Math Check - Tell Me Where I'm Wrong

[richiek]

Hello All:

I wanted to reach out to the community in an attempt to have a few more eyes check the numbers on a new truck/fifth wheel matchup. Details below:


Road Warrior 425 5’er
GVWR: 18k lbs
Dry Weight: approx. 15k lbs


2015 GMC 3500 HD Crew Cab DRW Duramax 6.6 4x4
Curb Wt: 6,892 lbs/7,646 lbs (used 8k just to be safe)
GVWR: 13,025 lb.
GCWR: 30,500 lbs


Running the numbers on rvtowcheck.com it appears that with a 25% pin wt the max fifth wheel weight comes in at 16.5k lbs. (20,625 lbs at 20% pin wt.) which is just about my units dry weight and won’t allow for many (if any) future dirt toys. What am I doing wrong with these calcs? Or will the GMC DRW just not cut it for my 5’er?Thanks in advance for any thoughts/advice.

Richie

 

[danemayer]

You've got 3 curb weight numbers: 6,892, 7,646, and 8,000. What do those numbers represent?

 

[cookie]

I'm not sure I understand your numbers.
If the GVWR of the RW is 18K and you have 25% pin weight it will put 4,500 lbs in your truck. 18K is the max weight of trailer and cargo.
Your GMC has a GVWR of 13,025 and using your guess of 8K for the curb weight, when hitched up your GVW will be 12,500 lbs.
Also the GCWR of your GMC is 30,500. So the curb weight of 8K plus the GCWR of 18K brings you to 26,500 lbs.
You will be fine with that truck.
Another thing worth noting is that your really need to get everything weighed. Not guess.
I hope this helped rather than add to the confusion.

Peace
Dave

 

[OEFVET]

Also when it comes to toy haulers your pin weight will actually be less by putting 1000lbs of
Toys in the rear. You should check your pin weight with some weight in the rear.

 

[Doublegranch]

Work your numbers using your "Payload" weight for your truck as well....I have a 2500 Ram diesel and was going to upgrade to a Sundance XLT, hitch wt 1660, My Ram will haul a combined wt of 20,000 lbs but the payload is only 1840 lbs...so with my 55 gal bed tank and the hitch wt I am overgross.....I am not sure how many are paying attention to the max payload their truck can handle.

So now I will stay with the North Trail TT until I buy a new 3500 Ram.

 

[MCTalley]

Typically, a well-loaded fifth wheel will have around 20% on the front pin. As you mentioned, going with the 20% figure on the website, you came up with a 20K trailer (well over your trailer's weight rating). As OEFVET mentioned, once you throw some toys in the garage, that figure will decrease into the teens. I think you are fine.

 

[scottyb]

I was running around 13,650 on my 2013 F350 DRW with a fully loaded (actually overloaded) 4100. This was with about 2K in the garage, which lightened the payload somewhat. IMO your GMC is more than capable of handling any Heartland product. I know without a doubt that you drive train will handle it. It's just a numbers game.

 

[richiek]

The 6,892 figure is the number from GM's spec page on that model (to be fair though while it didn't specify between DRW and SRW), 7,646 is from the fifthwheelst.com but that number was for a 4x2; thats why I used the 8k figure just to adjust for the 4x4.

 

[jmgratz]

The 6,892 figure is the number from GM's spec page on that model (to be fair though while it didn't specify between DRW and SRW), 7,646 is from the fifthwheelst.com but that number was for a 4x2; thats why I used the 8k figure just to adjust for the 4x4.

Most of the stats I have seen usually the 4x4 has a lower than 4x2 carrying capacity due to the extra weight of the 4x4 gears etc.

 

[danemayer]

The 6,892 figure is the number from GM's spec page on that model (to be fair though while it didn't specify between DRW and SRW), 7,646 is from the fifthwheelst.com but that number was for a 4x2; thats why I used the 8k figure just to adjust for the 4x4.

Ok, so when you use the RVTowcheck calculator, you're putting in 13,005 GVWR for the truck, and a curb weight of 8,000. That leaves you a payload of 5,005 lbs. You're probably marking the checkbox for the hitch, adding some weight for gear, and more for weight of driver and passenger. That likely reduces the available payload to less than 4,500 lbs.

At 25%, the 18,000 GVWR of the trailer puts 4,500 lbs pin weight on the hitch. Since you've already reduced available payload below 4,500, at 25% you'd be exceeding available payload.

