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Open Roads Forum  >  Towing

 > Payload Capacity and Tongue Weight

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thomas malenich

sound beach, new york 11789

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Posted: 09/17/04 12:24am Link  |  Print  |  Notify Moderator

Auto manufacturers base their towing capacities on a vehicle's base curb weight. Optional equipment is not included in this weight. This figure is of little use when trying to determine your payload. Knowing your actual payload capacity will keep you from exceeding your gross vehicle weight rating(GVWR).

To determine your available payload, first weigh your tow vehicle(TV), unless you have an accurate delivery weight. With the actual weight figure, add the weight of your family including yourself, a full tank of fuel, and the cargo you would carry in your TV. Subtract that total from your GVWR and you now have the remaining available payload (what is left for tongue weight).

The maximum TW you can add to your TV will depend on whether or not you use a weight distribution(WD) hitch, sometimes called an equalizing hitch. A WD hitch removes some of the load from the TV's rear axle and distributes it to the TV's front axle and the TT's axle(s). Check with your manufacturer to be sure that you can use a WD hitch as it puts stress on the TV's components.

If you do not or can not use a WD hitch, all of the TW gets applied to your remaining payload capacity. If you exceed this, then you have exceeded your GVWR. Furthermore approx. 150% of the TW will be added to your rear axle(the extra 50% is front axle weight distributed to the rear axle). This could exceed your rear gross axle weight rating(GAWR). The load on your front axle will be reduced by 50% of the TW and both steering and braking would be compromised. Be aware of the hitch ratings on your TV. There will be a lower rating when not using a WD hitch. Always be sure that your tires are rated for your GVWR at proper inflation.

If you use a WD hitch and utilize appropriate spring bar tension(SBT), then you can expect to apply only about 67% of TW (+ the weight of the WD hitch itself) to your payload capacity. Total SBT in pounds should be equal to double your tongue weight. Approx. 33% of the TW is distributed to the TT axles(s) and the load on the receiver will be reduced by approx. 33%. The load on the rear axle of your TV will only be about 50% of the TW.

EXAMPLE:

TV base curb weight - 5546#s
TV fully loaded - 6500#s
GVWR - 7200#s
Remaining payload capacity - 700#s (GVWR - 6500#s)
GAWR (rear) - 4000#s
Receiver Cap. - 500#s weight carrying / 1000#s WD
SBT - 2000#s total
WD Hitch - 100#s
Tongue Weight of your dream TT - 900#s

Without a WD hitch the 900# TW will overload the remaining payload capacity (700#s) and the GVWR (7200#s) by 200#s. The receiver hitch rating is overloaded and the rear GAWR will probably be overloaded as well as there would be an increase of 1350#s on the rear axle.

With a WD hitch, the TW will increase by the weight of the hitch itself to 1000#s. This would put 670#s(67% of TW) onto the TV and be just under the remaining payload capacity. The hitch capacity rating is now 1000#s, so you are OK there as well. There will only be a 500# increase on the rear axle(50% of TW). About 170#s (17% of the TW) will be on your front axle, as steering and braking dynamics are much less affected.


Using a WD hitch in this example would keep you inside of your capacities, but towing performance might not be great. Towing performance is somewhat subjective, but most members recommend that you tow at 80% of your capacities. It is very important to take into consideration the engine size and rear axle gear ratio. Towing near 100% of your capacities can lower the normal lifespan of your engine, transmission, and other components. It is always best to take actual weight readings of your TV, TT and individual axles. It is also possible to exceed the gross combined weight rating(GCWR) and not exceed the GVWR.


NOTE:
Travel Trailer manufacturers generally base their trailer weight and tongue weight on a base unit with little or no options. They call it the unloaded vehicle weight(UVW) and will provide the dry TW or dry hitch weight. To get your actual TT weight add the weights of all options not included in the UVW, full propane, weight of battery, and weight of a full fresh water tank. To get the actual loaded TT weight you will need to estimate the weight of your gear and food. The actual loaded TW will generally be between 10% and 15% of the loaded TT weight depending on the manufacturers axle placement and how you load it.



Edited 9/23/04: The above results using a WD hitch represent an attainable goal. The weight distributed back to the TT axle(s)is dependent on adequate spring bar tension, the length of the spring bars, the distance from the hitch ball to the spring bar attachment location and the distance from the hitch ball back to the TT axles. These variables will change the end result. Other factors such as wheelbase and rear overhang will affect how the TV axle weights are distributed.

* This post was last edited 09/23/04 09:44pm by thomas malenich *   View edit history


Thomas and Laura Malenich
1988 Suburban 1500, 4WD
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DavidG

Jacksonville, FL

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Posted: 09/17/04 10:46am Link  |  Print  |  Notify Moderator

Tom,

An excellent and detailed post!

However, my experience is different than what your numbers suggest.
Quote:

If you use a WD hitch and utilize appropriate spring bar tension(SBT), then you can expect to apply only about 67% of TW (+ the weight of the WD hitch itself) to your payload capacity. Total SBT in pounds should be equal to double your tongue weight. Approx. 33% of the TW is distributed to the TT axles(s) and the load on the receiver will be reduced by approx. 33%. The load on the rear axle of your TV will only be about 50% of the TW.
The last time I had my combo on the scales I had 1050# of tongue weight. The front end of the truck lightened up 280# and the rear gained 1180# for a net difference of 900#. I didn’t weigh the trailer axles, but assume the other 150# (1050-900) went back to the TT axles. This is with the hitch head tilted almost all the way back (7 washers), spring bars parallel to the frame and trailer 1/2” lower in the front than the back. I added the last washer, but it only made a 20# difference and was extremely difficult to get the chains snapped up, so I went back to 7 washers.

