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A Weighty Issue


WaywardWaylander

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In my research, I've been obsessing over weight. No, not MY weight (different issue, wrong forum), but weights and weight ratings of 5th wheels and the payload & towing capacity of trucks. I've been doing some math and wanted to run some numbers by the members here to make sure I'm not out in left field.
To set expectations, I'm the kind of guy who likes to over-engineer things. I like to design in cushion, or buffer, into things to keep away from problems and stay within safety margins. I don't like to take chances with things that are important to me. This tendency definitely applies in this case.
I'd like to keep this as a focused academic discussion. I don't want this to go down the rat-hole of MDT vs HDT; I'm just interested in the trade-offs between towing capacity and payload.
For this discussion, let's take the following specs from an example luxury 5th wheel:
Shipping Weight: 13140
Carry Capacity:   3745
Hitch:            2885
GVWR:            16885
To make the math a little easier, we'll round up the hitch and GVWR to 3000 & 17000, respectively. This tells me I need a truck that can tow at least 17,000 pounds and has an available payload (after passengers, fuel, etc) of 3,000 pounds.
For this discussion, let's consider the following two trucks. They are both crew cab (for personal reasons) DRW models. As configured, their maximum ratings are as follows:
TRUCK 1:
   5th Wheel Max Trailer Weight: 24000
   Max Payload:                   6870
   Curb Weight:                   7800
   GCWR:                         32100


TRUCK 2:
   5th Wheel Max Trailer Weight: 31200
   Max Payload:                   5300
   Curb Weight:                   8600
   GCWR:                         40400
In addition, we'll assume 37.5 gallons of diesel fuel, for a weight of 281.25 pounds, and one adult and two kiddos, which we'll pin at 400 pounds total. That's 682 pounds (rounded up) of payload before we get to the hitch weight of the 5th wheel.
For the academic discussion, we now have the basic numbers we need. In my mind, I compare the trucks as follows:
TRUCK 1:

   5th Wheel Max Trailer Weight: 24000
   5th Wheel GVWR:               17000
   Delta:                         7000
   Cushion % (Delta/Max Rating):   29%

   Max Payload:                   6870
   5th Wheel Hitch Weight:        3000
   Fuel/Passengers:                682
   Delta:                         3188
   Cushion % (Delta/Max):          46%

   Total Combined Weight Max:    25482 (Trailer Max + passenger/fuel + truck curb weight)
   GCWR Cushion lbs:              5718
   GCWR Cushion %:                 18%

TRUCK 2:

   5th Wheel Max Trailer Weight: 31200
   5th Wheel GVWR:               17000
   Delta:                        14200
   Cushion % (Delta/Max Rating):   45%

   Max Payload:                   5300
   5th Wheel Hitch Weight:        3000
   Fuel/Passengers:                682
   Delta:                         1618
   Cushion % (Delta/Max):          30%
   
   Total Combined Weight Max:    25482 (Trailer Max + passenger/fuel + truck curb weight)
   GCWR Cushion lbs:             14118
   GCWR Cushion %:                 35%

Here are my takeaways from this comparison:

Truck 2 has a massive advantage when it comes to towing capacity and GCWR, obviously. However, given the GVWR of the trailer, the trailer isn't quite 55% of the towing capacity of the truck. Even with my conservative, safety-conscious approach, this seems like massive overkill. The trailer is just shy of 71% of the towing capacity of Truck 1, giving a 29% cushion in towing capacity. This seems more than adequate for a cushion.
Truck 1, then, has the advantage in payload. At a 46% and 3188 pound cushion, it seems a much better choice than Truck 2's 30% and 1618 pound cushion. This appeals to me because that extra 1570 pounds of Truck 1's payload would allow me to better outfit the truck with more things like auxiliary fuel tanks, tool boxes, beefier 5th Wheel hitch, and so on.
From this data, and from my perspective, it would seem that Truck 1 is the better choice. It has a very comfortable towing capacity cushion while offering better payload capacity. What concerns me is that I'm missing something in the towing capacity equation that matters, or that the 29%/7000 pound towing cushion isn't enough for some reason. Am I missing anything?
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For this discussion, let's take the following specs from an example luxury 5th wheel:

 


Shipping Weight: 13140
Carry Capacity:   3745
Hitch:            2885
GVWR:            16885

Two things I notice right away:

 

1) That shipping weight may not be the actual dry weight of the fifth wheel as it comes off the assembly line, unless this particular manufacturer weighs each and every rig before shipping and puts that number on the tag you'll find inside the rig somewhere.

