The Benefits of Weighing Your Tow Rig Twice

[DW-gray]

So often, RVers will pull up to a scale and get the weight of the tow vehicle's front and rear axles, and the trailer axles. They drive away, and later sit down with their calculator to come up with few safety weight numbers. It either looks good or they may discover a truck axle that's overloaded or maybe they exceed the gross combination weight rating (GCWR). They think that's it and that's all they need to know.

RV Safety and Education Foundation (RVSEF) data indicates that 60 percent of all tow vehicles on the road exceed one or more weight safety ratings. "Many of these trucks exceed all of their ratings," said Walter Cannon, executive director of RVSEF.

The following RV rig reports are based on a real towing combination with a fifth wheel that speaks more volumes than a bunch of words. (Conventional tow rigs may require up to three weigh-ins when using weight distribution systems.)

(The examples below are not my rig.)


Here is all one can know with one weigh-in.





Here is the report with two weigh-ins.

[BubbaChris]

I had a mobile check done last year, here's the report I got

[PA12DRVR]

"If it was a CAT scale and you had positioned your rig correctly the print-out they give you should have had the axle weights."

This^^^^. Steer, Drive, Trailer weights provided separately.

Answers all the questions one needs to know without multiple positioning.

I did this once with the DW helping me (she drove while I waited at the CAT counter)....spent $40 (for multiple weighs) chasing a 135# discrepancy only to realize that, ahem, that was the difference between me being the driver (vs. off-scale observer) and the DW being the driver.

[C-Bears]

I guess I am approaching it from a full timers prospective. I really don't want to make a special trip to a scale, and I sure don't want to be unhooking and hooking up my "home" in some truck stop parking lot.

I visit Flying-J or Pilot stations all the time to get fuel anyway. It only takes a few minutes, no matter if I am towing or not, to pull over the scale.

[Javi1]

Or you could just use a really big TV.. 😄


Nice chart though.. I opted for the too big enough truck..

[RCMAN46]

OutdoorPhotographer wrote:
Thanks. Chart helped a lot. You're not having to reposition the tow vehicle for different weights, just ensure each axle is at the appropriate place on the scales and get different measurements. I'm sure the scales I've used before had the different plates, I just never needed axle weights so I didn't know to ask.

If it was a CAT scale and you had positioned your rig correctly the print-out they give you should have had the axle weights.

If you are weighing on a single bed scale tell the operator you will need three individual weights.

Then pull on the scale with only front TV axle on scale. When the operator signals you usually with a light system similar to a traffic light pull forward until both TV axles are on the scale. Then last pull all axles onto the scale.

From those three weights you can calculate the individual axle weights.

Then with a 5th wheel I drop my trailer in a safe out of the way location and go back it do the same with the TV.

Now I have all the information I need to determine if I have enough pin weight percentage and if all of my axles are in limits. Do not forget the tire ratings.

If it is a pull trailer it will require (three trips across the scale) doing the first part first with WD engaged and then second with WD dis-engaged and then without the trailer.

[ependydad]

DW-gray wrote:

C-Bears wrote:
That gets pretty confusing. I use this site/formula.

http://www.towingplanner.com/ActualWeights/FifthWheelCatScales

What’s confusing?

The site you mentioned does give six important weight results. The difference is on that site, if one wants to know their margins based on their vehicles’ weight ratings, one will have to pull out their calculator and calculate the numbers.

You're right and I do that to keep the site simple. I wrote these tools because I found most online calculators were overwhelming as I first got into figuring out weights and what I could tow within the manufacturer's posted ratings.

[OutdoorPhotogra]

Thanks. Chart helped a lot. You're not having to reposition the tow vehicle for different weights, just ensure each axle is at the appropriate place on the scales and get different measurements. I'm sure the scales I've used before had the different plates, I just never needed axle weights so I didn't know to ask.

