Trailer Life Directory Open Roads Forum: Difference in Tow ratings between TT and Fifth Wheels
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Open Roads Forum  >  Towing

 > Difference in Tow ratings between TT and Fifth Wheels

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Posted: 03/16/10 10:21pm Link  |  Print  |  Notify Moderator

I was recently looking into changing from a 33ft travel trailer to a fifth wheel. I have a 2005 6.6L turbo Diesel GMC Sierra 2500HD. I know the towing capacity of the vehicle is 12,000lbs. I recently saw a newer truck and in the specs it had a different weight for a ball mount hitch compared to a fifth Wheel hookup, with the fifth wheel number being substantially higher by about 2300lbs. Is this a given between the different hitches? I would like to know so I can get my limitations on what kind of 5th wheel I can purchase. Thanks for any help out there. It would be greatly appreciated.


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Posted: 03/16/10 11:02pm Link  |  Print  |  Notify Moderator


The tow ratings from some manufactures can be misleading. What they do is take the GCVWR of both vehciles, subtract the empty weight of the truck and 1 driver (154 pounds) then "Claim" you can tow that much weight.

However there is one more restriction. Lets say you select a fifth wheel that is 10,000 pounds. Well within the advertised weight rating for your 2500 series truck. Now you plan on installing a 200 pound hitch in the truck bed, and that brings up the "Empty truck weight" by 200 pounds. Also you might plan on taking along the family, grandkids or whoever? That will add about 300 - 500 pounds to the truck too.

If you have a regular cab, 6L gas engine, then you still have a lot of cargo rating left. But if you decided to add a 400 pound heavier diesel engine, 200 pounds of crome and electric seats, 400 pound crewcab option, then your empty weight goes way up, beond that regular cab with only a 154 pound driver and lightweight gas engine.

So the best thing to do at this point is go to a scale. Find your GVWR on the door of your truck. Subtract the empty weight from the GVWR, and you will find the cargo rating. Lets say that you can carry 2,200 pounds. Your passengers, dog, cooler, and other things in the truck come to 200 pounds. This leaves 2,000 pounds.

If you are towing a 8,000 pound fifth wheel with 25% (2,000) pounds on the hitch, and installed a 200 pound hitch, you will be 200 pounds over the GVWR for your truck. So in reality, unless you have a regular cab, or tow a trailer with a especially light weight hitch weight, then you can only tow about 8,000 pound fifth wheel.

For a conventional trailer, then your hitch weight will only be about 10% to 13%. So a 10,000 pound conventional trailer might have 1,300 pounds on the hitch, the equalizer hitch might be 75 pounds, leaving 600 pounds before exceeding the GVWR of your truck.

Back to your original question.

Why do the manufactures rate the trucks to tow more with a fifth wheel than for a conventional trailer?

The manufactures do stability tests with their trucks. They hitch up a trailer, and tow it on a closed track with many sharp curves. They find that going over a certain weight the trucks can become unstable. But with a fifth wheel, the trucks stay much more stable.

So the manufactures are stating that the truck should be stable with a 10,000 pound conventional trailer, or a 15,000 pound fifth wheel.

I guess they found a fifth wheel that has a very light hitch weight, when they conduct those tests. My guess is they use a cargo trailer full of cement blocks to do the tests, not a travel trailer or RV of any sort. A cargo trailer with a steel flatbed and a couple of 3,000 pound cement blocks can be built for about $2,000, while a RV would be over $20,000.

It is sad every time I answer this question for someone with a 2500 series truck. To explain it "Can" tow a 14,000 pound fifth wheel, but only if you find one with a 1,400 pound hitch weight. And the RV fifth wheels with a 1,400 pound hitch weight is only going to have a GVWR of about 7,500 to 8,500 pounds.

I suggested to someone in Ford's upper management that they discontinue the F-250 supercab and crewcab diesels, because the cargo rating on a F-250 4 wheel drive crewcab diesel was only 850 pounds before 2005. (66% of Ford's truck sales where diesels, they would never drop the diesel, so they did something else) In 2005, Ford started rating it's trucks for a higher GVWR when heavy options are installed. So a 4 WD crewcab can now carry 3,000 pounds, and actually tow a fifth wheel with a 2,200 pound hitch, and passengers.

So what is required to safely tow a 14,000 pound fifth wheel RV with a 2,800 to 3,000 pound hitch weight? A dually F-350 can carry 5,500 pounds. The F-350 SRW can carry about 4,000 pounds, so if you are not taking along a lot of people in the truck, it will work fine too.

As for your truck, I think you will find that the towing limit for a fifth wheel will be limited to only about 8,000 - 10,000 pounds, due to the heavy hitch weight.

There are exceptions. Check out this RV brand, it has the water tanks by the axles, so the hitch weight is not nearly as high as most RV's.

Good Luck,



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Posted: 03/16/10 11:24pm Link  |  Print  |  Notify Moderator

LOL ok now for the real world. My trailer weighs loaded 12000 lbs and has a hitch weight of 2300 lbs. I am with in all my limits. Now when we hit the road for a couple months then my trailers weight jumps up to 12500 lbs and I am around 300 lbs over my GVWR but well under the axle and tire ratings. As it is it is rock solid with no safety or handling issues. Now if I were to go heavier then I don't know it would be as comfortable towing cross country. I don't know of many 3/4 ton trucks which could not handle a 2500 lb pin weight. If you are worried about it then just beef up the suspension with air bags or super springs and you have a 1 ton. Only problem is the door sticker won't say so. But that is a problem for a few.

