Pre-purchase GVWR and Pay Load Questions

[Hickory1199]

Everyone,

Trying to do as much research as is reasonably possible before making a purchase decision, and have come up against a question relating to trailer GVWR, axle capacity, and estimated payload.

As an aside, using the KYD spreadsheet it seems reasonable that a properly equipped 1-ton with DRW is enough truck to pull any fifth-wheel Grand Design builds. The hitch capacity is the limiting factor for gross trailer weight (actual, not rating). With the hitch as the limiting factor – and a little common sense applied – there’s simply no way a 1-ton with DRW GCWR should ever be exceeded. Please feel free to correct what may be an inaccurate conclusion here...

But back to the question of axle rating and trailers, I’m looking at three different models: the 374TH, 375RES, and 380FL. The 375RES and 380FL both have two 7,000 pound axles with GVWRs of 16,800 pounds.

First Question: How can two 7,000 pound axles support a GVWR of 16,800 pounds? Logic tells me that 2 * 7,000 = 14,000. Even if you subtract the estimated hitch weight of 2,900 pounds (leaving you with 13,900 pounds) there’s hardly any wiggle room for manufacturing variances in the axles.

Which brings me to the second question: How much pay load do most full-timers carry in their trailer? Being able to estimate the pay load should be a significant factor in the purchase decision, that is, “can the trailer I’m purchasing handle the weight that will likely be inside?”

While there are a lot of different floor plans to match a lot of different life styles, it looks like it would be very easy to exceed trailer GVWR. Am I way out in left field??

Thanks,
Frank

[bertschb]

Question #1 - You are correct. Two 7,000lb axles will barely meet the weight rating. Most RV manufacturers do this. Grand Design also used tires for several years that were right at the limit.

Question #2 - The weight people carry varies widely from person to person. I feel we pack light - very light compared to most people we see. We added about 1,200lbs of junk to our 5th wheel which included a washer and dryer.

[howson]

Everyone,

Trying to do as much research as is reasonably possible before making a purchase decision, and have come up against a question relating to trailer GVWR, axle capacity, and estimated payload.

As an aside, using the KYD spreadsheet it seems reasonable that a properly equipped 1-ton with DRW is enough truck to pull any fifth-wheel Grand Design builds. The hitch capacity is the limiting factor for gross trailer weight (actual, not rating). With the hitch as the limiting factor – and a little common sense applied – there’s simply no way a 1-ton with DRW GCWR should ever be exceeded. Please feel free to correct what may be an inaccurate conclusion here...

But back to the question of axle rating and trailers, I’m looking at three different models: the 374TH, 375RES, and 380FL. The 375RES and 380FL both have two 7,000 pound axles with GVWRs of 16,800 pounds.

First Question: How can two 7,000 pound axles support a GVWR of 16,800 pounds? Logic tells me that 2 * 7,000 = 14,000. Even if you subtract the estimated hitch weight of 2,900 pounds (leaving you with 13,900 pounds) there’s hardly any wiggle room for manufacturing variances in the axles.

Which brings me to the second question: How much pay load do most full-timers carry in their trailer? Being able to estimate the pay load should be a significant factor in the purchase decision, that is, “can the trailer I’m purchasing handle the weight that will likely be inside?”

While there are a lot of different floor plans to match a lot of different life styles, it looks like it would be very easy to exceed trailer GVWR. Am I way out in left field??

Thanks,
Frank

The basis of your calculations seems to be an assumption that the trailer is packed to the GVWR. If that's so, the 2,900lbs hitch weight is too light. If you're loaded to GVWR (16,800lbs) your tongue weight should be between 20-25%, or 3,360 to 4,200lbs. (At least according to the website towingplanner.com)

Taking the minimum (3360) that leaves 13440 on your axles. At the maximum tongue weight (4200) you have 12600 on the axles.

To your second question, Fran and I packed our 315RLTS over the GVWR very quickly. I have to move tools and other heavy items to my truck prior to towing. The relatively small difference between the empty weight and GVWR is often a complaint about our trailers.

My trailer came from factory weighing 9516lbs with a hitch weight of 1114. That's before the dealer-added battery and propane. The 315's GVWR is 10,995. GD's website says the trailer is 8994 unloaded with a hitch weight of 1065. Instead of the almost 2K of payload expected (10995-8994) I actually have <1400. To be fair, GD's website numbers do not account for the second air conditioner in the bedroom which is an option. FYI, the axles are rated at 5,200 each and my tongue weight is 1,300. (Remember, I have a bumper pull.)

Probably too much info, but I hope this helps.