Percentage-wise, this means that for my setup (Eaz-lift, 1400# bars), about 85% of the 1050# tongue weight ended up on the TV and 15% (not 33%) back on the TT, and 112% (not 50%) of the tongue weight ended up on the TV’s rear axle.

Your numbers may reflect what “should” happen with the weight, but given all of the variables in the equation (spring bar tension and how to measure it, hitch head angle relative to perpendicular, tow vehicle suspension and wheelbase, and others), what “really” happens could be a lot different. Your numbers and percentages could be “ideal” numbers, but they may not be attainable for some (like me).

Unless you have a very light tongue weight and an over-rated WD hitch (mainly the spring bars), I don’t see how you could achieve only 50% of the tongue weight on the TV rear axle.


David and Laura G
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BenK

SF BayArea

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Posted: 09/17/04 11:01am Link  |  Print  |  Notify Moderator

Agree with Tom's comments, but need to add a few additional variables, IMHO.

The percentages of weights is variable or dependent on the vehicle in question. Meaning the distances (lever arms) from the TV's rear axle center of load to the hitch ball. The hitch ball to the TT's axle(s) center of load. Even the TV's wheel base factors on how much the front end lifts or not.

The 80% of rated "max trailer weight rating" (MTWR) is a good rule of thumb but is another that is variable dependent on the vehicle in question. Meaning the "stripper" model level compared to the actual TV weight. Then the type of TV, as a full sized SUV can be loaded up to it's GVWR easier than a pickup...though some would argue that one

The bottom line is the gamble that everyone takes with their margins...aka safety factors. Know your weights, "true" ratings and HOW2 setup your systems. Weigh your setup axle by axle, empty and fully loaded. Do your own math and keep good records.


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

thomas malenich

sound beach, new york 11789

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Posted: 09/17/04 11:41am Link  |  Print  |  Notify Moderator

Ben and David,

I agree that things do not always end up as you hope or plan on paper. I should have said that the results using a WD hitch represent an attainable goal. The weight distributed back to the TT axle(s)is dependent on adequate spring bar tension as I said, but also the length of the spring bars, the distance from the hitch ball to the spring bar attachment point and the distance from the hitch ball back to the TT axles. These variables will change the end result. Other factors such as wheelbase and rear overhang will affect how the TV axle weights are distributed. Thank you both for pointing this out.

thomas malenich

sound beach, new york 11789

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Posted: 09/17/04 12:13pm Link  |  Print  |  Notify Moderator

The last time I had my combo on the scales I had 1050# of tongue weight. The front end of the truck lightened up 280# and the rear gained 1180# for a net difference of 900#. I didn’t weigh the trailer axles, but assume the other 150# (1050-900) went back to the TT axles. This is with the hitch head tilted almost all the way back (7 washers), spring bars parallel to the frame and trailer 1/2” lower in the front than the back. I added the last washer, but it only made a 20# difference and was extremely difficult to get the chains snapped up, so I went back to 7 washers.

Percentage-wise, this means that for my setup (Eaz-lift, 1400# bars), about 85% of the 1050# tongue weight ended up on the TV and 15% (not 33%) back on the TT, and 112% (not 50%) of the tongue weight ended up on the TV’s rear axle.
____________________________________________________________________

David, Did you add the weight of your WD hitch into the mix? In other words does your 1050# TW figure include the weight of your WD hitch? If not then you might not be that far off. Let's say your WD hitch weighs 175#s (it is a 1400#er). Add 175#s to 1050#s and you get 1225#s of tongue weight. 33% of 1225 is 404#s that could go back to the TT. 67% of 1225 is 820#s that would be on your TV - not far off from your 900#s.

Using your results of 900#s on your TV - you would have about 74% of tongue weight on your TV and 26% would be reflected on your TT axles.

* This post was last edited 09/17/04 03:52pm by thomas malenich *   View edit history

DavidG

Jacksonville, FL

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Posted: 09/17/04 01:54pm Link  |  Print  |  Notify Moderator

To be honest, I don’t remember (it was some time ago). I’ll have to see what it weighs, but 175# sounds a little high.

Retired Coastie

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Posted: 12/23/04 08:21pm Link  |  Print  |  Notify Moderator

One very minor issue. I used a magnifying glass to read the fine print on my K2500HD Chevy. GVWR includes a full tank of gas. If you had a half tank of gas, you could add the difference to Payload.


Larry Pierce 2004 2500HD, X-cab, LWB, 4X4, 6.0 gasser. 265Es, IPD anti-sway bar, Rancho 9000s, Ride-Rite bags,

2003 NL "Northern" 9' - 6" w/ Honda 2000i, Polar Cub 9200 btu a/c, 40W solar, other goodies.

2002 Fisher 18 1/2 ft, 115 Merc, 24V Minn-Kota.

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