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  1. #21
    Site Sponsor Crazybanshee's Avatar
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    The pin box is rated at 21,000 lbs so i am fine with the numbers. It has the 7,000 lbs axles so I am 4700 lbs under ratings.
    If I park the RZR into the left corner I can get a 100cc quad next to it and the stand two Banshees up with the tires against the ramp door
    2007 Volvo 780 VNL Trailersaver Hitch
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    3 Yamaha Banshee's 2-Honda 400 EX's
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  2. #22
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    My 2019 351M came w a sheet from the factory giving the pin and gross weight of the trailer w the installed options (which included the generator and 3rd AC). It was within a 100lbs at the scale

  3. #23
    Fireside Member JessJoe4168's Avatar
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    You can calculate the pin weight transfer for any mass by proportioning the center of gravity of the mass and the distance to the pin
    This applies to loads between the pin and the axle centerlines
    Loading behind the axles unloads the pin by the same amount as the increase in axle weight beyond the mass weight

  4. #24
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    Quote Originally Posted by LMychajluk View Post
    Yes, I intentionally worded it to try to focus the discussion on how to estimate the pin weight, and not turn it into another 'which truck do I need' thread. So, if I could rephrase my original question to be less vague - 'How do I most accurately estimate the max pin weight of a 5th wheel toy hauler?'. I don't think that's vague, though I understand it may not be easy question to answer. If it helps, assume I have a dually, but also want to haul around some anvils for my blacksmithing hobby in the bed of the truck.

    And FWIW, I have a SRW 1-ton truck currently on order. This truck will also be a daily driver, my only 4 wheeled vehicle capable of being driven on public roadways, a not a dedicated tow vehicle, and for various reasons that I won't get into detail here about, a dually is not currently an option for me. But at this point (and I am fully aware of this), the truck will limit my selection of trailers, not the other way around. I am not getting into a dually, and without doing so, there is not much I can or am willing to do to increase payload beyond the truck's current configuration. There are a few Toy Haulers I'm looking at, both from GD and other brands (some of which are significantly lighter than the Momentums...). Some of the options I'm considering are well within the limits I've established, and some are pushing those limits a bit, and I'm trying to make an educated decision on which I can comfortably and safely tow based on the info I have.

    The problem I'm running into is that the info published by the RV manufacturers is almost useless - I can't spec out a truck based on that info without grossly overestimating my needs. There also doesn't seem to be any way to get a valid estimate on the pin weight at GVWR based on any readily available information, and that can change based on how the trailer is loaded, pin height, and other factors as well. And using GVWR as the 'worst case scenario' isn't really valid, either - one can just as easily blow by that limit as well. BTW, the truck manufacturer's aren't any better - Ford's towing guide, for instance, claims you should estimate 15% of the trailer weight for 5th wheels, so if I use their numbers, I'm golden. Some on the internet say to estimate 25%, and if I go by that, I think I may have already killed myself and anyone in a 1/2 mile radius. On top of it all, any threads or posts you look at where someone asks for some real-world numbers on a specific model trailer, 95% of the answers are people jumping in with guestimates, not actual numbers, and are often based on different models and even entirely different model lines (e.g. - are pin weights really comparable between one guy's a 2-axle, 36' toy hauler and another guy's 3-axle, 42' travel trailers?), and that's not even getting into how the specific model was optioned and loaded.

    So, in my OP, as an 'estimate', I was wondering if I can use the percentage of dry tongue weight to UVW. I even found an online calculator that does this - http://www.towingplanner.com/Estimat...nWeightFromDry. But, even with the calculator, there's still the 'fudge factor', so even that calculator is not accurate. It also doesn't account for balance of the load and just assumes the same ratio, though I suspect that with a TH the percentage of pin weight will decrease as the trailer is loaded.

    Sorry if this sounded too much like a rant...
    This method will give a somewhat useful answer, but will not be exact. It all depends on what weight is loaded and where relative to the center of mass of the trailer. Pin weight could go up or down. I'd calculate it this way and if it's in 20-25% range, I'd feel pretty good about it within +/- 3% or so. JMO. Good luck!!

  5. #25
    Fireside Member JessJoe4168's Avatar
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    I would use the 20 -25% as well for ballpark if
    The example I gave would be useful for adding a component like a generator
    Two thoughts
    You will not know the side to side weight distribution
    If you are not running level, for calculation purposes, the assumed centerline of the tandem moves accordingly

  6. #26
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    It definitely is possible to estimate the impact of any weight change to the overall pin weight. All you need is the baseline weight, the location of the weight to be added, and the actual amount of weight to be added. I built a spreadsheet for my 381M to do just this.