 

While *some* manufacturers do this, most don't. So, unless you know for a fact that the rig was weighed before leaving the manufacturing plant, what you likely have in that shipping weight is the weight of the basic unit before options are added.

 

2) By the same token, the hitch weight is the dry hitch weight, not what it will be once you've loaded the fifth wheel up with propane, water, and all your supplies. Since hitch weight can range from 20% to 25% of the fifth wheel's GVWR, you're looking at a possible loaded hitch weight of 3,377# to 4,221.

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Two things I notice right away:

 

1) That shipping weight may not be the actual dry weight of the fifth wheel as it comes off the assembly line, unless this particular manufacturer weighs each and every rig before shipping and puts that number on the tag you'll find inside the rig somewhere.

 

While *some* manufacturers do this, most don't. So, unless you know for a fact that the rig was weighed before leaving the manufacturing plant, what you likely have in that shipping weight is the weight of the basic unit before options are added.

 

2) By the same token, the hitch weight is the dry hitch weight, not what it will be once you've loaded the fifth wheel up with propane, water, and all your supplies. Since hitch weight can range from 20% to 25% of the fifth wheel's GVWR, you're looking at a possible loaded hitch weight of 3,377# to 4,221.

 

Understood. The numbers can be updated later to reflect reality. The point of the post and the question is the different between towing capacity and payload ratings between the two trucks.

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I see no consideration given to Gross Combined Weight Ratings (GCWR) of either truck. Personally I would not focus on the "max trailer weight ratings", Instead use the GCWR because that max weight rating is with just a driver and a small amount of fuel and no cargo. I realize you have factored in both passengers and fuel but using GCWR is just much easier. Of course you must consider the trucks GVWR (primarily the rear axle rating) to make sure you can carry 20-25% of the trailer weight. My last fiver weighed in at 19,000 and had a pin of 4500 after being loaded. I pulled with a MDT so pin weight was not an issue but I am not sure too may of the 1 tons on the market could carry that much.

 

Obviously you don't want to exceed the max trailer weight ratings but for your safety margin analysis the GCWR would be as better assessment IMHO.

 

Lenp

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I see no consideration given to Gross Combined Weight Ratings (GCWR) of either truck. Personally I would not focus on the "max trailer weight ratings", Instead use the GCWR because that max weight rating is with just a driver and a small amount of fuel and no cargo. I realize you have factored in both passengers and fuel but using GCWR is just much easier. Of course you must consider the trucks GVWR (primarily the rear axle rating) to make sure you can carry 20-25% of the trailer weight. My last fiver weighed in at 19,000 and had a pin of 4500 after being loaded. I pulled with a MDT so pin weight was not an issue but I am not sure too may of the 1 tons on the market could carry that much.

 

Obviously you don't want to exceed the max trailer weight ratings but for your safety margin analysis the GCWR would be as better assessment IMHO.

 

Lenp

 

Added.

 

While it adds some depth to the argument (that Truck 1 would only have an 18% GCWR cushion vs Truck 2's 35%), the fact remains that Truck 1 still HAS a cushion, and a nearly 20% cushion at that, while still offering better payload capacity than truck 2, regardless of Truck 2's massive advantage in towing & GCWR.

 

My worry with Truck 2 is not having a comfortable cushion for adding things such as auxiliary fuel tanks (more fuel weight), beefy 5th wheel hitch and so on with the potential hitch weight of the RV.

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As already stated, if you're looking at dry weights you might need to add 2k or so.

 

I'm not factoring around dry weight. I'm factoring around the GVWR of the trailer (dry weight + carry capacity), rounded up (Shipping Weight 13140 + Carry Capacity 3745 = 16,885, rounded up to 17,000). I'm being very conservative here, planning for worst case, with the trailer fully loaded.