The calculator then reduces the towing capability below 18,000 to show you the max you can tow without exceeding your available payload.

The purpose of calculating this way is to highlight the payload issue, which is usually overlooked.

Pin weight varies quite a bit, especially with toy haulers. So 25% is probably a worst case figure. Also, if you move some of your gear from the truck to the garage, you'll have more available payload.

 

[avvidclif]

Several people seem confused about GVWR, GCVWR, and a few other terms.

For the RV:
GVWR = 18k that is the maximum allowed weight of the trailer by itself, with ~15k shipping you can load up to 3k of "stuff" to include battery(s), water, and propane.
For the TV:
GVWR: The max the truck can weigh ready to drive down the road. This includes pin weight from the RV.
GCVWR: This is the max the entire rig can weigh, TV, RV, and passengers. Ready to drive.
Payload (or RAWR): This is the max that the rear axle can weigh.
Pin weight is figured as a percentage of the trailer weight. It does not add to the trailer GVWR nor subtract from it. Pin weights vary by trailer but most use 20% as an average number so for an 18k GVWR trailer use a pin weight of 3600 lbs. That is how much weight is being put on the TV's rear axle. It can go higher or lower, the scales will tell the truth.

For the above what is missing is the payload available for the TV. (It's on the drivers door plaque)

GCVWR = 30,500 Trailer GVWR 18k plus TV GVWR = 31,025. Slightly over if both loaded to the max.

GVWR = 13,025 TV @ 8k plus pin weight (20% of 18k (RV)) = 11,600 Safe there.

A newer model dually usually has over 4500 lbs of payload so you should be OK. I wouldn't have a problem with the combination posted depending on actual scale numbers.

 

[Doublegranch]

Not to argue but from the Ram Dealer...the Payload is not always equal to the GRAW....
example...my 2011 Ram Rear Axle gross is 6056 lbs however the payload is only 1870 max...thus I could never equal the Gross Rear Axle Wt.
If I could equal my rear axle wt, I would be upgrading to a new Sundance from my North Trail...but as it is the 1660 hitch wt and my 55 gal bed tank
puts me over my Trucks Payload.

 

[avvidclif]

Not to argue but from the Ram Dealer...the Payload is not always equal to the GRAW....
example...my 2011 Ram Rear Axle gross is 6056 lbs however the payload is only 1870 max...thus I could never equal the Gross Rear Axle Wt.
If I could equal my rear axle wt, I would be upgrading to a new Sundance from my North Trail...but as it is the 1660 hitch wt and my 55 gal bed tank
puts me over my Trucks Payload.

I never said it was equal. If you want to know what happened take the truck by itself to the scales with a full tank of fuel and ready to go camping then weigh it while sitting in it. The difference between the RAWR and the actual weight is the payload. You might be surprised. Whatever that number is should be the max pin weight.

 

[Doublegranch]

My truck was weighed a couple of weeks ago...
Scale....................Gross wt
3660 Rear axle......6010 .....scale wt with full tank of diesel and 55 bed tank full...
.........Payload........1840 per Ram
8640 ...truck wt,,,,..9600...including myself and two dogs

according to your numbers, I should be able to carry a payload of 2350 extra, including my both full tanks and myself and two dogs...
However the Ram Payload stats for my truck are 1840 lbs total. That is a difference of 510 lbs by your numbers...
The Sundance XLT hitch wt is 1660....putting the 2500 Ram diesel way over gross....
Per Ram dealer, the rear gross axle wt is not comparable with what you can put in the bed and cab.
While I can pull a gross of 20,000 lbs incl the truck, this is a far cry from what the payload will allow me to haul.
They reviewed my weight sheet and confirmed the payload is substantially lighter than what the Rear Axle is capable of hauling...

 

[campr-pete]

Hello All:

I wanted to reach out to the community in an attempt to have a few more eyes check the numbers on a new truck/fifth wheel matchup. Details below:


Road Warrior 425 5’er
GVWR: 18k lbs
Dry Weight: approx. 15k lbs


2015 GMC 3500 HD Crew Cab DRW Duramax 6.6 4x4
Curb Wt: 6,892 lbs/7,646 lbs (used 8k just to be safe)
GVWR: 13,025 lb.
GCWR: 30,500 lbs


Running the numbers on rvtowcheck.com it appears that with a 25% pin wt the max fifth wheel weight comes in at 16.5k lbs. (20,625 lbs at 20% pin wt.) which is just about my units dry weight and won’t allow for many (if any) future dirt toys. What am I doing wrong with these calcs? Or will the GMC DRW just not cut it for my 5’er?Thanks in advance for any thoughts/advice.

