Another TM weight measurement

[Bill]

[I apologize for the techie nature of this post, but the good stuff is right at the top, and the preachy stuff is at the bottom.]

My wife and I recently made our annual pilgrimage from our winter haunt in Arizona to our summer place in Maine. As we started out, we weighed the rig on a CAT scale. As usual, the CAT scale took only 10 minutes and $10, and gave the following results:

Position..............CAT wght......Rated wght
F-150 front axle.....3400..........3900 (sticker on driver's door)
F-150 rear axle......3940..........3850 (sticker on driver's door)
TM axle................3360..........3500 (axle limit) - 4760@60 psi (tire limit)
Total wght......10,700 pounds (this is the gross combined weight of the rig)

Weighing Conditions:
TM 2720SL
No black, gray, or fresh water
6 gallons of water in the water heater
About 10 pounds of propane in one tank, other tank empty.
Two people in the front seat of the F-150 tow vehicle.
Lots of stuff in the F-150 bed, including a 300-pound table saw (don't ask).
WDH cranked up to our normal travel position.
F-150 tires - Goodyear Wrangler SR-A P275/65R18

Sidewall says max load = 2601 pounds at max pressure 44 psi cold
Actual cold pressure about 41 psi​

TM tires - Goodyear Marathon ST225/75R15

Max load = 2540 pounds at max pressure 65 psi cold
Actual cold pressure about 60 psi​

F-150 ratings taken from driver's door sticker

So it looks like everything was OK for our rig. The F-150's rear axle was a bit overloaded, which surprised me since this is a fairly big truck. I should have moved 100 pounds of stuff. But nothing else was over its rating, and the 15-inch tires on the TM had lots of margin. But I noticed one thing. The TM had 3360 pounds on its axle. Since the WDH was engaged, the actual weight of the TM was more than 3360. A bunch of calculations and techie stuff [deleted for your reading pleasure] confirm previous conclusions by other members that the total (gross) weight of my TM was around 3800-4000 pounds, and even worse if I had carried water in the tanks. [Water weighs 8-1/2 pounds per gallon.] This is why I get nervous about towing a TM with a tow vehicle rated at 3500 pounds - especially when you remember that the tow vehicle's tow rating is decreased by the weight of everything you put in it, including cargo and passengers. If you put 400 pounds of people and cargo in your tow vehicle, the 3500-pound rating becomes 3100 pounds. Towing a 3800- or 4000-pound trailer doesn't seem like a good thing to do, even if you "never had a problem" doing it.

It also suggests that without a WDH, the hitch weight of my TM would be on the order of 560 pounds, which exceeds the 500-pound rating of most weight-carrying hitches. So again I get nervous about not using a WDH unless your hitch rating is at least 600 pounds.

Bill

 

[Larryjb-HILO]

Towing rig: 2002 Chevrolet Tahoe
On our trip to Kamloops summer 2017
No WDH

Position..........Wgt.....Rated wgt
Front axle.......2860....???? (I have to look it up again)
Rear axle........4158....3960
trailer axle......3498....3500
Total: 10050

I thought we had over packed horribly. Compared to Bill who has far more experience, actually comes in about 650 lbs heavier. Now, Bill's F-150 could be heavier than the Tahoe, depending on what F150 he has. My Tahoe is around 5000 lbs. Considering Bill's experience, I don't think we did too badly. The WDH would have removed some weight off the rear axle, but transferred some to the trailer axle, overloading the trailer axle. Bill travelled without water. We travelled with 2 flats of bottled water in the trailer, plus a ton of canned food. Removing this, or putting it in the rear of the Tahoe would have worked out well with a WDH.

Bill, your numbers just go to exemplify just how easy it is to overload a trailer, even with experience. If you are going to pull with a unibody style SUV, you have to pack much lighter as most unibody style SUVs out there have a lower towing rating.

 

[MBushaw]

Bill, you got me confused.
I’m assuming that you weighed with everything connected.
Wouldn’t this ADD weight to the TM axle? I thought that a wdh shifted weight from the hitch to front of TV and also to TM axle.
But then you say that the TM axle was actually heavier than weighed.
How does that figure?

Thanks
Mark

[I apologize for the techie nature of this post, but the good stuff is right at the top, and the preachy stuff is at the bottom.]