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Just went thru simmular exercise and you will probably find that truck #2 is getting towing capacity by increasing the rear end ratio. If you compare the trucks with the same ratio's (guessing truck 2 has 3 different ratio options) you will find them closer in comparrison. I did not see any differances in braking capacities with the increased towing capacity. My choice would be truck #1

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Just went thru simmular exercise and you will probably find that truck #2 is getting towing capacity by increasing the rear end ratio. If you compare the trucks with the same ratio's (guessing truck 2 has 3 different ratio options) you will find them closer in comparrison. I did not see any differances in braking capacities with the increased towing capacity. My choice would be truck #1

 

X2 You can if you like, take truck 1 back to the dealer and have them install a 4:30 or 4:10 rear end depending on the truck and then it would be equal to truck 2, you would have the best of both worlds.

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Just went thru simmular exercise and you will probably find that truck #2 is getting towing capacity by increasing the rear end ratio. If you compare the trucks with the same ratio's (guessing truck 2 has 3 different ratio options) you will find them closer in comparrison.

X2 You can if you like, take truck 1 back to the dealer and have them install a 4:30 or 4:10 rear end depending on the truck and then it would be equal to truck 2, you would have the best of both worlds.

 

This is a perfect segue into the reveal of the two trucks I'm comparing.
But first, I had to update the stats on Truck 1. I read the wrong line on the specification sheet; it actually has more payload capacity than originally indicated. This gives Truck 1 an even more impressive payload advantage over the Truck 2.
Now for the reveal. The specifications I used for this exercise are available on the Ford Super Duty Brochures & Guides page. Just click the "Download PDF Now" link under "Specs Brochure". From this, I used the specs for the following two trucks:
Truck 1: F350 Crew Cab DWR Diesel 4x2
Truck 2: F450 (Crew Cab DWR Diesel 4x4)
To address Dale G's and jimmac28's comments above, these two configurations are only available from the factory with one rear gear ratio each: 3:73 for the F350 CC DRW 4x2, 4:30 for the F450. I assume I could have the dealer swap out the gears, but if the guide is any indication, this would result in a drop in payload capacity, which wasn't the point of this exercise.
If I were willing to let go some payload for extra towing cushion, I would probably opt for the F350 CC DWR Diesel 4x4 with the 4:30 rear ratio. This would drop my payload by 410 pounds, but increase my 5th Wheel towing to 26,500 and GCWR to 35,000. Not sure I need that trade-off, though. I'll have to give it more thought. Academically, of course...
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This is a perfect segue into the reveal of the two trucks I'm comparing.
But first, I had to update the stats on Truck 1. I read the wrong line on the specification sheet; it actually has more payload capacity than originally indicated. This gives Truck 1 an even more impressive payload advantage over the Truck 2.
Now for the reveal. The specifications I used for this exercise are available on the Ford Super Duty Brochures & Guides page. Just click the "Download PDF Now" link under "Specs Brochure". From this, I used the specs for the following two trucks:
Truck 1: F350 Crew Cab DWR Diesel 4x2
Truck 2: F450 (Crew Cab DWR Diesel 4x4)
To address Dale G's and jimmac28's comments above, these two configurations are only available from the factory with one rear gear ratio each: 3:73 for the F350 CC DRW 4x2, 4:30 for the F450. I assume I could have the dealer swap out the gears, but if the guide is any indication, this would result in a drop in payload capacity, which wasn't the point of this exercise.
If I were willing to let go some payload for extra towing cushion, I would probably opt for the F350 CC DWR Diesel 4x4 with the 4:30 rear ratio. This would drop my payload by 410 pounds, but increase my 5th Wheel towing to 26,500 and GCWR to 35,000. Not sure I need that trade-off, though. I'll have to give it more thought. Academically, of course...

 

 

Well I though you were comparing an F350 to a Ram 3500, a F450 is not apples to apples. The F450 has a heaver axle a Dana S 110 rated at 14700 lb, to a Dana 80 on the F350 rated at 11000. The F450 has bigger brakes larger tires 19.5 in, and its one bad truck, understand that the ratings I'm giving are manufacture ratings not Fords.

