Towing a travel trailer weight calculator - Page 2 - Escape Trailer Owners Community

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Old 10-30-2013, 12:59 PM   #11
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Originally Posted by TAfraser View Post
I have to believe that the vehicle manufacturer applies it's own safety margins when supplying it's tow and hitch ratings. Since we don't know what those safety margins are, is that the reason we add more, or is it that we just don't trust the manufacturer to do his part properly?
I think those are both essentially the same reason, and I suppose that is why some people add more margin. I think others add a margin because they are checking only the trailer weight limit (not GCWR, GAWR, GVWR...) and so they "want to be safe" without doing the work. Of course, they might just have a vehicle from a less trustworthy manufacturer...

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Originally Posted by TAfraser View Post
It sounds like your spreadsheet takes other safety issues into account. Care to share?
All I added is the distribution of load between the front and rear axles of the tug, and I don't have the cool "supply what you have" feature.

I have no idea how well this will work for others, but try this link to Google Drive and you can see my workbook of four spreadsheets: two for different configurations of someone's minivan and trailer, one showing scale readings and working out the pin position of Fran and Dave's Frontier/Escape rig, and one for Fran and Dave's rig. To play with it yourself, you could copy the desired sheet to your own Google Drive spreadsheet.

I have attached a PDF (readable) version of the workbook to this post; unfortunately, Excel files are not allowed as attachments, so no formulas (but they're visible in the Google Drive spreadsheet document).
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File Type: pdf Vehicle and trailer loading - sample.pdf (103.0 KB, 25 views)
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Old 10-30-2013, 01:09 PM   #12
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My hitch indicates 5000/500, and the Ridgeline is rated for 5000 lb of towing. The placard on the side of my 21 indicates a GVWR of 2090KG, which is 4607 lbs. Using 4500 lbs, the tongue weight (at 12% of trailer weight) would be 540 lbs, exceeding the hitch rating. Turning this around, applying the 12% rule to the hitch maximum gives me a towing capability of 4167 lbs. This time I'm below what the trailer will probably weigh when fully loaded. All these numbers are without applying the so called safety factor. Hopefully the manufactures apply an appropriate safety factor when publishing their numbers. BUT, after working in Metrology (calibrations of test equipment) for 26 years, manufacturers are more interested in sales then safety when advertising.
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Old 10-30-2013, 01:21 PM   #13
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Spreadsheet

Nice job with the spreadsheet Brian. Thank you
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Old 10-30-2013, 01:25 PM   #14
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Tom,
Do you have a Sherline t/w scale? that may help with your numbers.
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Old 10-30-2013, 02:40 PM   #15
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Nice job with the spreadsheet Brian. Thank you
You're welcome!

I was half-expecting something more like "what is that chicken scratch supposed to mean". Questions and comments are welcome, although if detailed might be best by e-mail (my address is registered with the forum).
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Old 10-30-2013, 02:54 PM   #16
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Originally Posted by TAfraser View Post
Using 4500 lbs, the tongue weight (at 12% of trailer weight) would be 540 lbs, exceeding the hitch rating. Turning this around, applying the 12% rule to the hitch maximum gives me a towing capability of 4167 lbs. This time I'm below what the trailer will probably weigh when fully loaded.
That makes sense. Some options:
  1. reduce trailer weight (carry less stuff)
  2. use lower tongue weight fraction (with suitable distribution, 12% should not be necessary; tow vehicle manufacturers usually assume 10%)
  3. check if the Ridgeline allows a higher tongue weight if a weight-distribution system is used (commonly true for other vehicles, especially pickup trucks)

Since the online calculator ignores weight distribution, it ignores weight-distributing hitch (WDH) systems. My spreadsheet ignores WDH as well.

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Originally Posted by TAfraser View Post
... manufacturers are more interested in sales then safety when advertising.
In some cases (especially the "Big 3" pickup manufacturers") that seems to be true, but I think the advertised numbers are more misleading by omission (of all the other limits) than by exaggeration (of the basic trailer weight limit).
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Old 10-30-2013, 03:05 PM   #17
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Honda recommends against the use of weight distribution hitches. Their only reason is that if the hitch is adjusted wrong it becomes a safety issue. I've called them about it and can't get a better explanation. I've checked with a Reece hitch installation vendor and they also couldn't answer the question. They actually install weight distribution hitches on Ridgelines. There are many on the road using WDHs with great success, and of course, many that warn against their use. I'm getting dizzy just typing about it, but Honda's recommendation is the reason I checked with Anderson about the weight necessary for the sway to be effective. I can use very little weight distribution (100 lbs) and still get the advantages of sway control.
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Old 10-30-2013, 03:59 PM   #18
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Originally Posted by TAfraser View Post
Honda recommends against the use of weight distribution hitches. Their only reason is that if the hitch is adjusted wrong it becomes a safety issue. I've called them about it and can't get a better explanation.
That's enough for me. Personally, I would just keep the tongue weight down to 500 pounds, but a properly adjusted WDH is fine, too.

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... I checked with Anderson about the weight necessary for the sway to be effective. I can use very little weight distribution (100 lbs) and still get the advantages of sway control.
I agree - some WD designs, especially the Anderson No-Sway, would need very little WD action to exert substantial sway control.
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Old 10-30-2013, 04:03 PM   #19
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Yes, but remember, the heavier the tongue, the less sway probability.
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Old 10-30-2013, 06:17 PM   #20
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Yes, but remember, the heavier the tongue, the less sway probability.
Yes, if everything else is equal. Tongue weight is not the only factor: a trailer with higher tongue weight will be no more stable if it also has mass distributed out at the ends (for instance - big batteries and generator on the tongue, cargo box on the back).

This is another of the many factors that a simple calculator or a fixed limit can't account for. Tow vehicle GCWR is normally based only on drivetrain reliability, and except possibly when tested according to SAE standard J2807, the trailer weight rating is based on GCWR, tongue weight, and sometimes a guess at the likely stability-limited capacity for some sort of assumed "typical" trailer.
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