Definitly check out the 5th wheel cause you will not go back to a TT. Although bigger they tow a lot nicer and are more stable. The reason for the difference is a lot more weight is over the trucks axle instead of the the bumper.

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Posted: 03/17/10 07:40am Link  |  Print  |  Notify Moderator

m1c43 wrote:

I would like to know so I can get my limitations on what kind of 5th wheel I can purchase. Thanks for any help out there. It would be greatly appreciated. I have a 2005 6.6L turbo Diesel GMC Sierra 2500HD

I believe the 12000 lb figure is the max for a TT (bumper pull). According to Edmunds the '06 2500 Dmax/A can tow a 5er up to 15000-15500 lbs depending on cab/2wd vs 4wd/etc.

Gm gives your 2500 truck a 6084 RAWR/tire capacity for carrying weights from a 5er which sets over the trucks rear axle. According to GM weight calculator most 2500 trucks rear axle, with the Dmax, weighs 2670 lbs which leaves you with approx a 2600-2800 lb for a pin weight. That will be a max axle/tire cap number and I would stay under them.

Now look at 5er that weighs under 15000 lbs (or whatever GMs tow rating is) with a WET pin weight (not a manufactures dry pin weight)under 2600-2800 lbs.

Weighing a trucks front and rear axle weights is necessary for finding max axle/tire loads.

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Posted: 03/17/10 08:41am Link  |  Print  |  Notify Moderator

It's NOT a given and should only be TAKEN when it's published. Tow ratings tell the user at what weight the manufacturer will no longer honor the tow vehicles warranty on weight related issues. Good luck / Skip

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Posted: 03/17/10 08:53am Link  |  Print  |  Notify Moderator

"ANYBODY" look a the hitch that GM supplies for a ball mount? you will see the max limit is 12K lbs, hence the 12K rating vs 14500 or what ever it is for a 5w. GM, Ford etal have had this issue going back some 20+yrs! Take a truck with a smaller than 12K rating, ie a typ half ton, and the 5w/ball mount rating is equal. Then, if you call GM and you truck does NOT HAVE a trailer hitch pkg from the factory, they tell you the tow rating is 4500 lbs or there abouts for a dmax, as that is the bumper rating.

Now for reality, as mentioned, get your rig weighed, figure out how much wt you can put on the RA before going over it capacity. I would recomend you keep this amount to no more than 5500 of the 6100 lbs rating. Otherwise you will have issues with bottoming out going over, thru speed bumps, dips in the road etc.

There were also many many folks when GM first came out with the DA combo that bought 12-14K trailers, pulled like a banshee, BUT, almost ALL with 2500's were trading in there rigs for 3500 duallies due to bottom out issues, and a slightly overloaded RA.

Remember, 20-25% of the total trailer wt will be hitch wt, to be carried by the truck. So a 12K trailer will have upwards of 3000lbs on the RA. TOO MUCH! empty the RA will be about 2200-2400 lbs on it, leaving you with about 3500 to play with, including hitch, people etc. A ball mount on the other hand, will have 10-15% of the total in HW< giving you a max with no issues usually of 14K lbs behind the rig.


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Posted: 03/19/10 09:48am Link  |  Print  |  Notify Moderator

Keep in mind that the 2500 shares it's frame and rear axle with the 3500. If you go with a higher weight rated tire and two more leafs in the rear spring pack, you have, essentially, a 3500.

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Posted: 03/19/10 10:24am Link  |  Print  |  Notify Moderator

Some people believe in 'magic spring dust' (changed in capacity without changing the vehicle, MY changes, marketing, ect), some believe in the sticker in the door, some believe in the mechancial systems (brakes, axle, frame, ect) being identical and others just do as they wish... You will never get a straight answer on this as there is none (legally vs warranty, ect). My .02 is to stay under GAWR & tire ratings....

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Posted: 03/20/10 12:58am Link  |  Print  |  Notify Moderator

m1c43 wrote:

I recently saw a newer truck and in the specs it had a different weight for a ball mount hitch compared to a fifth Wheel hookup, with the fifth wheel number being substantially higher by about 2300lbs. Is this a given between the different hitches? I would like to know so I can get my limitations on what kind of 5th wheel I can purchase. Thanks for any help out there. It would be greatly appreciated.

With any given truck, you CAN safely tow a heavier fifth wheel trailer than you can a tag-hitch (bumper pull) travel trailer. The sole reason for that is that a fifth wheel hitch is mounted above, and usually an inch or two in front, of the rear axle. This means that the truck is no longer a lever with the rear axle as it's fulcrum. The weight of the trailer is better distributed to both axles (better than any weight distributing hitch can accomplish), and the front end doesn't get so light that steering ability is affected. A tag-hitch can create a lot more "wagging" in the truck than a fifth wheel will, also, in windy situations or when a semi meets or passes. The fifth wheel hitch is a much more secure connection for a larger trailer than a ball mount could ever be.

With all of that said, make sure you calculate the permissible size of your trailer before you buy one. And, when choosing a trailer, use the GVWR of the trailer, and not the dry weight (UL Weight), because you probably will load it to the max when you camp with it. My fifth wheel weighs 14,800 (trailer GVWR is 14,999.) I weigh-in at least once every six months to be sure that we're still good-to-go.

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Posted: 03/20/10 06:42am Link  |  Print  |  Notify Moderator

atvanish, there's no need to "believe in" magic spring dust, whatever that is. The GM parts catalog tells us what we need to know: the 2500HD and the 3500 are virtually the same truck. They use the same rear axle, frame, brakes, and most other parts. The principal differences are the tires and springs. Change those, and you can have a short bed 3500--something GM doesn't offer.

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