 

I tow a Mobile Suite at 18000 lb with a F350 Dually two wheel drive like your looking at and love it.

 

Ford and GM for some reason do not offer the taller rear axle on there F350 and 3500, thats why I suggested you getting the 4:30, It cost about $1500 to install last I checked.

 

The F450 is a heaver truck and has the same engine as the F350, thats why the drop in payload, so if you installed the 4:30 in the F350 that might be the ticket. Not that Ford would like it, you can see the marketing problem.

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The F450 is a heaver truck and has the same engine as the F350, thats why the drop in payload, so if you installed the 4:30 in the F350 that might be the ticket. Not that Ford would like it, you can see the marketing problem.

 

This was one of the things, besides the academic exercise, that I was trying to prove out to myself. Hit the nail squarely on the head.

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This is a perfect segue into the reveal of the two trucks I'm comparing.

 

But first, I had to update the stats on Truck 1. I read the wrong line on the specification sheet; it actually has more payload capacity than originally indicated. This gives Truck 1 an even more impressive payload advantage over the Truck 2.

 

Now for the reveal. The specifications I used for this exercise are available on the Ford Super Duty Brochures & Guides page. Just click the "Download PDF Now" link under "Specs Brochure". From this, I used the specs for the following two trucks:

 

Truck 1: F350 Crew Cab DWR Diesel 4x2

Truck 2: F450 (Crew Cab DWR Diesel 4x4)

 

To address Dale G's and jimmac28's comments above, these two configurations are only available from the factory with one rear gear ratio each: 3:73 for the F350 CC DRW 4x2, 4:30 for the F450. I assume I could have the dealer swap out the gears, but if the guide is any indication, this would result in a drop in payload capacity, which wasn't the point of this exercise.

 

If I were willing to let go some payload for extra towing cushion, I would probably opt for the F350 CC DWR Diesel 4x4 with the 4:30 rear ratio. This would drop my payload by 410 pounds, but increase my 5th Wheel towing to 26,500 and GCWR to 35,000. Not sure I need that trade-off, though. I'll have to give it more thought. Academically, of course...

I use the F-350 4x4 it is a 2016 diesel with the 535 max tow package. This package gives you the F-450 wide track front axle and increases towing to 31,200/26,000 fifth wheel. If you are looking at the ford tow charts the figures you quoted are with this package.

The 35,000 number you used in your chart is for a truck with the 4:30 diff and the 26,000 fifth wheel weight is not a true towing rate. Ford states this number because this is the largest hitch that they offer. I tow a 40' 26,432 lbs fifth wheel with this truck I use a 30k Comfort Ride hitch and have no problem what's so ever. Stopping is always my number one concern, I have the triple Moryde with oversize anti lock disc brakes which will drag my truck to a stop instead of pushing me through a stop light.

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Yup, I noticed this in the brochure. There is a footnote in that column. For this exercise, though, it didn't have a significant effect on the comparison, from my perspective, but it is still good to know.

The big difference is in order to get to that GCW the truck has to be a crew cab long bed 4x4 dully. The heavy tow package is only a 400.00 upgrade but you basically get a 450 at a 350 price. I just put mine up for sale due to ordering a new 45' RV that weights 37k so we are going to the HDT which my wife has reservations about.

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I use the F-350 4x4 it is a 2016 diesel with the 535 max tow package. This package gives you the F-450 wide track front axle and increases towing to 31,200/26,000 fifth wheel. If you are looking at the ford tow charts the figures you quoted are with this package.

The 35,000 number you used in your chart is for a truck with the 4:30 diff and the 26,000 fifth wheel weight is not a true towing rate. Ford states this number because this is the largest hitch that they offer. I tow a 40' 26,432 lbs fifth wheel with this truck I use a 30k Comfort Ride hitch and have no problem what's so ever. Stopping is always my number one concern, I have the triple Moryde with oversize anti lock disc brakes which will drag my truck to a stop instead of pushing me through a stop light.

