Forum Discussion

rvhippo's avatar
rvhippo
Explorer
Jan 09, 2014

Tongue Weight, Leverage and RGAWR

I tried google-ing but couldn't find anything, so I'm turning to the collective expertise here.

Question: Tongue weight is applied at the hitch, which is a distance from the rear axle. Because of the distance, the weight should be magnified at the rear axle. Is there any easy way to predict what the axle loading will be?

I am trailer shopping and have about 800 lbs. left on GVWR and maybe 900 lbs. left on the RGAWR.

What I'm worried about is that I get a trailer with a tongue weight of 650-700 lbs. and when I go get the whole rig weighed, the leverage from the hitch ends up making me exceed my RGAWR. How do you return a trailer?

Now, throw in whatever effects a WD hitch will have on weight distribution between all the axles.

Does anyone have any practical advice? Does the weight-multiplication effect of leverage from the distance between the rear axle and the hitch get balanced out by the WD hitch?

Thanks in advance.

-edit for bad grammar-
  • APT's avatar
    APT
    Explorer
    Jan 09, 2014
    camp-n-family wrote:
    You can usually count on approximately 40% of the tongue weight to be transferred off the rear axle if the hitch is set up properly. Half of that would get distributed back to the TVs front axle, the other half onto the TT. Only way to know how much for sure is to get it weighed, as all trucks, trailers and hitch set ups will behave differently.


    Just to be clear, it is not 40% of tongue weight.

    So using the OP's 800 pounds of TW as an example:
    Dropping the tongue on the ball will add about 1100 pounds to the rear axle weight and remove 300 pounds from the front axle. Adding a WDH and adjusting such that the front axle is back to unhitched weight will cause the rear axle to increase about 650 pounds over unloaded and trailer axles increase by about 150 pounds. So 40% of 800 pound TW is not removed from the rear axle. About 40% of the added rear axle weight will. 60% of 1100 pounds = 650.
  • Ron_Gratz's avatar
    Ron_Gratz
    Explorer
    Jan 09, 2014
    rvhippo wrote:
    Does anyone have any practical advice? Does the weight-multiplication effect of leverage from the distance between the rear axle and the hitch get balanced out by the WD hitch?
    The amount of load added to the rear axle depends on:
    Trailer tongue weight (TW)
    Distance from TV rear axle to ball (D2)
    Distance from ball coupler to midpoint between trailer axles (D3)
    How you adjust the WDH

    If you adjust the WDH to restore 100% of the load which was removed from the TV's front axle,
    the net load added to the TV's rear axle will be:

    Added Load = TW*D3/(D2+D3)

    Ron
  • camp-n-family's avatar
    camp-n-family
    Explorer
    Jan 09, 2014
    You can usually count on approximately 40% of the tongue weight to be transferred off the rear axle if the hitch is set up properly. Half of that would get distributed back to the TVs front axle, the other half onto the TT. Only way to know how much for sure is to get it weighed, as all trucks, trailers and hitch set ups will behave differently.
  • rvhippo's avatar
    rvhippo
    Explorer
    Jan 09, 2014
    My google skills are weak.

    I found part of my answer:

    http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/25167213.cfm

    Gives the calculation for weight multiplication at the rear axle due to hitch distance.

    Would it be reasonable to assume that some of this weight is then transferred off the rear axle by a WD hitch?

    Thanks again.

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