Forum Discussion

Community Alumni's avatar
Community Alumni
Jul 04, 2014

Can the weight police check these numbers for me?

I recently acquired a new TV to pull my 21' TT and I have some numbers that I would like to share with the experts here to see what they think.

The TV is a 2014 Jeep Grand Cherokee with the following specs:

6,200 lb towing capacity

6,500 lb GVWR

1,270 lb payload

4,880 lb curb weight with a full gas tank

2,540 lb front & 2340 lb rear per CAT scale

3,200 lb front & 3,700 lb rear GAWR


9,740 lb combined weight of the TV and TT, fully loaded with WDH and gas tank 1/3 full per CAT scale

2,620 lb front, 3060 lb rear & 4,060 lb TT per CAT scale

From what I gather, it seems that I'm well within the maximum limits but I'm a bit confused regarding the discrepancy between the GVWR and payload capacity based on the curb weight.

If the GVWR is 6,500 lbs and the curb weight is 4,880 lbs, logic would dictate the payload should be 1,620 lbs instead of the 1,270 factory rating. Am I missing something in the equation, or it's not unusual to have these types of discrepancies with the specs?

If you look closely, the WDH shifted 80 lbs to the front axle. Do you think that's adequate, or should I adjust the WHD to add more weight to the front or get rid of the 80 lbs. As it is right now, both the TV and TT are fairly leveled.

As always, I'm looking forward to hearing from the experts.
  • No, the 800# increase in TV GVW is not a measure of the TW.

    The estimated 90# of gear and 55# of WDH added to the TV after the first weighing makes the TW appear to be greater than actual.
    The estimated 100# of fuel not included in the second weighing makes the TW appear to be less than actual.
    The amount of load transferred to the TT's axles via the WDH makes the TW appear to be less than actual.

    You cannot calculate the TW using only the information provided, because the amount of load transferred to the TT's axles is unknown.

    If the weight of gear and WDH which was added and the weight of 2/3 tank of fuel which was removed is properly accounted for,
    the indicated increase in hitch load is 800-(90+55)+100 = 755#.

    However, the TW is not equal to the increase in hitch load.
    The TW is equal to the increase in hitch load PLUS the amount of load transferred to the TT's axles.

    The amount of load transferred cannot be determined from the information provided.
    Therefore, the tongue weight cannot be determined from the information provided.

    Ron


    Regardless what the transfer weight is that is his tongue weight... If he disconnects the WD he will just get his TW without WD.

    Example: My tongue weight with WD active is 340. Without 420. Im transfering 80 lbs to TT..

    The transfer dont matter much really. If I do the math of truck alone minus TV, and TT with WD activated I get the same # 340.

    So not understanding what your saying...

    I understand that adding or subtracting more weight changes things, but at least its a base line with all his gear....
  • lawrosa wrote:
    So not understanding what your saying...
    For a given loading condition, a trailer will have only one value of tongue weight.
    That value is the number you would get from a scale placed directly under the ball coupler with the trailer level -- and with no WD applied.
    It is this value, when divided by the trailer's loaded weight, which gives the tongue weight percentage.

    The amount of load transferred to the trailer's axles is important because it can be equal to as much as 20-30% of the trailer's loaded weight.
    If a loaded trailer weighs 8000# and the correct tongue weight is 1000#, the tongue weight percentage would be calculated correctly as 1000/8000 = 12.5%.

    If the WDH is adjusted to transfer 250# (25% of tongue weight) to the trailer's axles, the measured hitch load (as opposed to tongue weight) would be 750#.

    If you used the hitch load divided by the trailer's total weight to attempt to determine the tongue weight, you would get a quotient of 750/8000 = 9.4%.
    And, if you believed the tongue weight percentage really was 9.4%, you probably would conclude the TW% is much lower than it should be -- when, in fact, it is at the 12.5% value which many consider to be close to optimum.

    IMO, "tongue weight" is only determined when the WD is NOT activated.
    If load measurements are taken with WD activated, the calculated increase in TV GVW should be referred to as "hitch load" and should not be confused with "tongue weight".

    Ron
  • Why is:

    1. Under FAWR
    2. Under RAWR
    3. Under GVWR
    4. Under GCVWR
    5. Under factory "tow rating"
    6. Under factory "payload capacity"
    7. Under receiver rating

    NOT GOOD ENOUGH????