Richie

Just went through all of this with GM, I have a 2015 Chevy 3500hd drw , here is how it was explained to me, Take the gvwr subtract your curb weight and this equals your payload. So If you gvwr is 13,025 - the curb weight 7600lbs your payload is 5425lbs with my wife ,myself and the 2 dogs lounge chairs , grilles, etc I am towing a 4100 Cyclone 18,000lbs loaded and I am still 1300lbs under the payload or the gvwr. Gm stated that the rear in the 4 wheel drives are at the same weight rating as the 2wd. The numbers that I just gave you were actual weighed numbers no guessing. I do weight in the rear garage area which will make the hitch a little lighter.

 

[Bob&Patty]

To answer the question about 2WD and 4wd GCWR on a GM truck. A 4WD 3500HD is 500# less than a 2WD truck. MY 2013 3500HD 4WD, C/C DRW D/A L/B has a GCVW of 30500# same as the OP. Same truck with 2WD is 31000# GCVW. Your truck will have no problems with the CY.

 

[campr-pete]

Several people seem confused about GVWR, GCVWR, and a few other terms.

For the RV:
GVWR = 18k that is the maximum allowed weight of the trailer by itself, with ~15k shipping you can load up to 3k of "stuff" to include battery(s), water, and propane.
For the TV:
GVWR: The max the truck can weigh ready to drive down the road. This includes pin weight from the RV.
GCVWR: This is the max the entire rig can weigh, TV, RV, and passengers. Ready to drive.
Payload (or RAWR): This is the max that the rear axle can weigh.
Pin weight is figured as a percentage of the trailer weight. It does not add to the trailer GVWR nor subtract from it. Pin weights vary by trailer but most use 20% as an average number so for an 18k GVWR trailer use a pin weight of 3600 lbs. That is how much weight is being put on the TV's rear axle. It can go higher or lower, the scales will tell the truth.

For the above what is missing is the payload available for the TV. (It's on the drivers door plaque)

GCVWR = 30,500 Trailer GVWR 18k plus TV GVWR = 31,025. Slightly over if both loaded to the max.

GVWR = 13,025 TV @ 8k plus pin weight (20% of 18k (RV)) = 11,600 Safe there.

A newer model dually usually has over 4500 lbs of payload so you should be OK. I wouldn't have a problem with the combination posted depending on actual scale numbers.

Your math is including the pin weight twice, if the trailer weighs 18000lbs and the truck weighs 7500lbs your are now at 25500lbs so you have room for an additional 5000lbs. Pin weight on my cyclone4100 is right at 3050lbs if yours is similar you would have room for another 1950lbs for the passengers cargo etc so you will have plenty of capacity.

 

[avvidclif]

Your math is including the pin weight twice, if the trailer weighs 18000lbs and the truck weighs 7500lbs your are now at 25500lbs so you have room for an additional 5000lbs. Pin weight on my cyclone4100 is right at 3050lbs if yours is similar you would have room for another 1950lbs for the passengers cargo etc so you will have plenty of capacity.

Nope, you have to use the GVWR of the Truck and Trailer. You can't use actual on one and max on the other.

 

[DW_Gray]

Hello All:

I wanted to reach out to the community in an attempt to have a few more eyes check the numbers on a new truck/fifth wheel matchup. Details below:


Road Warrior 425 5’er
GVWR: 18k lbs
Dry Weight: approx. 15k lbs


2015 GMC 3500 HD Crew Cab DRW Duramax 6.6 4x4
Curb Wt: 6,892 lbs/7,646 lbs (used 8k just to be safe)
GVWR: 13,025 lb.
GCWR: 30,500 lbs


Running the numbers on rvtowcheck.com it appears that with a 25% pin wt the max fifth wheel weight comes in at 16.5k lbs. (20,625 lbs at 20% pin wt.) which is just about my units dry weight and won’t allow for many (if any) future dirt toys. What am I doing wrong with these calcs? Or will the GMC DRW just not cut it for my 5’er?Thanks in advance for any thoughts/advice.

Richie

Getting back to the OP: I'm not sure where you're going wrong. From my standpoint, I'd like your feedback as to where did I go wrong in the RV Tow Check instructions page.