[kevinpo]

there’s simply no way a 1-ton with DRW GCWR should ever be exceeded. Please feel free to correct what may be an inaccurate conclusion here...

You will need to check the truck including options carefully as it can be rather easy to exceed a truck's towing and weight capacities. With high prices of these type rigs you certainly don't want to buy one twice!

Regards,
Kevin

[bertschb]

... it seems reasonable that a properly equipped 1-ton with DRW is enough truck to pull any fifth-wheel Grand Design builds.

I would agree with this. We recently replaced our 3500 SRW with an F-350 DRW for this reason. If we ever decide to replace our (yet to be delivered) Solitude with something even heavier, I won't need to crunch any numbers with regards to towing capacity.

[TENN22]

Everyone,

Trying to do as much research as is reasonably possible before making a purchase decision, and have come up against a question relating to trailer GVWR, axle capacity, and estimated payload.

As an aside, using the KYD spreadsheet it seems reasonable that a properly equipped 1-ton with DRW is enough truck to pull any fifth-wheel Grand Design builds. The hitch capacity is the limiting factor for gross trailer weight (actual, not rating). With the hitch as the limiting factor – and a little common sense applied – there’s simply no way a 1-ton with DRW GCWR should ever be exceeded. Please feel free to correct what may be an inaccurate conclusion here...

But back to the question of axle rating and trailers, I’m looking at three different models: the 374TH, 375RES, and 380FL. The 375RES and 380FL both have two 7,000 pound axles with GVWRs of 16,800 pounds.

First Question: How can two 7,000 pound axles support a GVWR of 16,800 pounds? Logic tells me that 2 * 7,000 = 14,000. Even if you subtract the estimated hitch weight of 2,900 pounds (leaving you with 13,900 pounds) there’s hardly any wiggle room for manufacturing variances in the axles.

Which brings me to the second question: How much pay load do most full-timers carry in their trailer? Being able to estimate the pay load should be a significant factor in the purchase decision, that is, “can the trailer I’m purchasing handle the weight that will likely be inside?”

While there are a lot of different floor plans to match a lot of different life styles, it looks like it would be very easy to exceed trailer GVWR. Am I way out in left field??

Thanks,
Frank

At the last Grand Design Rally I attended (Deer Run in Crossville), there was a talk given by an industry expert on the loading of the trailers and the numbers he provided were not surprising, he stated (IIRC) something like 80% of all rigs going down the road are over the GVWR, and that most full timers average around 2,000 lbs of "stuff".

[Txfivver]

Hickory maybe I can give you more real world numbers as well. My new 2019 375RES with all bedding, kitchenware, 1/3 tank water, Onan generator, Splendide stackable washer/dryer, and optional outside kitchen scaled at 12700 on the axles and 3860 on the pin. I plan on full timing in this rig in a few years so will probably upgrade to 8K axles and disc brakes at some point. My dually's rear axle weight when hooked up was 7800 against a max of 9900 lbs and 4940 front axle weight against a max of 5900. As you can see it is pretty hard to overload a new dually but pretty easy to overload these big trailers. IMHO the bigger Solitudes you listed really need triple axles to really put them to their intended use.
Forgot to mention that Grand Design's website says my pin weight is 2900, and the empty weight was 14100, yeah right lol. The weight sheet that came with it said pin weight 3150 and empty weight was 14600, that's all without the propane tanks full or the second battery added. Big heavy son of a guns!

[Country Campers]

Frank
This axel question has consumed me for a few years, a fellow camper bought a new Jayco gvw was 10000# it had 2-4400# axels. I questioned him and he was told the same thing about pin weight.
Manufactures do this to cut costs and build something on the border line. I know people tow these types of units everyday but I would think the first thing I would do is upgrade the axels just to satisfy my own pet peeves.
The funny thing is the difference in cost from 1 size axel to the next is only a few dollars (maybe 50 or so) at the time of them building the RV. But after if we want to upgrade then it may cost 1000$ or more per axel.
Strange but it all about the penny saved is earned philosophy.
Brian

[Hickory1199]

@Txfivver,

Thanks - real world numbers mean a lot!! Great help, and you said exactly what was on my mind: GD needs to put triple axles under those bigger rigs.

[Txfivver]

@Txfivver,

Thanks - real world numbers mean a lot!! Great help, and you said exactly what was on my mind: GD needs to put triple axles under those bigger rigs.

You're very welcome and good luck in your search for a rig, you will NOT be disappointed with a Solitude I'm pretty sure. Just learn from everyone's experience on here, don't even consider pulling one of those big 3 without a dually, just not worth the worry.