    The truth of the matter is, ***IT IS PLENTY GOOD ENOUGH***, near perfect in fact, and if he's happy with how it tows, GO CAMPING!
  • mkirsch wrote:
    Why is:

    1. Under FAWR
    2. Under RAWR
    3. Under GVWR
    4. Under GCVWR
    5. Under factory "tow rating"
    6. Under factory "payload capacity"
    7. Under receiver rating

    NOT GOOD ENOUGH????

    The truth of the matter is, ***IT IS PLENTY GOOD ENOUGH***, near perfect in fact, and if he's happy with how it tows, GO CAMPING!


    It could be "good enough". But it may not be "optimum".
    Example: when I was setting the WD on my smaller truck and camper, I was within all limits, but was in fact transferring more load to the steer axle than was optimum. And I could feel it in the steering. Once I backed off a little bit of the load transferred, the truck felt and handled better. To me, that was the difference between good enough, and optimum.
    The scales tell the story. YMMV.
  • 80lbs extra on the front axle, he almost certainly does not even notice.

    That's a fat guy in the front passenger seat.
  • mkirsch wrote:
    80lbs extra on the front axle, he almost certainly does not even notice.
    That's a fat guy in the front passenger seat.
    Having a front-seat passenger add load to the front axle is totally different from having a WDH add load to the front axle.
    Here's what some credible sources have to say about adjusting the WDH to restore too much load to the front axle.

    I think the reason Ford, Chevrolet, Toyota, Equal-i-zer, Reese and others have changed their weight distribution specifications is pretty well summed up in this Letter to Editor by Richard H Klein, P E printed in TRAILER BODY BUILDERS Magazine. The comment which specifically addresses front axle load is:

    QUOTE

    2. The statement “too much tongue weight can force the truck down in the back, causing the front wheels to lift to the point where steering response and braking can be severely decreased” is not the real issue with heavy tongue weights. The real problem is that the tow vehicle's yaw stability, as measured by “understeer gradient”, is severely decreased. This increases the propensity of the tow vehicle to jackknife in turning maneuvers. Specifically, recent full scale testing conducted by the SAE Tow Vehicle Trailer Rating Committee (and now published in SAE J2807), determined that the use of weight distributing hitch torque should be minimized. In fact they recommend that the Front Axle Load Restoration (FALR) not exceed 100% (100% means that the front axle weight is brought back, via weight distribution, to a weight equal to its “no trailer” condition).


    UNQUOTE

    A related explanation from a representative of the company which manufactures the Equal-i-zer hitch was first posted here. It says:

    QUOTE

    In the past we had suggested that you should see a small drop on the front suspension. We are always trying to improve things here at Progress – our motto is “Safe and Happy Customers,” and so we are always reviewing our instructions and installation process. Recently, as part of this constant effort our engineers looked more deeply into this aspect of installation. We had always felt that a small drop was a sign that the trailer’s weight was being transferred to the front axle, and that this was essentially a good thing.

    As our engineers reviewed the instructions for the last round of renewal of our instructions, the found research results that contradicted our prior thinking. There has been a substantial amount of testing conducted by experts from SAE and the RV Industry Association to find out what will produce the best stability when towing. This towing suggests that you want your front axle’s compression to be close to, but not lower than your free-standing height.

    (Underline added for emphasis.)
    UNQUOTE

    Ford says the Front Axle Load Restoration should be approximately 50%.

    Chevrolet/GMC says the FALR should be 100%, 50% or 0% depending on TV model and TT weight.

    Equal-i-zer says the Front Axle Load Restoration should be between 50% and 100%.

    Equal-i-zer's revised instructions specifically state:

    Good adjustment:
    You have most likely achieved good weight distribution adjustment if your measurements show the following with the trailer coupled and the weight distribution engaged:
    1. From the coupled without weight distribution measurement, the front wheel well measurement is at least halfway back to the original uncoupled measurement. See line C on Front Wheel Well Measure Chart.
    2. The rear wheel well measurement is somewhere between the uncoupled height, and the coupled with no weight distribution height. It should NEVER be higher than the uncoupled height. See line C on Rear Wheel Well Measure Chart. See Figure 19.



    Ron
  • Curious how all these revised specs. using fender height relates to using weights from a scale? I thought using scale weights is a more accurate method? Or would you adjust fender height first and then go to a scale to fine tune?
  • You thought correctly. :)
    The fender height method just gets you in the ballpark. To be accurate and sure you must go to a scale.
    Barney

About RV Tips & Tricks

Looking for advice before your next adventure? Look no further.25,102 PostsLatest Activity: Jan 18, 2025