My wife and I recently made our annual pilgrimage from our winter haunt in Arizona to our summer place in Maine. As we started out, we weighed the rig on a CAT scale. As usual, the CAT scale took only 10 minutes and $10, and gave the following results:

Position.....CAT wght....Rated wght (sticker on driver's door)
Front axle.....3400.........3900
Rear axle......3940.........3850
TM axle........3360.........3500 (axle limit) - 4760@60 psi (tire limit)
Total wght..10,700 pounds (this is the gross combined weight of the rig)

Weighing Conditions:
TM 2720SL
No black, gray, or fresh water
6 gallons of water in the water heater
About 10 pounds of propane in one tank, other tank empty.
Two people in the front seat of the F-150 tow vehicle.
Lots of stuff in the F-150 bed, including a 300-pound table saw (don't ask).
WDH cranked up to our normal travel position.
F-150 tires - Goodyear Wrangler SR-A P275/65R18

Sidewall says max load = 2601 pounds at max pressure 44 psi cold
Actual cold pressure about 41 psi​

TM tires - Goodyear Marathon ST225/75R15

Max load = 2540 pounds at max pressure 65 psi cold
Actual cold pressure about 60 psi​

F-150 ratings taken from driver's door sticker

So it looks like everything was OK for our rig. The F-150's rear axle was a bit overloaded - I should have moved 100 pounds of stuff - but nothing else was over its rating, and the 15-inch tires on the TM had lots of margin. But I noticed one thing. The TM had 3360 pounds on its axle. Since the WDH was engaged, the TM actually weighed more than 3360. A bunch of calculations and techie stuff [deleted for your reading pleasure] confirm previous conclusions by other members that the total (gross) weight of my TM was around 3800-4000 pounds. This is why I get nervous about towing a TM with a tow vehicle rated at 3500 pounds - especially when you remember that the tow vehicle's tow rating is decreased by the weight of everything you put in it, including cargo and passengers. If you put 400 pounds of people and cargo in your tow vehicle, the 3500-pound rating becomes 3100 pounds. Towing a 3800-pound trailer doesn't seem like a good thing, even if you "never had a problem doing it". And even worse if you tow with water in your tanks.

It also suggests that without a WDH, the hitch weight of my TM would be on the order of 560 pounds, which exceeds the 500-pound rating of most weight-carrying hitches. So again I get nervous about not using a WDH unless your hitch rating is at least 600 pounds.

Bill

 

[Larryjb-HILO]

Mark,

I didn't catch that when I first read it either. It still holds true that the gross weight of his TM is actually heavier than the 3360, but this is simply because the 3360 is the axle weight. The rest of the gross trailer weight is on the hitch. Without a WDH, his TM axle weight should be less than 3360, but his TV rear axle would be over the limit even more.

Two other points Bill made that I want to reiterate because I think they are ignored for forgotten about:

1) Cargo and people in the TV reduce your towing limit. If the rated towing limit is equal to a dry TM, (say 3500 lbs), as soon as you add the driver and family you are now over the limit by at least 400 lbs.

2) Check your individual axle weight limits, especially the rear axle of your TV. Given that the TM is heavier than most on the hitch, it is very easy to exceed the rear axle rating of your TV.

 

[MBushaw]

Ahhh!
Thanks Larry.
I guess once you get the empty weight of the individual parts ( wdh hooked to TM only) once, it is easier to do the math the next time.

 

[Bill]

If anybody cares --
The techie stuff and calculations that I removed from the original post go like this.

Assume that my total trailer weight is 3800 pounds
. . This is the dry weight of the trailer, plus the factory options and any aftermarket options, plus all the stuff I packed onto it.
Assume that a TM puts 14% of its gross weight on the hitch = 532 pounds
. . This is more than the standard 10% recommended by trailer experts. It came from the TM factory in Tennessee.
. . This is what makes a TM so sway-resistant.
The TM axle weight without a WDH would have been = 3800 - 532 = 3268
The TM axle weight with the WDH (measured) = 3360
Therefore the WDH shifted 3360-3268 = 92 pounds from the hitch ball to the TM axle, and took this weight off the tow vehicle's rear axle.
. . It also shifted a similar amount of weight from the hitch ball to the tow vehicle's front axle.
. . Taking weight OFF the rear axle, and adding it TO the front axle is what levels the tow vehicle.

Obviously I didn't have the WDH cranked up very high. It would have been interesting if I had cranked the hitch up one more link, and then weighed again. But I didn't.

This illustrates how the WDH moves weight from the tow vehicle rear axle to back onto the TM axle.

Bill