[DW-gray]

OutdoorPhotographer wrote:
Pardon my ignorance but how do you get axle weights from one weigh-in? I only pull a pop-up with a F-150 with tow package so not a real problem today but as I get closer to retirement I'm looking to move to bigger trailers and tow vehicles and starting to learn the new language with a 5th wheel.

I've used scales many times to weigh vehicles but have not weighed a trailer combo. I've always just received a gross weight, not by axle. Do I simply need to ask for a more detailed measurement?

Trailer axle weights are obtained by weighing only the trailer axles on the scale while it is connected to the tow vehicle.

Here is a link to a 5th wheel worksheet for weighing at CAT Scale: 5th Wheel Weighing Worksheet at CAT Scale

[OutdoorPhotogra]

Pardon my ignorance but how do you get axle weights from one weigh-in? I only pull a pop-up with a F-150 with tow package so not a real problem today but as I get closer to retirement I'm looking to move to bigger trailers and tow vehicles and starting to learn the new language with a 5th wheel.

I've used scales many times to weigh vehicles but have not weighed a trailer combo. I've always just received a gross weight, not by axle. Do I simply need to ask for a more detailed measurement?

[DW-gray]

C-Bears wrote:
That gets pretty confusing. I use this site/formula.

http://www.towingplanner.com/ActualWeights/FifthWheelCatScales

What’s confusing?

The site you mentioned does give six important weight results. The difference is on that site, if one wants to know their margins based on their vehicles’ weight ratings, one will have to pull out their calculator and calculate the numbers.

[DW-gray]

Golden_HVAC wrote:
So was that the readout for your truck and trailer?

That would put the pin weight around 3,200 pounds on your trailer. Is that including your smart car in the back, or without it? It seems like with the smart car, the pin weight would go down by say 200 to 300 pounds or so.

Also interesting is that the front axle weight is about 150 pounds higher with the trailer attached. It seems like with the hitch pin centered over the axle and 1" to 2" forward, only a small portion of the trailer pin weight would transfer to the truck front axle. In this case the truck GVW went from 7700 to 10,900 pounds or up by 3,200 pounds. 5% (would be 160 pounds) is transferred to the front axle.

All of this is very interesting.

Fred.

Excellent observations, Fred. It’s certainly observations one would not see with just only one weigh-in.

No, the example above is not my rig. (I added a note above to that fact.) But you do point out correctly that pin weight is usually reduced when heavy items are garaged in toy haulers. In my toy hauler, the pin weight is reduced by 325 pounds. (From 3,725 to 3,400)

The reason that there appears to be a sight weight error for the weight shift is likely in the scales. Most scales for heavy weighing only have divisions of 20 or 50 pounds. Therefore, the potential for error is 10 pounds for 20 pound division and 25 pounds for 50 pound division.

[C-Bears]

That gets pretty confusing. I use this site/formula.

http://www.towingplanner.com/ActualWeights/FifthWheelCatScales

I try to do my weights twice a year and plug all the information in. I never unhook at the scales. I generally will weigh my truck by itself a day or two before pulling out when I am at a Pilot or Flying J toping off my tanks. Then during one of my first fuel stops down the road pulling the FW I will run across the scales again hooked up. Then I will take the two weight tickets and enter the information into the aforementioned formula.

[Golden_HVAC]

So was that the readout for your truck and trailer?

That would put the pin weight around 3,200 pounds on your trailer. Is that including your smart car in the back, or without it? It seems like with the smart car, the pin weight would go down by say 200 to 300 pounds or so.

Also interesting is that the front axle weight is about 150 pounds higher with the trailer attached. It seems like with the hitch pin centered over the axle and 1" to 2" forward, only a small portion of the trailer pin weight would transfer to the truck front axle. In this case the truck GVW went from 7700 to 10,900 pounds or up by 3,200 pounds. 5% (would be 160 pounds) is transferred to the front axle.

All of this is very interesting.

Fred.