    The theory behind this is straightforward. Not to get too much into the details, but when you add a weight to the trailer a new static balance will be established. By looking at the torques around the axles and the pin it is possible to calculate the impact on the pin weight and axle weight. My spreadsheet has entries to compute the impact of adding fuel, water, waste, or general cargo to the RV. Here are some examples for my particular unit:

    Configuration as delivered:
    - Total weight 15,084 pounds
    - Pin weight 2,650 pounds, 17.6%

    Impact to the base configuration of adding 1,000 pounds to the garage (in my case an ATV and motorcycle:
    - Total weight 16,084 (Up by 1,000 pounds)
    - Pin weight 2,247 (dropped by 403 pounds), 14.0%
    Notice the pin weight and the percentage dropped because the weight is behind the axles.

    Impact to the base configuration of filling the two fresh water tanks (104 gallons basically over the axles, 52 gallons slightly behind the axles)
    - Total weight 16,385 pounds (Up by 1,301 pounds)
    - Pin weight 2,635 (down by 15 pounds), 16.1%
    Adding a lot of weight here did not change the pin weight because the additional weight is mostly over the axles.

    Impact to the base configuration of traveling with full main gray and black tanks (each tank is 52 gallons about 12 feet in front of the axles)
    - Total weight 15,591 (Up by 867 pounds)
    - Pin weight 3,036 (up by 386 pounds), 19.0%
    This configuration adds a high percentage to the pin weight because the weight is well ahead of the axles.

    To check this with real world data and to answer your question about what the total pin weight could be, here are the measured values from my typical load including an ATV, motorcycle, groceries, the washer and dryer I added, tools, and so on. This is from a CAT scale:
    - Total weight 18,700 pounds (Up 3,616 pounds over my base configuration)
    - Pin Weight 3,060 (Up 410 pounds from my base configuration), 16.4%.
    Notice that adding 3,616 pounds of total weight only added 410 pounds to the pin, so about 11% of the additional weight went to the pin and 89% to the axles. This is why the rules of thumb for a toyhauler about how much the pin weight changes for a total weight change don't give accurate answers.

    I could try to make a very unbalanced load by taking my typical load and removing the ATV and motorcycle and also traveling with full waste tanks. This would increase my pin weight quite a bit:
    - Total weight 18,387 (down 313 from my typical configuration)
    - Pin weight 3,929 (up 869 from my typical configuration), 21.4%
    However, this is not a very realistic scenario for me. Given this is a toyhauler, I typically keep my toys in it for traveling and I never travel far with anything but empty waste tanks.

    Rather than using the rule of thumb of saying the maximum pin weight is 20-25% of the total weight I think you are better estimating the realistic total pin weight can increase by up to 11% of the total cargo carrying capacity. I showed in the last scenario that can change with your loading, but it should give a better answer than just taking a percentage of the total trailer weight.

    P.S. I expect to get many comments about needing more pin weight for a stable tow, what happens when you put every tool you own in the front cargo bay, and many other scenarios poking holes at the above. My experience from 18 months towing with my F-350 SRW is it is a smooth and stable tow, no issues with stability from winds or passing trucks, and easy to load without worrying about too much pin weight.

  7. #27
    Fireside Member JessJoe4168's Avatar
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    These calculations are all very useful. Especially for purchasing decisions
    But double check at the scale for verification and peace of mind

  8. #28
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    I agree you can use these as a guideline but the final judge is the CAT scale.

    I included my typical configuration that was measured on a CAT scale and also verified the calculations using a CAT scale. I went to the scale and weighed the unit, then unloaded the ATV and Motorcycle, weighed the unit again, then dumped the fresh water, and then weighed a final time. I didn't verify the waste tanks since that involves a lot more work to know the accurate fill level.

    I would also add that these numbers are for my tank layout and garage size. Different size garages will have different impacts as will differences in the tank layouts.

  9. #29
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    Quote Originally Posted by BobKilmer View Post
    ... Here are some examples for my particular unit...
    Wow, @BobKilmer! If I had those kinds of detailed examples for the 351M, I may be waving some money at a dealer already. Based on your '11% of CCC' estimate, the 351M would be ~3250# pin weight - well within my comfort zone. But you almost have me thinking about the 381M now, just because I'd be perfectly comfortable with the numbers as you've presented them. Thanks very much for that detailed post!

  10. #30
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    Quote Originally Posted by LMychajluk View Post
    Wow, @BobKilmer! If I had those kinds of detailed examples for the 351M, I may be waving some money at a dealer already. Based on your '11% of CCC' estimate, the 351M would be ~3250# pin weight - well within my comfort zone. But you almost have me thinking about the 381M now, just because I'd be perfectly comfortable with the numbers as you've presented them. Thanks very much for that detailed post!
    You're welcome, I am glad you found the data helpful. Hopefully someone with a 351M can provide their actual numbers as well. I actually planned on buying the 351M but switched to the 381M at the last minute.

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