the judge or state trooper.  You can also increase any or all component physical ratings, but generally, the axles are the core component that stays the same.  Only the manufacturer can change a GVWR rating sticker.

As an example, if the axles are manufacturer rated (stamped on each axle) at 10,000 lbs each then that’s the max they can carry, regardless of tire rating.  So if a state trooper puts scales under the axles, each can’t have more than 10k.  Some manufacturers simply rate on axles ratings, and so the trailer would have a GVWR of 20K.  That’s normally how a bumper pull trailer is rated, for example one of mine has twin 7K axles, and the trailer is rated GVWR 14,000 lbs.

For gooseneck and fifth wheels, the manufacturer normally expects a load to the truck bed, and adds, but sometime not, the carrying capacity of the bed hitch.  Generally for a double 10,000 lb axles they will rate the trailer with 5K on the gooseneck, so the twin 10K axle trailer is GVWR stickered at 25K.  If a trooper weighs it, it still must not have more 10K per axle and no more than 5K on the gooseneck.  

If the trailer is derated like I did with the DMV and manufacturer, for example to 15K lbs (as an example) then the cargo can be shifted to any location as long as it and the trailer, when on scales, weighs less than 15K lbs total, there is no more than 10K on one axle and there is no more than 5K on the gooseneck hitch.  

Although you can increase the physical safety margin and carrying capacity of the trailer by upgrading tires or suspension, (I do it routinely, generally one increment), the formal (legal) GVWR can not be changed unless the manufacturer gets involved and sends a new sticker.  Simple as that.  The tires, or the suspension may carry more, and yes, the physical safety has been increased, but it won’t change the legal GVWR.

[Ianab]

The rating is also a "weakest link" thing.
 
Every part has to be at Least up to the rating. Frame, axles, tires, springs, tow hitch etc. Then there are the legal / tax issues, and what the tow rating of your vehicle is. 

Having tires or axles rated higher than technically needed is no problem, apart from some extra cost, but you increase your safety margins as well. 

On the voluntary down-rating thing. We can buy all sorts of light trucks second hand from Japan. But if your vehicle is over 3.5 tons, you need a truck licence to legally drive it, which is a pain if you just want to convert it into a small camper. So the importers often offer the option to register 4 or 5  ton GVM trucks as 3500 kg. (They might be 2,000 kg empty). Means it's legal to drive on a car licence, as long as you aren't "fully loaded".  The original Japanese plates might say 5,000kg  GVM, and the vehicle is physically built to carry that. But you can cruise around with a camper body on the back at ~3,000 kg, with a standard car licence and less road taxes. Same truck delivering 3 tons of gravel would need the 5 ton GVM rating, and a light truck licence. 

So yeah, there are legal / tax reasons to de-rate GVM, as well as the "weakest link" physical ratings.