Umm... but what happens if/when you lose the connection to those oversize disc brakes. One wire thru several connections and two electronic devices all of which are possible failure points. Then who is in charge, the 26,000 lb trailer or the 9000 lb tow vehicle?

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Umm... but what happens if/when you lose the connection to those oversize disc brakes. One wire thru several connections and two electronic devices all of which are possible failure points. Then who is in charge, the 26,000 lb trailer or the 9000 lb tow vehicle?

That is always the case. You have to balance the tradeoffs. Even my 24K HDT will feel my trailer if I don't have trailer brakes. My trailer weighs 28,300 lbs, though. I'd be more "concerned" about an emergency maneuver than losing the brakes. Or with wind gusts. Assuming you are careful about the brakes and check things at each stop - which should be about every two hours - the chances of losing brakes is not that great, IMO. But you do have to be alert.

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That is always the case. You have to balance the tradeoffs. Even my 24K HDT will feel my trailer if I don't have trailer brakes. My trailer weighs 28,300 lbs, though. I'd be more "concerned" about an emergency maneuver than losing the brakes. Or with wind gusts. Assuming you are careful about the brakes and check things at each stop - which should be about every two hours - the chances of losing brakes is not that great, IMO. But you do have to be alert.

I agree that the chances of losing trailer brakes are not that great but with a 26,000 lb trailer and a 9000 lb tow vehicle the results in certain situations could be catastrophic for him and anyone around him.

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I agree that the chances of losing trailer brakes are not that great but with a 26,000 lb trailer and a 9000 lb tow vehicle the results in certain situations could be catastrophic for him and anyone around him.

I'm not sure what you are saying....are you indicating that a Dodge 3500 or 5500 should not be towing those weights? They are speced for them, if set up right. Personally, I prefer the heavier truck but the Dodge 5500, for one, is pretty capable at the 25K or so level. Failure of equipment is always an issue....that one needs to mitigate as much as possible. But it can never be totally prevented. Simply look at commercial truck wrecks to see....Oh, and BTW, a commercial hauler of 60K lbs with a 20K truck is kinda lopsided in weights as well....

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Umm... but what happens if/when you lose the connection to those oversize disc brakes. One wire thru several connections and two electronic devices all of which are possible failure points. Then who is in charge, the 26,000 lb trailer or the 9000 lb tow vehicle?

Not a likely scenario, but it has happened, to me. In January, we were going through Tyler, Texas with our 21k toy hauler behind, when I noticed the trailer brakes weren't contributing to the whoa chores. Fortunately, we had a big enough truck so as to be able to proceed safely, at a reduced pace.

 

The brake controller was the culprit, and it said so on the screen. Next morning, on the way to the shop we'd called to fix it, it woke up and decided to make up for lost time. Smoked all six new tires, through the cords. No tires went flat, but you could see the air inside.

 

I'm getting a BluDot system.

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With electric brakes it takes just one wire failure to lose the trailer brakes. With hydraulic disc brakes, it takes just one line cut to lose the trailer brakes (happened to me).

 

Bottom line is the GCWR of a truck assumes that the trailer will supply its own brakes. With no trailer rake, a 9000 lb truck will have little stopping power with a 28,000 lb trailer behind.

 

There in lies a major benefit of an HDT with GVWR of 40,000 lbs or more. Enough braking for the truck and trailer.

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Except that the majority of the weight in a commercial trailer is on the pin i.e. the tow vehicle, see where the axles are on the trailer.

 

I've personally lost trailer brakes 3 different times in the past couple of years, once when the brake light switch went intermittent, once when the brake controller (top of the line Prodigy) malfunctioned and once when the plug to the trailer came out (my fault). I was really glad that I had a tow vehicle that was able to cope and that we weren't on one of those 3 mile 10% grades out west.

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I agree. I am planning on getting an HDT in the not to distant future. It may look funny pulling my little 28 footer, but then when I can upgrade I don't need to worry about truck capacity.

That is very smart. No more truck buying... :)

 

It is TRUE that you cannot have "too much truck". :)

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